From: SeongJae Park <[email protected]>
Changes from Previous Version (v26)
===================================
- Rebase on latest -mm tree (v5.12-rc6-mmots-2021-04-06-22-33)
- Check kmalloc() failures in dbgfs init (Greg KH)
- Fix a typo: s/stollen/stolen/ (Stefan Nuernberger)
- Update document for updated user space tool path
Introduction
============
DAMON is a data access monitoring framework for the Linux kernel. The core
mechanisms of DAMON called 'region based sampling' and 'adaptive regions
adjustment' (refer to 'mechanisms.rst' in the 11th patch of this patchset for
the detail) make it
- accurate (The monitored information is useful for DRAM level memory
management. It might not appropriate for Cache-level accuracy, though.),
- light-weight (The monitoring overhead is low enough to be applied online
while making no impact on the performance of the target workloads.), and
- scalable (the upper-bound of the instrumentation overhead is controllable
regardless of the size of target workloads.).
Using this framework, therefore, several memory management mechanisms such as
reclamation and THP can be optimized to aware real data access patterns.
Experimental access pattern aware memory management optimization works that
incurring high instrumentation overhead will be able to have another try.
Though DAMON is for kernel subsystems, it can be easily exposed to the user
space by writing a DAMON-wrapper kernel subsystem. Then, user space users who
have some special workloads will be able to write personalized tools or
applications for deeper understanding and specialized optimizations of their
systems.
Long-term Plan
--------------
DAMON is a part of a project called Data Access-aware Operating System (DAOS).
As the name implies, I want to improve the performance and efficiency of
systems using fine-grained data access patterns. The optimizations are for
both kernel and user spaces. I will therefore modify or create kernel
subsystems, export some of those to user space and implement user space library
/ tools. Below shows the layers and components for the project.
---------------------------------------------------------------------------
Primitives: PTE Accessed bit, PG_idle, rmap, (Intel CMT), ...
Framework: DAMON
Features: DAMOS, virtual addr, physical addr, ...
Applications: DAMON-debugfs, (DARC), ...
^^^^^^^^^^^^^^^^^^^^^^^ KERNEL SPACE ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Raw Interface: debugfs, (sysfs), (damonfs), tracepoints, (sys_damon), ...
vvvvvvvvvvvvvvvvvvvvvvv USER SPACE vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
Library: (libdamon), ...
Tools: DAMO, (perf), ...
---------------------------------------------------------------------------
The components in parentheses or marked as '...' are not implemented yet but in
the future plan. IOW, those are the TODO tasks of DAOS project. For more
detail, please refer to the plans:
https://lore.kernel.org/linux-mm/[email protected]/
Evaluations
===========
We evaluated DAMON's overhead, monitoring quality and usefulness using 24
realistic workloads on my QEMU/KVM based virtual machine running a kernel that
v24 DAMON patchset is applied.
DAMON is lightweight. It increases system memory usage by 0.39% and slows
target workloads down by 1.16%.
DAMON is accurate and useful for memory management optimizations. An
experimental DAMON-based operation scheme for THP, namely 'ethp', removes
76.15% of THP memory overheads while preserving 51.25% of THP speedup. Another
experimental DAMON-based 'proactive reclamation' implementation, 'prcl',
reduces 93.38% of residential sets and 23.63% of system memory footprint while
incurring only 1.22% runtime overhead in the best case (parsec3/freqmine).
NOTE that the experimental THP optimization and proactive reclamation are not
for production but only for proof of concepts.
Please refer to the official document[1] or "Documentation/admin-guide/mm: Add
a document for DAMON" patch in this patchset for detailed evaluation setup and
results.
[1] https://damonitor.github.io/doc/html/latest-damon/admin-guide/mm/damon/eval.html
Real-world User Story
=====================
In summary, DAMON has used on production systems and proved its usefulness.
DAMON as a profiler
-------------------
We analyzed characteristics of a large scale production systems of our
customers using DAMON. The systems utilize 70GB DRAM and 36 CPUs. From this,
we were able to find interesting things below.
There were obviously different access pattern under idle workload and active
workload. Under the idle workload, it accessed large memory regions with low
frequency, while the active workload accessed small memory regions with high
freuqnecy.
DAMON found a 7GB memory region that showing obviously high access frequency
under the active workload. We believe this is the performance-effective
working set and need to be protected.
There was a 4KB memory region that showing highest access frequency under not
only active but also idle workloads. We think this must be a hottest code
section like thing that should never be paged out.
For this analysis, DAMON used only 0.3-1% of single CPU time. Because we used
recording-based analysis, it consumed about 3-12 MB of disk space per 20
minutes. This is only small amount of disk space, but we can further reduce
the disk usage by using non-recording-based DAMON features. I'd like to argue
that only DAMON can do such detailed analysis (finding 4KB highest region in
70GB memory) with the light overhead.
DAMON as a system optimization tool
-----------------------------------
We also found below potential performance problems on the systems and made
DAMON-based solutions.
The system doesn't want to make the workload suffer from the page reclamation
and thus it utilizes enough DRAM but no swap device. However, we found the
system is actively reclaiming file-backed pages, because the system has
intensive file IO. The file IO turned out to be not performance critical for
the workload, but the customer wanted to ensure performance critical
file-backed pages like code section to not mistakenly be evicted.
Using direct IO should or `mlock()` would be a straightforward solution, but
modifying the user space code is not easy for the customer. Alternatively, we
could use DAMON-based operation scheme[1]. By using it, we can ask DAMON to
track access frequency of each region and make
'process_madvise(MADV_WILLNEED)[2]' call for regions having specific size and
access frequency for a time interval.
We also found the system is having high number of TLB misses. We tried
'always' THP enabled policy and it greatly reduced TLB misses, but the page
reclamation also been more frequent due to the THP internal fragmentation
caused memory bloat. We could try another DAMON-based operation scheme that
applies 'MADV_HUGEPAGE' to memory regions having >=2MB size and high access
frequency, while applying 'MADV_NOHUGEPAGE' to regions having <2MB size and low
access frequency.
We do not own the systems so we only reported the analysis results and possible
optimization solutions to the customers. The customers satisfied about the
analysis results and promised to try the optimization guides.
[1] https://lore.kernel.org/linux-mm/[email protected]/
[2] https://lore.kernel.org/linux-api/[email protected]/
Comparison with Idle Page Tracking
==================================
Idle Page Tracking allows users to set and read idleness of pages using a
bitmap file which represents each page with each bit of the file. One
recommended usage of it is working set size detection. Users can do that by
1. find PFN of each page for workloads in interest,
2. set all the pages as idle by doing writes to the bitmap file,
3. wait until the workload accesses its working set, and
4. read the idleness of the pages again and count pages became not idle.
NOTE: While Idle Page Tracking is for user space users, DAMON is primarily
designed for kernel subsystems though it can easily exposed to the user space.
Hence, this section only assumes such user space use of DAMON.
For what use cases Idle Page Tracking would be better?
------------------------------------------------------
1. Flexible usecases other than hotness monitoring.
Because Idle Page Tracking allows users to control the primitive (Page
idleness) by themselves, Idle Page Tracking users can do anything they want.
Meanwhile, DAMON is primarily designed to monitor the hotness of each memory
region. For this, DAMON asks users to provide sampling interval and
aggregation interval. For the reason, there could be some use case that using
Idle Page Tracking is simpler.
2. Physical memory monitoring.
Idle Page Tracking receives PFN range as input, so natively supports physical
memory monitoring.
DAMON is designed to be extensible for multiple address spaces and use cases by
implementing and using primitives for the given use case. Therefore, by
theory, DAMON has no limitation in the type of target address space as long as
primitives for the given address space exists. However, the default primitives
introduced by this patchset supports only virtual address spaces.
Therefore, for physical memory monitoring, you should implement your own
primitives and use it, or simply use Idle Page Tracking.
Nonetheless, RFC patchsets[1] for the physical memory address space primitives
is already available. It also supports user memory same to Idle Page Tracking.
[1] https://lore.kernel.org/linux-mm/[email protected]/
For what use cases DAMON is better?
-----------------------------------
1. Hotness Monitoring.
Idle Page Tracking let users know only if a page frame is accessed or not. For
hotness check, the user should write more code and use more memory. DAMON do
that by itself.
2. Low Monitoring Overhead
DAMON receives user's monitoring request with one step and then provide the
results. So, roughly speaking, DAMON require only O(1) user/kernel context
switches.
In case of Idle Page Tracking, however, because the interface receives
contiguous page frames, the number of user/kernel context switches increases as
the monitoring target becomes complex and huge. As a result, the context
switch overhead could be not negligible.
Moreover, DAMON is born to handle with the monitoring overhead. Because the
core mechanism is pure logical, Idle Page Tracking users might be able to
implement the mechanism on thier own, but it would be time consuming and the
user/kernel context switching will still more frequent than that of DAMON.
Also, the kernel subsystems cannot use the logic in this case.
3. Page granularity working set size detection.
Until v22 of this patchset, this was categorized as the thing Idle Page
Tracking could do better, because DAMON basically maintains additional metadata
for each of the monitoring target regions. So, in the page granularity working
set size detection use case, DAMON would incur (number of monitoring target
pages * size of metadata) memory overhead. Size of the single metadata item is
about 54 bytes, so assuming 4KB pages, about 1.3% of monitoring target pages
will be additionally used.
All essential metadata for Idle Page Tracking are embedded in 'struct page' and
page table entries. Therefore, in this use case, only one counter variable for
working set size accounting is required if Idle Page Tracking is used.
There are more details to consider, but roughly speaking, this is true in most
cases.
However, the situation changed from v23. Now DAMON supports arbitrary types of
monitoring targets, which don't use the metadata. Using that, DAMON can do the
working set size detection with no additional space overhead but less
user-kernel context switch. A first draft for the implementation of monitoring
primitives for this usage is available in a DAMON development tree[1]. An RFC
patchset for it based on this patchset will also be available soon.
From v24, the arbitrary type support is dropped from this patchset because this
patchset doesn't introduce real use of the type. You can still get it from the
DAMON development tree[2], though.
[1] https://github.com/sjp38/linux/tree/damon/pgidle_hack
[2] https://github.com/sjp38/linux/tree/damon/master
4. More future usecases
While Idle Page Tracking has tight coupling with base primitives (PG_Idle and
page table Accessed bits), DAMON is designed to be extensible for many use
cases and address spaces. If you need some special address type or want to use
special h/w access check primitives, you can write your own primitives for that
and configure DAMON to use those. Therefore, if your use case could be changed
a lot in future, using DAMON could be better.
Can I use both Idle Page Tracking and DAMON?
--------------------------------------------
Yes, though using them concurrently for overlapping memory regions could result
in interference to each other. Nevertheless, such use case would be rare or
makes no sense at all. Even in the case, the noise would bot be really
significant. So, you can choose whatever you want depending on the
characteristics of your use cases.
More Information
================
We prepared a showcase web site[1] that you can get more information. There
are
- the official documentations[2],
- the heatmap format dynamic access pattern of various realistic workloads for
heap area[3], mmap()-ed area[4], and stack[5] area,
- the dynamic working set size distribution[6] and chronological working set
size changes[7], and
- the latest performance test results[8].
[1] https://damonitor.github.io/_index
[2] https://damonitor.github.io/doc/html/latest-damon
[3] https://damonitor.github.io/test/result/visual/latest/rec.heatmap.0.png.html
[4] https://damonitor.github.io/test/result/visual/latest/rec.heatmap.1.png.html
[5] https://damonitor.github.io/test/result/visual/latest/rec.heatmap.2.png.html
[6] https://damonitor.github.io/test/result/visual/latest/rec.wss_sz.png.html
[7] https://damonitor.github.io/test/result/visual/latest/rec.wss_time.png.html
[8] https://damonitor.github.io/test/result/perf/latest/html/index.html
Baseline and Complete Git Trees
===============================
The patches are based on the -mm tree. More specifically,
v5.12-rc6-mmots-2021-04-06-22-33 of https://github.com/hnaz/linux-mm. You can
also clone the complete git tree:
$ git clone git://github.com/sjp38/linux -b damon/patches/v27
The web is also available:
https://github.com/sjp38/linux/releases/tag/damon/patches/v27
Development Trees
-----------------
There are a couple of trees for entire DAMON patchset series and
features for future release.
- For latest release: https://github.com/sjp38/linux/tree/damon/master
- For next release: https://github.com/sjp38/linux/tree/damon/next
Long-term Support Trees
-----------------------
For people who want to test DAMON but using LTS kernels, there are another
couple of trees based on two latest LTS kernels respectively and containing the
'damon/master' backports.
- For v5.4.y: https://github.com/sjp38/linux/tree/damon/for-v5.4.y
- For v5.10.y: https://github.com/sjp38/linux/tree/damon/for-v5.10.y
Sequence Of Patches
===================
First three patches implement the core logics of DAMON. The 1st patch
introduces basic sampling based hotness monitoring for arbitrary types of
targets. Following two patches implement the core mechanisms for control of
overhead and accuracy, namely regions based sampling (patch 2) and adaptive
regions adjustment (patch 3).
Now the essential parts of DAMON is complete, but it cannot work unless someone
provides monitoring primitives for a specific use case. The following two
patches make it just work for virtual address spaces monitoring. The 4th patch
makes 'PG_idle' can be used by DAMON and the 5th patch implements the virtual
memory address space specific monitoring primitives using page table Accessed
bits and the 'PG_idle' page flag.
Now DAMON just works for virtual address space monitoring via the kernel space
api. To let the user space users can use DAMON, following four patches add
interfaces for them. The 6th patch adds a tracepoint for monitoring results.
The 7th patch implements a DAMON application kernel module, namely damon-dbgfs,
that simply wraps DAMON and exposes DAMON interface to the user space via the
debugfs interface. The 8th patch further exports pid of monitoring thread
(kdamond) to user space for easier cpu usage accounting, and the 9th patch
makes the debugfs interface to support multiple contexts.
Three patches for maintainability follows. The 10th patch adds documentations
for both the user space and the kernel space. The 11th patch provides unit
tests (based on the kunit) while the 12th patch adds user space tests (based on
the kselftest).
Finally, the last patch (13th) updates the MAINTAINERS file.
Patch History
=============
Changes from v26
(https://lore.kernel.org/linux-mm/[email protected]/)
- Rebase on latest -mm tree (v5.12-rc6-mmots-2021-04-06-22-33)
- Check kmalloc() failures in dbgfs init (Greg KH)
- Fix a typo: s/stollen/stolen/ (Stefan Nuernberger)
- Update document for updated user space tool path
Changes from v25
(https://lore.kernel.org/linux-mm/[email protected]/)
- Rebase on latest -mm tree (v5.12-rc4-mmots-2021-03-28-16-40)
- Remove unnecessary test code that dependent on record feature
- Handle special mappings having no corresponding 'struct page' (Guoju Fang)
Changes from v24
(https://lore.kernel.org/linux-mm/[email protected]/)
- Rebase on latest -mm tree (v5.12-rc3-mmots-2021-03-17-22-26)
- Ignore 'debugfs_create_{file|dir}()' return values (Greg KH)
- Remove 'recording' feature (Shakeel Butt)
- Remove user space tool and recording description in the documentation
Changes from v23
(https://lore.kernel.org/linux-mm/[email protected]/)
- Wordsmith commit messages (Shakeel Butt)
- Call missed mmu_notifier_test_young() (Shakeel Butt)
- Add one 'Reviewed-by' tag for PG_Idle reuse patch (Shakeel Butt)
- Rename core code to be region-neutral (Shakeel Butt)
- Add missed null check of 'damon_new_region()' return value (Coverity SAST)
- Put pids in dbgfs error cases (Shakeel Butt)
- Move arbitrary target type support out of DAMON patchset series (Shakeel Butt)
- Move user space tool patch out of DAMON patchset series
- Update evaluation result with DAMOOS-tuned prcl schemes
Changes from v22
(https://lore.kernel.org/linux-mm/[email protected]/)
- Support arbitrary targets; now DAMON incurs only zero space overhead for page
granularity idleness monitoring
- Reorder patches for easier review (Shakeel Butt)
- Introduce arbitrary targets with sampling first, then the overhead-accuracy
control logic
- Introduce data structure manipulation functions when it really used.
- Call callbacks explicitly, without macro (Shakeel Butt)
- Rename DAMON_PRIMITIVES to DAMON_VADDR (Shakeel Butt)
- Remove 'page_idle_lock' patch (Shakeel Butt)
- Drop pidfd support in debugfs (Shakeel Butt)
Changes from v21
(https://lore.kernel.org/linux-doc/[email protected]/)
- Fix build warnings and errors (kernel test robot)
- Fix a memory leak (kmemleak)
- Respect KUNIT_ALL_TESTS
- Rebase on v5.9
- Update the evaluation results
Changes from v20
(https://lore.kernel.org/linux-mm/[email protected]/)
- s/snprintf()/scnprintf() (Marco Elver)
- Support multiple contexts for user space users (Shakeel Butt)
- Export pid of monitoring thread to user space (Shakeel Butt)
- Let coexistable with Idle Page Tracking
- Place three parts of DAMON (core, primitives, and dbgfs) in different files
Changes from v19
(https://lore.kernel.org/linux-mm/[email protected]/)
- Place 'CREATE_TRACE_POINTS' after '#include' statements (Steven Rostedt)
- Support large record file (Alkaid)
- Place 'put_pid()' of virtual monitoring targets in 'cleanup' callback
- Avoid conflict between concurrent DAMON users
- Update evaluation result document
Changes from v18
(https://lore.kernel.org/linux-mm/[email protected]/)
- Drop loadable module support (Mike Rapoport)
- Select PAGE_EXTENSION if !64BIT for 'set_page_young()'
- Take care of the MMU notification subscribers (Shakeel Butt)
- Substitute 'struct damon_task' with 'struct damon_target' for better abstract
- Use 'struct pid' instead of 'pid_t' as the target (Shakeel Butt)
- Support pidfd from the debugfs interface (Shakeel Butt)
- Fix typos (Greg Thelen)
- Properly isolate DAMON from other pmd/pte Accessed bit users (Greg Thelen)
- Rebase on v5.8
Please refer to the v18 patchset to get older history.
SeongJae Park (13):
mm: Introduce Data Access MONitor (DAMON)
mm/damon/core: Implement region-based sampling
mm/damon: Adaptively adjust regions
mm/idle_page_tracking: Make PG_idle reusable
mm/damon: Implement primitives for the virtual memory address spaces
mm/damon: Add a tracepoint
mm/damon: Implement a debugfs-based user space interface
mm/damon/dbgfs: Export kdamond pid to the user space
mm/damon/dbgfs: Support multiple contexts
Documentation: Add documents for DAMON
mm/damon: Add kunit tests
mm/damon: Add user space selftests
MAINTAINERS: Update for DAMON
Documentation/admin-guide/mm/damon/guide.rst | 158 ++++
Documentation/admin-guide/mm/damon/index.rst | 15 +
Documentation/admin-guide/mm/damon/plans.rst | 29 +
Documentation/admin-guide/mm/damon/start.rst | 114 +++
Documentation/admin-guide/mm/damon/usage.rst | 112 +++
Documentation/admin-guide/mm/index.rst | 1 +
Documentation/vm/damon/api.rst | 20 +
Documentation/vm/damon/design.rst | 166 ++++
Documentation/vm/damon/eval.rst | 232 ++++++
Documentation/vm/damon/faq.rst | 58 ++
Documentation/vm/damon/index.rst | 31 +
Documentation/vm/index.rst | 1 +
MAINTAINERS | 12 +
include/linux/damon.h | 265 +++++++
include/linux/page-flags.h | 4 +-
include/linux/page_ext.h | 2 +-
include/linux/page_idle.h | 6 +-
include/trace/events/damon.h | 43 ++
include/trace/events/mmflags.h | 2 +-
mm/Kconfig | 11 +
mm/Makefile | 1 +
mm/damon/Kconfig | 69 ++
mm/damon/Makefile | 5 +
mm/damon/core-test.h | 253 ++++++
mm/damon/core.c | 718 ++++++++++++++++++
mm/damon/dbgfs-test.h | 126 +++
mm/damon/dbgfs.c | 617 +++++++++++++++
mm/damon/vaddr-test.h | 328 ++++++++
mm/damon/vaddr.c | 623 +++++++++++++++
mm/page_ext.c | 12 +-
mm/page_idle.c | 10 -
tools/testing/selftests/damon/Makefile | 7 +
.../selftests/damon/_chk_dependency.sh | 28 +
.../testing/selftests/damon/debugfs_attrs.sh | 98 +++
34 files changed, 4159 insertions(+), 18 deletions(-)
create mode 100644 Documentation/admin-guide/mm/damon/guide.rst
create mode 100644 Documentation/admin-guide/mm/damon/index.rst
create mode 100644 Documentation/admin-guide/mm/damon/plans.rst
create mode 100644 Documentation/admin-guide/mm/damon/start.rst
create mode 100644 Documentation/admin-guide/mm/damon/usage.rst
create mode 100644 Documentation/vm/damon/api.rst
create mode 100644 Documentation/vm/damon/design.rst
create mode 100644 Documentation/vm/damon/eval.rst
create mode 100644 Documentation/vm/damon/faq.rst
create mode 100644 Documentation/vm/damon/index.rst
create mode 100644 include/linux/damon.h
create mode 100644 include/trace/events/damon.h
create mode 100644 mm/damon/Kconfig
create mode 100644 mm/damon/Makefile
create mode 100644 mm/damon/core-test.h
create mode 100644 mm/damon/core.c
create mode 100644 mm/damon/dbgfs-test.h
create mode 100644 mm/damon/dbgfs.c
create mode 100644 mm/damon/vaddr-test.h
create mode 100644 mm/damon/vaddr.c
create mode 100644 tools/testing/selftests/damon/Makefile
create mode 100644 tools/testing/selftests/damon/_chk_dependency.sh
create mode 100755 tools/testing/selftests/damon/debugfs_attrs.sh
--
2.17.1
From: SeongJae Park <[email protected]>
In some use cases, users would want to run multiple monitoring context.
For example, if a user wants a high precision monitoring and dedicating
multiple CPUs for the job is ok, because DAMON creates one monitoring
thread per one context, the user can split the monitoring target regions
into multiple small regions and create one context for each region. Or,
someone might want to simultaneously monitor different address spaces,
e.g., both virtual address space and physical address space.
The DAMON's API allows such usage, but 'damon-dbgfs' does not.
Therefore, only kernel space DAMON users can do multiple contexts
monitoring.
This commit allows the user space DAMON users to use multiple contexts
monitoring by introducing two new 'damon-dbgfs' debugfs files,
'mk_context' and 'rm_context'. Users can create a new monitoring
context by writing the desired name of the new context to 'mk_context'.
Then, a new directory with the name and having the files for setting of
the context ('attrs', 'target_ids' and 'record') will be created under
the debugfs directory. Writing the name of the context to remove to
'rm_context' will remove the related context and directory.
Signed-off-by: SeongJae Park <[email protected]>
---
mm/damon/dbgfs.c | 203 ++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 201 insertions(+), 2 deletions(-)
diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
index b20c1e7742ce..66ac7e18b1df 100644
--- a/mm/damon/dbgfs.c
+++ b/mm/damon/dbgfs.c
@@ -18,6 +18,7 @@
static struct damon_ctx **dbgfs_ctxs;
static int dbgfs_nr_ctxs;
static struct dentry **dbgfs_dirs;
+static DEFINE_MUTEX(damon_dbgfs_lock);
/*
* Returns non-empty string on success, negarive error code otherwise.
@@ -316,6 +317,192 @@ static struct damon_ctx *dbgfs_new_ctx(void)
return ctx;
}
+static void dbgfs_destroy_ctx(struct damon_ctx *ctx)
+{
+ damon_destroy_ctx(ctx);
+}
+
+/*
+ * Make a context of @name and create a debugfs directory for it.
+ *
+ * This function should be called while holding damon_dbgfs_lock.
+ *
+ * Returns 0 on success, negative error code otherwise.
+ */
+static int dbgfs_mk_context(char *name)
+{
+ struct dentry *root, **new_dirs, *new_dir;
+ struct damon_ctx **new_ctxs, *new_ctx;
+ int err;
+
+ if (damon_nr_running_ctxs())
+ return -EBUSY;
+
+ new_ctxs = krealloc(dbgfs_ctxs, sizeof(*dbgfs_ctxs) *
+ (dbgfs_nr_ctxs + 1), GFP_KERNEL);
+ if (!new_ctxs)
+ return -ENOMEM;
+
+ new_dirs = krealloc(dbgfs_dirs, sizeof(*dbgfs_dirs) *
+ (dbgfs_nr_ctxs + 1), GFP_KERNEL);
+ if (!new_dirs) {
+ kfree(new_ctxs);
+ return -ENOMEM;
+ }
+
+ dbgfs_ctxs = new_ctxs;
+ dbgfs_dirs = new_dirs;
+
+ root = dbgfs_dirs[0];
+ if (!root)
+ return -ENOENT;
+
+ new_dir = debugfs_create_dir(name, root);
+ dbgfs_dirs[dbgfs_nr_ctxs] = new_dir;
+
+ new_ctx = dbgfs_new_ctx();
+ if (!new_ctx) {
+ debugfs_remove(new_dir);
+ dbgfs_dirs[dbgfs_nr_ctxs] = NULL;
+ return -ENOMEM;
+ }
+ dbgfs_ctxs[dbgfs_nr_ctxs] = new_ctx;
+
+ err = dbgfs_fill_ctx_dir(dbgfs_dirs[dbgfs_nr_ctxs],
+ dbgfs_ctxs[dbgfs_nr_ctxs]);
+ if (err)
+ return err;
+
+ dbgfs_nr_ctxs++;
+ return 0;
+}
+
+static ssize_t dbgfs_mk_context_write(struct file *file,
+ const char __user *buf, size_t count, loff_t *ppos)
+{
+ char *kbuf;
+ char *ctx_name;
+ ssize_t ret = count;
+ int err;
+
+ kbuf = user_input_str(buf, count, ppos);
+ if (IS_ERR(kbuf))
+ return PTR_ERR(kbuf);
+ ctx_name = kmalloc(count + 1, GFP_KERNEL);
+ if (!ctx_name) {
+ kfree(kbuf);
+ return -ENOMEM;
+ }
+
+ /* Trim white space */
+ if (sscanf(kbuf, "%s", ctx_name) != 1) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ mutex_lock(&damon_dbgfs_lock);
+ err = dbgfs_mk_context(ctx_name);
+ if (err)
+ ret = err;
+ mutex_unlock(&damon_dbgfs_lock);
+
+out:
+ kfree(kbuf);
+ kfree(ctx_name);
+ return ret;
+}
+
+/*
+ * Remove a context of @name and its debugfs directory.
+ *
+ * This function should be called while holding damon_dbgfs_lock.
+ *
+ * Return 0 on success, negative error code otherwise.
+ */
+static int dbgfs_rm_context(char *name)
+{
+ struct dentry *root, *dir, **new_dirs;
+ struct damon_ctx **new_ctxs;
+ int i, j;
+
+ if (damon_nr_running_ctxs())
+ return -EBUSY;
+
+ root = dbgfs_dirs[0];
+ if (!root)
+ return -ENOENT;
+
+ dir = debugfs_lookup(name, root);
+ if (!dir)
+ return -ENOENT;
+
+ new_dirs = kmalloc_array(dbgfs_nr_ctxs - 1, sizeof(*dbgfs_dirs),
+ GFP_KERNEL);
+ if (!new_dirs)
+ return -ENOMEM;
+
+ new_ctxs = kmalloc_array(dbgfs_nr_ctxs - 1, sizeof(*dbgfs_ctxs),
+ GFP_KERNEL);
+ if (!new_ctxs) {
+ kfree(new_dirs);
+ return -ENOMEM;
+ }
+
+ for (i = 0, j = 0; i < dbgfs_nr_ctxs; i++) {
+ if (dbgfs_dirs[i] == dir) {
+ debugfs_remove(dbgfs_dirs[i]);
+ dbgfs_destroy_ctx(dbgfs_ctxs[i]);
+ continue;
+ }
+ new_dirs[j] = dbgfs_dirs[i];
+ new_ctxs[j++] = dbgfs_ctxs[i];
+ }
+
+ kfree(dbgfs_dirs);
+ kfree(dbgfs_ctxs);
+
+ dbgfs_dirs = new_dirs;
+ dbgfs_ctxs = new_ctxs;
+ dbgfs_nr_ctxs--;
+
+ return 0;
+}
+
+static ssize_t dbgfs_rm_context_write(struct file *file,
+ const char __user *buf, size_t count, loff_t *ppos)
+{
+ char *kbuf;
+ ssize_t ret = count;
+ int err;
+ char *ctx_name;
+
+ kbuf = user_input_str(buf, count, ppos);
+ if (IS_ERR(kbuf))
+ return PTR_ERR(kbuf);
+ ctx_name = kmalloc(count + 1, GFP_KERNEL);
+ if (!ctx_name) {
+ kfree(kbuf);
+ return -ENOMEM;
+ }
+
+ /* Trim white space */
+ if (sscanf(kbuf, "%s", ctx_name) != 1) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ mutex_lock(&damon_dbgfs_lock);
+ err = dbgfs_rm_context(ctx_name);
+ if (err)
+ ret = err;
+ mutex_unlock(&damon_dbgfs_lock);
+
+out:
+ kfree(kbuf);
+ kfree(ctx_name);
+ return ret;
+}
+
static ssize_t dbgfs_monitor_on_read(struct file *file,
char __user *buf, size_t count, loff_t *ppos)
{
@@ -358,6 +545,16 @@ static ssize_t dbgfs_monitor_on_write(struct file *file,
return ret;
}
+static const struct file_operations mk_contexts_fops = {
+ .owner = THIS_MODULE,
+ .write = dbgfs_mk_context_write,
+};
+
+static const struct file_operations rm_contexts_fops = {
+ .owner = THIS_MODULE,
+ .write = dbgfs_rm_context_write,
+};
+
static const struct file_operations monitor_on_fops = {
.owner = THIS_MODULE,
.read = dbgfs_monitor_on_read,
@@ -367,8 +564,10 @@ static const struct file_operations monitor_on_fops = {
static int __init __damon_dbgfs_init(void)
{
struct dentry *dbgfs_root;
- const char * const file_names[] = {"monitor_on"};
- const struct file_operations *fops[] = {&monitor_on_fops};
+ const char * const file_names[] = {"mk_contexts", "rm_contexts",
+ "monitor_on"};
+ const struct file_operations *fops[] = {&mk_contexts_fops,
+ &rm_contexts_fops, &monitor_on_fops};
int i;
dbgfs_root = debugfs_create_dir("damon", NULL);
--
2.17.1
From: SeongJae Park <[email protected]>
For CPU usage accounting, knowing pid of the monitoring thread could be
helpful. For example, users could use cpuaccount cgroups with the pid.
This commit therefore exports the pid of currently running monitoring
thread to the user space via 'kdamond_pid' file in the debugfs
directory.
Signed-off-by: SeongJae Park <[email protected]>
---
mm/damon/dbgfs.c | 38 ++++++++++++++++++++++++++++++++++++--
1 file changed, 36 insertions(+), 2 deletions(-)
diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
index 9af844faffd4..b20c1e7742ce 100644
--- a/mm/damon/dbgfs.c
+++ b/mm/damon/dbgfs.c
@@ -237,6 +237,32 @@ static ssize_t dbgfs_target_ids_write(struct file *file,
return ret;
}
+static ssize_t dbgfs_kdamond_pid_read(struct file *file,
+ char __user *buf, size_t count, loff_t *ppos)
+{
+ struct damon_ctx *ctx = file->private_data;
+ char *kbuf;
+ ssize_t len;
+
+ kbuf = kmalloc(count, GFP_KERNEL);
+ if (!kbuf)
+ return -ENOMEM;
+
+ mutex_lock(&ctx->kdamond_lock);
+ if (ctx->kdamond)
+ len = scnprintf(kbuf, count, "%d\n", ctx->kdamond->pid);
+ else
+ len = scnprintf(kbuf, count, "none\n");
+ mutex_unlock(&ctx->kdamond_lock);
+ if (!len)
+ goto out;
+ len = simple_read_from_buffer(buf, count, ppos, kbuf, len);
+
+out:
+ kfree(kbuf);
+ return len;
+}
+
static int damon_dbgfs_open(struct inode *inode, struct file *file)
{
file->private_data = inode->i_private;
@@ -258,10 +284,18 @@ static const struct file_operations target_ids_fops = {
.write = dbgfs_target_ids_write,
};
+static const struct file_operations kdamond_pid_fops = {
+ .owner = THIS_MODULE,
+ .open = damon_dbgfs_open,
+ .read = dbgfs_kdamond_pid_read,
+};
+
static int dbgfs_fill_ctx_dir(struct dentry *dir, struct damon_ctx *ctx)
{
- const char * const file_names[] = {"attrs", "target_ids"};
- const struct file_operations *fops[] = {&attrs_fops, &target_ids_fops};
+ const char * const file_names[] = {"attrs", "target_ids",
+ "kdamond_pid"};
+ const struct file_operations *fops[] = {&attrs_fops, &target_ids_fops,
+ &kdamond_pid_fops};
int i;
for (i = 0; i < ARRAY_SIZE(file_names); i++)
--
2.17.1
From: SeongJae Park <[email protected]>
This commit adds kunit based unit tests for the core and the virtual
address spaces monitoring primitives of DAMON.
Signed-off-by: SeongJae Park <[email protected]>
Reviewed-by: Brendan Higgins <[email protected]>
---
mm/damon/Kconfig | 36 +++++
mm/damon/core-test.h | 253 ++++++++++++++++++++++++++++++++
mm/damon/core.c | 7 +
mm/damon/dbgfs-test.h | 126 ++++++++++++++++
mm/damon/dbgfs.c | 2 +
mm/damon/vaddr-test.h | 328 ++++++++++++++++++++++++++++++++++++++++++
mm/damon/vaddr.c | 7 +
7 files changed, 759 insertions(+)
create mode 100644 mm/damon/core-test.h
create mode 100644 mm/damon/dbgfs-test.h
create mode 100644 mm/damon/vaddr-test.h
diff --git a/mm/damon/Kconfig b/mm/damon/Kconfig
index 72f1683ba0ee..455995152697 100644
--- a/mm/damon/Kconfig
+++ b/mm/damon/Kconfig
@@ -12,6 +12,18 @@ config DAMON
See https://damonitor.github.io/doc/html/latest-damon/index.html for
more information.
+config DAMON_KUNIT_TEST
+ bool "Test for damon" if !KUNIT_ALL_TESTS
+ depends on DAMON && KUNIT=y
+ default KUNIT_ALL_TESTS
+ help
+ This builds the DAMON Kunit test suite.
+
+ For more information on KUnit and unit tests in general, please refer
+ to the KUnit documentation.
+
+ If unsure, say N.
+
config DAMON_VADDR
bool "Data access monitoring primitives for virtual address spaces"
depends on DAMON && MMU
@@ -21,6 +33,18 @@ config DAMON_VADDR
This builds the default data access monitoring primitives for DAMON
that works for virtual address spaces.
+config DAMON_VADDR_KUNIT_TEST
+ bool "Test for DAMON primitives" if !KUNIT_ALL_TESTS
+ depends on DAMON_VADDR && KUNIT=y
+ default KUNIT_ALL_TESTS
+ help
+ This builds the DAMON virtual addresses primitives Kunit test suite.
+
+ For more information on KUnit and unit tests in general, please refer
+ to the KUnit documentation.
+
+ If unsure, say N.
+
config DAMON_DBGFS
bool "DAMON debugfs interface"
depends on DAMON_VADDR && DEBUG_FS
@@ -30,4 +54,16 @@ config DAMON_DBGFS
If unsure, say N.
+config DAMON_DBGFS_KUNIT_TEST
+ bool "Test for damon debugfs interface" if !KUNIT_ALL_TESTS
+ depends on DAMON_DBGFS && KUNIT=y
+ default KUNIT_ALL_TESTS
+ help
+ This builds the DAMON debugfs interface Kunit test suite.
+
+ For more information on KUnit and unit tests in general, please refer
+ to the KUnit documentation.
+
+ If unsure, say N.
+
endmenu
diff --git a/mm/damon/core-test.h b/mm/damon/core-test.h
new file mode 100644
index 000000000000..b815dfbfb5fd
--- /dev/null
+++ b/mm/damon/core-test.h
@@ -0,0 +1,253 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Data Access Monitor Unit Tests
+ *
+ * Copyright 2019 Amazon.com, Inc. or its affiliates. All rights reserved.
+ *
+ * Author: SeongJae Park <[email protected]>
+ */
+
+#ifdef CONFIG_DAMON_KUNIT_TEST
+
+#ifndef _DAMON_CORE_TEST_H
+#define _DAMON_CORE_TEST_H
+
+#include <kunit/test.h>
+
+static void damon_test_regions(struct kunit *test)
+{
+ struct damon_region *r;
+ struct damon_target *t;
+
+ r = damon_new_region(1, 2);
+ KUNIT_EXPECT_EQ(test, 1ul, r->ar.start);
+ KUNIT_EXPECT_EQ(test, 2ul, r->ar.end);
+ KUNIT_EXPECT_EQ(test, 0u, r->nr_accesses);
+
+ t = damon_new_target(42);
+ KUNIT_EXPECT_EQ(test, 0u, damon_nr_regions(t));
+
+ damon_add_region(r, t);
+ KUNIT_EXPECT_EQ(test, 1u, damon_nr_regions(t));
+
+ damon_del_region(r);
+ KUNIT_EXPECT_EQ(test, 0u, damon_nr_regions(t));
+
+ damon_free_target(t);
+}
+
+static unsigned int nr_damon_targets(struct damon_ctx *ctx)
+{
+ struct damon_target *t;
+ unsigned int nr_targets = 0;
+
+ damon_for_each_target(t, ctx)
+ nr_targets++;
+
+ return nr_targets;
+}
+
+static void damon_test_target(struct kunit *test)
+{
+ struct damon_ctx *c = damon_new_ctx();
+ struct damon_target *t;
+
+ t = damon_new_target(42);
+ KUNIT_EXPECT_EQ(test, 42ul, t->id);
+ KUNIT_EXPECT_EQ(test, 0u, nr_damon_targets(c));
+
+ damon_add_target(c, t);
+ KUNIT_EXPECT_EQ(test, 1u, nr_damon_targets(c));
+
+ damon_destroy_target(t);
+ KUNIT_EXPECT_EQ(test, 0u, nr_damon_targets(c));
+
+ damon_destroy_ctx(c);
+}
+
+/*
+ * Test kdamond_reset_aggregated()
+ *
+ * DAMON checks access to each region and aggregates this information as the
+ * access frequency of each region. In detail, it increases '->nr_accesses' of
+ * regions that an access has confirmed. 'kdamond_reset_aggregated()' flushes
+ * the aggregated information ('->nr_accesses' of each regions) to the result
+ * buffer. As a result of the flushing, the '->nr_accesses' of regions are
+ * initialized to zero.
+ */
+static void damon_test_aggregate(struct kunit *test)
+{
+ struct damon_ctx *ctx = damon_new_ctx();
+ unsigned long target_ids[] = {1, 2, 3};
+ unsigned long saddr[][3] = {{10, 20, 30}, {5, 42, 49}, {13, 33, 55} };
+ unsigned long eaddr[][3] = {{15, 27, 40}, {31, 45, 55}, {23, 44, 66} };
+ unsigned long accesses[][3] = {{42, 95, 84}, {10, 20, 30}, {0, 1, 2} };
+ struct damon_target *t;
+ struct damon_region *r;
+ int it, ir;
+
+ damon_set_targets(ctx, target_ids, 3);
+
+ it = 0;
+ damon_for_each_target(t, ctx) {
+ for (ir = 0; ir < 3; ir++) {
+ r = damon_new_region(saddr[it][ir], eaddr[it][ir]);
+ r->nr_accesses = accesses[it][ir];
+ damon_add_region(r, t);
+ }
+ it++;
+ }
+ kdamond_reset_aggregated(ctx);
+ it = 0;
+ damon_for_each_target(t, ctx) {
+ ir = 0;
+ /* '->nr_accesses' should be zeroed */
+ damon_for_each_region(r, t) {
+ KUNIT_EXPECT_EQ(test, 0u, r->nr_accesses);
+ ir++;
+ }
+ /* regions should be preserved */
+ KUNIT_EXPECT_EQ(test, 3, ir);
+ it++;
+ }
+ /* targets also should be preserved */
+ KUNIT_EXPECT_EQ(test, 3, it);
+
+ damon_destroy_ctx(ctx);
+}
+
+static void damon_test_split_at(struct kunit *test)
+{
+ struct damon_ctx *c = damon_new_ctx();
+ struct damon_target *t;
+ struct damon_region *r;
+
+ t = damon_new_target(42);
+ r = damon_new_region(0, 100);
+ damon_add_region(r, t);
+ damon_split_region_at(c, r, 25);
+ KUNIT_EXPECT_EQ(test, r->ar.start, 0ul);
+ KUNIT_EXPECT_EQ(test, r->ar.end, 25ul);
+
+ r = damon_next_region(r);
+ KUNIT_EXPECT_EQ(test, r->ar.start, 25ul);
+ KUNIT_EXPECT_EQ(test, r->ar.end, 100ul);
+
+ damon_free_target(t);
+ damon_destroy_ctx(c);
+}
+
+static void damon_test_merge_two(struct kunit *test)
+{
+ struct damon_target *t;
+ struct damon_region *r, *r2, *r3;
+ int i;
+
+ t = damon_new_target(42);
+ r = damon_new_region(0, 100);
+ r->nr_accesses = 10;
+ damon_add_region(r, t);
+ r2 = damon_new_region(100, 300);
+ r2->nr_accesses = 20;
+ damon_add_region(r2, t);
+
+ damon_merge_two_regions(r, r2);
+ KUNIT_EXPECT_EQ(test, r->ar.start, 0ul);
+ KUNIT_EXPECT_EQ(test, r->ar.end, 300ul);
+ KUNIT_EXPECT_EQ(test, r->nr_accesses, 16u);
+
+ i = 0;
+ damon_for_each_region(r3, t) {
+ KUNIT_EXPECT_PTR_EQ(test, r, r3);
+ i++;
+ }
+ KUNIT_EXPECT_EQ(test, i, 1);
+
+ damon_free_target(t);
+}
+
+static struct damon_region *__nth_region_of(struct damon_target *t, int idx)
+{
+ struct damon_region *r;
+ unsigned int i = 0;
+
+ damon_for_each_region(r, t) {
+ if (i++ == idx)
+ return r;
+ }
+
+ return NULL;
+}
+
+static void damon_test_merge_regions_of(struct kunit *test)
+{
+ struct damon_target *t;
+ struct damon_region *r;
+ unsigned long sa[] = {0, 100, 114, 122, 130, 156, 170, 184};
+ unsigned long ea[] = {100, 112, 122, 130, 156, 170, 184, 230};
+ unsigned int nrs[] = {0, 0, 10, 10, 20, 30, 1, 2};
+
+ unsigned long saddrs[] = {0, 114, 130, 156, 170};
+ unsigned long eaddrs[] = {112, 130, 156, 170, 230};
+ int i;
+
+ t = damon_new_target(42);
+ for (i = 0; i < ARRAY_SIZE(sa); i++) {
+ r = damon_new_region(sa[i], ea[i]);
+ r->nr_accesses = nrs[i];
+ damon_add_region(r, t);
+ }
+
+ damon_merge_regions_of(t, 9, 9999);
+ /* 0-112, 114-130, 130-156, 156-170 */
+ KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 5u);
+ for (i = 0; i < 5; i++) {
+ r = __nth_region_of(t, i);
+ KUNIT_EXPECT_EQ(test, r->ar.start, saddrs[i]);
+ KUNIT_EXPECT_EQ(test, r->ar.end, eaddrs[i]);
+ }
+ damon_free_target(t);
+}
+
+static void damon_test_split_regions_of(struct kunit *test)
+{
+ struct damon_ctx *c = damon_new_ctx();
+ struct damon_target *t;
+ struct damon_region *r;
+
+ t = damon_new_target(42);
+ r = damon_new_region(0, 22);
+ damon_add_region(r, t);
+ damon_split_regions_of(c, t, 2);
+ KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 2u);
+ damon_free_target(t);
+
+ t = damon_new_target(42);
+ r = damon_new_region(0, 220);
+ damon_add_region(r, t);
+ damon_split_regions_of(c, t, 4);
+ KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 4u);
+ damon_free_target(t);
+ damon_destroy_ctx(c);
+}
+
+static struct kunit_case damon_test_cases[] = {
+ KUNIT_CASE(damon_test_target),
+ KUNIT_CASE(damon_test_regions),
+ KUNIT_CASE(damon_test_aggregate),
+ KUNIT_CASE(damon_test_split_at),
+ KUNIT_CASE(damon_test_merge_two),
+ KUNIT_CASE(damon_test_merge_regions_of),
+ KUNIT_CASE(damon_test_split_regions_of),
+ {},
+};
+
+static struct kunit_suite damon_test_suite = {
+ .name = "damon",
+ .test_cases = damon_test_cases,
+};
+kunit_test_suite(damon_test_suite);
+
+#endif /* _DAMON_CORE_TEST_H */
+
+#endif /* CONFIG_DAMON_KUNIT_TEST */
diff --git a/mm/damon/core.c b/mm/damon/core.c
index cad2b4cee39d..6bfb5d7d9142 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -16,6 +16,11 @@
#define CREATE_TRACE_POINTS
#include <trace/events/damon.h>
+#ifdef CONFIG_DAMON_KUNIT_TEST
+#undef DAMON_MIN_REGION
+#define DAMON_MIN_REGION 1
+#endif
+
/* Get a random number in [l, r) */
#define damon_rand(l, r) (l + prandom_u32_max(r - l))
@@ -709,3 +714,5 @@ static int kdamond_fn(void *data)
do_exit(0);
}
+
+#include "core-test.h"
diff --git a/mm/damon/dbgfs-test.h b/mm/damon/dbgfs-test.h
new file mode 100644
index 000000000000..930e83bceef0
--- /dev/null
+++ b/mm/damon/dbgfs-test.h
@@ -0,0 +1,126 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * DAMON Debugfs Interface Unit Tests
+ *
+ * Author: SeongJae Park <[email protected]>
+ */
+
+#ifdef CONFIG_DAMON_DBGFS_KUNIT_TEST
+
+#ifndef _DAMON_DBGFS_TEST_H
+#define _DAMON_DBGFS_TEST_H
+
+#include <kunit/test.h>
+
+static void damon_dbgfs_test_str_to_target_ids(struct kunit *test)
+{
+ char *question;
+ unsigned long *answers;
+ unsigned long expected[] = {12, 35, 46};
+ ssize_t nr_integers = 0, i;
+
+ question = "123";
+ answers = str_to_target_ids(question, strnlen(question, 128),
+ &nr_integers);
+ KUNIT_EXPECT_EQ(test, (ssize_t)1, nr_integers);
+ KUNIT_EXPECT_EQ(test, 123ul, answers[0]);
+ kfree(answers);
+
+ question = "123abc";
+ answers = str_to_target_ids(question, strnlen(question, 128),
+ &nr_integers);
+ KUNIT_EXPECT_EQ(test, (ssize_t)1, nr_integers);
+ KUNIT_EXPECT_EQ(test, 123ul, answers[0]);
+ kfree(answers);
+
+ question = "a123";
+ answers = str_to_target_ids(question, strnlen(question, 128),
+ &nr_integers);
+ KUNIT_EXPECT_EQ(test, (ssize_t)0, nr_integers);
+ kfree(answers);
+
+ question = "12 35";
+ answers = str_to_target_ids(question, strnlen(question, 128),
+ &nr_integers);
+ KUNIT_EXPECT_EQ(test, (ssize_t)2, nr_integers);
+ for (i = 0; i < nr_integers; i++)
+ KUNIT_EXPECT_EQ(test, expected[i], answers[i]);
+ kfree(answers);
+
+ question = "12 35 46";
+ answers = str_to_target_ids(question, strnlen(question, 128),
+ &nr_integers);
+ KUNIT_EXPECT_EQ(test, (ssize_t)3, nr_integers);
+ for (i = 0; i < nr_integers; i++)
+ KUNIT_EXPECT_EQ(test, expected[i], answers[i]);
+ kfree(answers);
+
+ question = "12 35 abc 46";
+ answers = str_to_target_ids(question, strnlen(question, 128),
+ &nr_integers);
+ KUNIT_EXPECT_EQ(test, (ssize_t)2, nr_integers);
+ for (i = 0; i < 2; i++)
+ KUNIT_EXPECT_EQ(test, expected[i], answers[i]);
+ kfree(answers);
+
+ question = "";
+ answers = str_to_target_ids(question, strnlen(question, 128),
+ &nr_integers);
+ KUNIT_EXPECT_EQ(test, (ssize_t)0, nr_integers);
+ kfree(answers);
+
+ question = "\n";
+ answers = str_to_target_ids(question, strnlen(question, 128),
+ &nr_integers);
+ KUNIT_EXPECT_EQ(test, (ssize_t)0, nr_integers);
+ kfree(answers);
+}
+
+static void damon_dbgfs_test_set_targets(struct kunit *test)
+{
+ struct damon_ctx *ctx = dbgfs_new_ctx();
+ unsigned long ids[] = {1, 2, 3};
+ char buf[64];
+
+ /* Make DAMON consider target id as plain number */
+ ctx->primitive.target_valid = NULL;
+ ctx->primitive.cleanup = NULL;
+
+ damon_set_targets(ctx, ids, 3);
+ sprint_target_ids(ctx, buf, 64);
+ KUNIT_EXPECT_STREQ(test, (char *)buf, "1 2 3\n");
+
+ damon_set_targets(ctx, NULL, 0);
+ sprint_target_ids(ctx, buf, 64);
+ KUNIT_EXPECT_STREQ(test, (char *)buf, "\n");
+
+ damon_set_targets(ctx, (unsigned long []){1, 2}, 2);
+ sprint_target_ids(ctx, buf, 64);
+ KUNIT_EXPECT_STREQ(test, (char *)buf, "1 2\n");
+
+ damon_set_targets(ctx, (unsigned long []){2}, 1);
+ sprint_target_ids(ctx, buf, 64);
+ KUNIT_EXPECT_STREQ(test, (char *)buf, "2\n");
+
+ damon_set_targets(ctx, NULL, 0);
+ sprint_target_ids(ctx, buf, 64);
+ KUNIT_EXPECT_STREQ(test, (char *)buf, "\n");
+
+ dbgfs_destroy_ctx(ctx);
+}
+
+static struct kunit_case damon_test_cases[] = {
+ KUNIT_CASE(damon_dbgfs_test_str_to_target_ids),
+ KUNIT_CASE(damon_dbgfs_test_set_targets),
+ {},
+};
+
+static struct kunit_suite damon_test_suite = {
+ .name = "damon-dbgfs",
+ .test_cases = damon_test_cases,
+};
+kunit_test_suite(damon_test_suite);
+
+#endif /* _DAMON_TEST_H */
+
+#endif /* CONFIG_DAMON_KUNIT_TEST */
diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
index 66ac7e18b1df..51a300d3de1f 100644
--- a/mm/damon/dbgfs.c
+++ b/mm/damon/dbgfs.c
@@ -613,3 +613,5 @@ static int __init damon_dbgfs_init(void)
}
module_init(damon_dbgfs_init);
+
+#include "dbgfs-test.h"
diff --git a/mm/damon/vaddr-test.h b/mm/damon/vaddr-test.h
new file mode 100644
index 000000000000..c9394e1d21d3
--- /dev/null
+++ b/mm/damon/vaddr-test.h
@@ -0,0 +1,328 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Data Access Monitor Unit Tests
+ *
+ * Copyright 2019 Amazon.com, Inc. or its affiliates. All rights reserved.
+ *
+ * Author: SeongJae Park <[email protected]>
+ */
+
+#ifdef CONFIG_DAMON_VADDR_KUNIT_TEST
+
+#ifndef _DAMON_VADDR_TEST_H
+#define _DAMON_VADDR_TEST_H
+
+#include <kunit/test.h>
+
+static void __link_vmas(struct vm_area_struct *vmas, ssize_t nr_vmas)
+{
+ int i, j;
+ unsigned long largest_gap, gap;
+
+ if (!nr_vmas)
+ return;
+
+ for (i = 0; i < nr_vmas - 1; i++) {
+ vmas[i].vm_next = &vmas[i + 1];
+
+ vmas[i].vm_rb.rb_left = NULL;
+ vmas[i].vm_rb.rb_right = &vmas[i + 1].vm_rb;
+
+ largest_gap = 0;
+ for (j = i; j < nr_vmas; j++) {
+ if (j == 0)
+ continue;
+ gap = vmas[j].vm_start - vmas[j - 1].vm_end;
+ if (gap > largest_gap)
+ largest_gap = gap;
+ }
+ vmas[i].rb_subtree_gap = largest_gap;
+ }
+ vmas[i].vm_next = NULL;
+ vmas[i].vm_rb.rb_right = NULL;
+ vmas[i].rb_subtree_gap = 0;
+}
+
+/*
+ * Test __damon_va_three_regions() function
+ *
+ * In case of virtual memory address spaces monitoring, DAMON converts the
+ * complex and dynamic memory mappings of each target task to three
+ * discontiguous regions which cover every mapped areas. However, the three
+ * regions should not include the two biggest unmapped areas in the original
+ * mapping, because the two biggest areas are normally the areas between 1)
+ * heap and the mmap()-ed regions, and 2) the mmap()-ed regions and stack.
+ * Because these two unmapped areas are very huge but obviously never accessed,
+ * covering the region is just a waste.
+ *
+ * '__damon_va_three_regions() receives an address space of a process. It
+ * first identifies the start of mappings, end of mappings, and the two biggest
+ * unmapped areas. After that, based on the information, it constructs the
+ * three regions and returns. For more detail, refer to the comment of
+ * 'damon_init_regions_of()' function definition in 'mm/damon.c' file.
+ *
+ * For example, suppose virtual address ranges of 10-20, 20-25, 200-210,
+ * 210-220, 300-305, and 307-330 (Other comments represent this mappings in
+ * more short form: 10-20-25, 200-210-220, 300-305, 307-330) of a process are
+ * mapped. To cover every mappings, the three regions should start with 10,
+ * and end with 305. The process also has three unmapped areas, 25-200,
+ * 220-300, and 305-307. Among those, 25-200 and 220-300 are the biggest two
+ * unmapped areas, and thus it should be converted to three regions of 10-25,
+ * 200-220, and 300-330.
+ */
+static void damon_test_three_regions_in_vmas(struct kunit *test)
+{
+ struct damon_addr_range regions[3] = {0,};
+ /* 10-20-25, 200-210-220, 300-305, 307-330 */
+ struct vm_area_struct vmas[] = {
+ (struct vm_area_struct) {.vm_start = 10, .vm_end = 20},
+ (struct vm_area_struct) {.vm_start = 20, .vm_end = 25},
+ (struct vm_area_struct) {.vm_start = 200, .vm_end = 210},
+ (struct vm_area_struct) {.vm_start = 210, .vm_end = 220},
+ (struct vm_area_struct) {.vm_start = 300, .vm_end = 305},
+ (struct vm_area_struct) {.vm_start = 307, .vm_end = 330},
+ };
+
+ __link_vmas(vmas, 6);
+
+ __damon_va_three_regions(&vmas[0], regions);
+
+ KUNIT_EXPECT_EQ(test, 10ul, regions[0].start);
+ KUNIT_EXPECT_EQ(test, 25ul, regions[0].end);
+ KUNIT_EXPECT_EQ(test, 200ul, regions[1].start);
+ KUNIT_EXPECT_EQ(test, 220ul, regions[1].end);
+ KUNIT_EXPECT_EQ(test, 300ul, regions[2].start);
+ KUNIT_EXPECT_EQ(test, 330ul, regions[2].end);
+}
+
+static struct damon_region *__nth_region_of(struct damon_target *t, int idx)
+{
+ struct damon_region *r;
+ unsigned int i = 0;
+
+ damon_for_each_region(r, t) {
+ if (i++ == idx)
+ return r;
+ }
+
+ return NULL;
+}
+
+/*
+ * Test 'damon_va_apply_three_regions()'
+ *
+ * test kunit object
+ * regions an array containing start/end addresses of current
+ * monitoring target regions
+ * nr_regions the number of the addresses in 'regions'
+ * three_regions The three regions that need to be applied now
+ * expected start/end addresses of monitoring target regions that
+ * 'three_regions' are applied
+ * nr_expected the number of addresses in 'expected'
+ *
+ * The memory mapping of the target processes changes dynamically. To follow
+ * the change, DAMON periodically reads the mappings, simplifies it to the
+ * three regions, and updates the monitoring target regions to fit in the three
+ * regions. The update of current target regions is the role of
+ * 'damon_va_apply_three_regions()'.
+ *
+ * This test passes the given target regions and the new three regions that
+ * need to be applied to the function and check whether it updates the regions
+ * as expected.
+ */
+static void damon_do_test_apply_three_regions(struct kunit *test,
+ unsigned long *regions, int nr_regions,
+ struct damon_addr_range *three_regions,
+ unsigned long *expected, int nr_expected)
+{
+ struct damon_ctx *ctx = damon_new_ctx();
+ struct damon_target *t;
+ struct damon_region *r;
+ int i;
+
+ t = damon_new_target(42);
+ for (i = 0; i < nr_regions / 2; i++) {
+ r = damon_new_region(regions[i * 2], regions[i * 2 + 1]);
+ damon_add_region(r, t);
+ }
+ damon_add_target(ctx, t);
+
+ damon_va_apply_three_regions(ctx, t, three_regions);
+
+ for (i = 0; i < nr_expected / 2; i++) {
+ r = __nth_region_of(t, i);
+ KUNIT_EXPECT_EQ(test, r->ar.start, expected[i * 2]);
+ KUNIT_EXPECT_EQ(test, r->ar.end, expected[i * 2 + 1]);
+ }
+
+ damon_destroy_ctx(ctx);
+}
+
+/*
+ * This function test most common case where the three big regions are only
+ * slightly changed. Target regions should adjust their boundary (10-20-30,
+ * 50-55, 70-80, 90-100) to fit with the new big regions or remove target
+ * regions (57-79) that now out of the three regions.
+ */
+static void damon_test_apply_three_regions1(struct kunit *test)
+{
+ /* 10-20-30, 50-55-57-59, 70-80-90-100 */
+ unsigned long regions[] = {10, 20, 20, 30, 50, 55, 55, 57, 57, 59,
+ 70, 80, 80, 90, 90, 100};
+ /* 5-27, 45-55, 73-104 */
+ struct damon_addr_range new_three_regions[3] = {
+ (struct damon_addr_range){.start = 5, .end = 27},
+ (struct damon_addr_range){.start = 45, .end = 55},
+ (struct damon_addr_range){.start = 73, .end = 104} };
+ /* 5-20-27, 45-55, 73-80-90-104 */
+ unsigned long expected[] = {5, 20, 20, 27, 45, 55,
+ 73, 80, 80, 90, 90, 104};
+
+ damon_do_test_apply_three_regions(test, regions, ARRAY_SIZE(regions),
+ new_three_regions, expected, ARRAY_SIZE(expected));
+}
+
+/*
+ * Test slightly bigger change. Similar to above, but the second big region
+ * now require two target regions (50-55, 57-59) to be removed.
+ */
+static void damon_test_apply_three_regions2(struct kunit *test)
+{
+ /* 10-20-30, 50-55-57-59, 70-80-90-100 */
+ unsigned long regions[] = {10, 20, 20, 30, 50, 55, 55, 57, 57, 59,
+ 70, 80, 80, 90, 90, 100};
+ /* 5-27, 56-57, 65-104 */
+ struct damon_addr_range new_three_regions[3] = {
+ (struct damon_addr_range){.start = 5, .end = 27},
+ (struct damon_addr_range){.start = 56, .end = 57},
+ (struct damon_addr_range){.start = 65, .end = 104} };
+ /* 5-20-27, 56-57, 65-80-90-104 */
+ unsigned long expected[] = {5, 20, 20, 27, 56, 57,
+ 65, 80, 80, 90, 90, 104};
+
+ damon_do_test_apply_three_regions(test, regions, ARRAY_SIZE(regions),
+ new_three_regions, expected, ARRAY_SIZE(expected));
+}
+
+/*
+ * Test a big change. The second big region has totally freed and mapped to
+ * different area (50-59 -> 61-63). The target regions which were in the old
+ * second big region (50-55-57-59) should be removed and new target region
+ * covering the second big region (61-63) should be created.
+ */
+static void damon_test_apply_three_regions3(struct kunit *test)
+{
+ /* 10-20-30, 50-55-57-59, 70-80-90-100 */
+ unsigned long regions[] = {10, 20, 20, 30, 50, 55, 55, 57, 57, 59,
+ 70, 80, 80, 90, 90, 100};
+ /* 5-27, 61-63, 65-104 */
+ struct damon_addr_range new_three_regions[3] = {
+ (struct damon_addr_range){.start = 5, .end = 27},
+ (struct damon_addr_range){.start = 61, .end = 63},
+ (struct damon_addr_range){.start = 65, .end = 104} };
+ /* 5-20-27, 61-63, 65-80-90-104 */
+ unsigned long expected[] = {5, 20, 20, 27, 61, 63,
+ 65, 80, 80, 90, 90, 104};
+
+ damon_do_test_apply_three_regions(test, regions, ARRAY_SIZE(regions),
+ new_three_regions, expected, ARRAY_SIZE(expected));
+}
+
+/*
+ * Test another big change. Both of the second and third big regions (50-59
+ * and 70-100) has totally freed and mapped to different area (30-32 and
+ * 65-68). The target regions which were in the old second and third big
+ * regions should now be removed and new target regions covering the new second
+ * and third big regions should be crated.
+ */
+static void damon_test_apply_three_regions4(struct kunit *test)
+{
+ /* 10-20-30, 50-55-57-59, 70-80-90-100 */
+ unsigned long regions[] = {10, 20, 20, 30, 50, 55, 55, 57, 57, 59,
+ 70, 80, 80, 90, 90, 100};
+ /* 5-7, 30-32, 65-68 */
+ struct damon_addr_range new_three_regions[3] = {
+ (struct damon_addr_range){.start = 5, .end = 7},
+ (struct damon_addr_range){.start = 30, .end = 32},
+ (struct damon_addr_range){.start = 65, .end = 68} };
+ /* expect 5-7, 30-32, 65-68 */
+ unsigned long expected[] = {5, 7, 30, 32, 65, 68};
+
+ damon_do_test_apply_three_regions(test, regions, ARRAY_SIZE(regions),
+ new_three_regions, expected, ARRAY_SIZE(expected));
+}
+
+static void damon_test_split_evenly(struct kunit *test)
+{
+ struct damon_ctx *c = damon_new_ctx();
+ struct damon_target *t;
+ struct damon_region *r;
+ unsigned long i;
+
+ KUNIT_EXPECT_EQ(test, damon_va_evenly_split_region(c, NULL, 5), -EINVAL);
+
+ t = damon_new_target(42);
+ r = damon_new_region(0, 100);
+ KUNIT_EXPECT_EQ(test, damon_va_evenly_split_region(c, r, 0), -EINVAL);
+
+ damon_add_region(r, t);
+ KUNIT_EXPECT_EQ(test, damon_va_evenly_split_region(c, r, 10), 0);
+ KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 10u);
+
+ i = 0;
+ damon_for_each_region(r, t) {
+ KUNIT_EXPECT_EQ(test, r->ar.start, i++ * 10);
+ KUNIT_EXPECT_EQ(test, r->ar.end, i * 10);
+ }
+ damon_free_target(t);
+
+ t = damon_new_target(42);
+ r = damon_new_region(5, 59);
+ damon_add_region(r, t);
+ KUNIT_EXPECT_EQ(test, damon_va_evenly_split_region(c, r, 5), 0);
+ KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 5u);
+
+ i = 0;
+ damon_for_each_region(r, t) {
+ if (i == 4)
+ break;
+ KUNIT_EXPECT_EQ(test, r->ar.start, 5 + 10 * i++);
+ KUNIT_EXPECT_EQ(test, r->ar.end, 5 + 10 * i);
+ }
+ KUNIT_EXPECT_EQ(test, r->ar.start, 5 + 10 * i);
+ KUNIT_EXPECT_EQ(test, r->ar.end, 59ul);
+ damon_free_target(t);
+
+ t = damon_new_target(42);
+ r = damon_new_region(5, 6);
+ damon_add_region(r, t);
+ KUNIT_EXPECT_EQ(test, damon_va_evenly_split_region(c, r, 2), -EINVAL);
+ KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 1u);
+
+ damon_for_each_region(r, t) {
+ KUNIT_EXPECT_EQ(test, r->ar.start, 5ul);
+ KUNIT_EXPECT_EQ(test, r->ar.end, 6ul);
+ }
+ damon_free_target(t);
+ damon_destroy_ctx(c);
+}
+
+static struct kunit_case damon_test_cases[] = {
+ KUNIT_CASE(damon_test_three_regions_in_vmas),
+ KUNIT_CASE(damon_test_apply_three_regions1),
+ KUNIT_CASE(damon_test_apply_three_regions2),
+ KUNIT_CASE(damon_test_apply_three_regions3),
+ KUNIT_CASE(damon_test_apply_three_regions4),
+ KUNIT_CASE(damon_test_split_evenly),
+ {},
+};
+
+static struct kunit_suite damon_test_suite = {
+ .name = "damon-primitives",
+ .test_cases = damon_test_cases,
+};
+kunit_test_suite(damon_test_suite);
+
+#endif /* _DAMON_VADDR_TEST_H */
+
+#endif /* CONFIG_DAMON_VADDR_KUNIT_TEST */
diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
index 3bc9dc9f0656..a0cd006b3ec5 100644
--- a/mm/damon/vaddr.c
+++ b/mm/damon/vaddr.c
@@ -15,6 +15,11 @@
#include <linux/sched/mm.h>
#include <linux/slab.h>
+#ifdef CONFIG_DAMON_VADDR_KUNIT_TEST
+#undef DAMON_MIN_REGION
+#define DAMON_MIN_REGION 1
+#endif
+
/* Get a random number in [l, r) */
#define damon_rand(l, r) (l + prandom_u32_max(r - l))
@@ -614,3 +619,5 @@ void damon_va_set_primitives(struct damon_ctx *ctx)
ctx->primitive.target_valid = damon_va_target_valid;
ctx->primitive.cleanup = damon_va_cleanup;
}
+
+#include "vaddr-test.h"
--
2.17.1
From: SeongJae Park <[email protected]>
DAMON is designed to be used by kernel space code such as the memory
management subsystems, and therefore it provides only kernel space API.
That said, letting the user space control DAMON could provide some
benefits to them. For example, it will allow user space to analyze
their specific workloads and make their own special optimizations.
For such cases, this commit implements a simple DAMON application kernel
module, namely 'damon-dbgfs', which merely wraps the DAMON api and
exports those to the user space via the debugfs.
'damon-dbgfs' exports three files, ``attrs``, ``target_ids``, and
``monitor_on`` under its debugfs directory, ``<debugfs>/damon/``.
Attributes
----------
Users can read and write the ``sampling interval``, ``aggregation
interval``, ``regions update interval``, and min/max number of
monitoring target regions by reading from and writing to the ``attrs``
file. For example, below commands set those values to 5 ms, 100 ms,
1,000 ms, 10, 1000 and check it again::
# cd <debugfs>/damon
# echo 5000 100000 1000000 10 1000 > attrs
# cat attrs
5000 100000 1000000 10 1000
Target IDs
----------
Some types of address spaces supports multiple monitoring target. For
example, the virtual memory address spaces monitoring can have multiple
processes as the monitoring targets. Users can set the targets by
writing relevant id values of the targets to, and get the ids of the
current targets by reading from the ``target_ids`` file. In case of the
virtual address spaces monitoring, the values should be pids of the
monitoring target processes. For example, below commands set processes
having pids 42 and 4242 as the monitoring targets and check it again::
# cd <debugfs>/damon
# echo 42 4242 > target_ids
# cat target_ids
42 4242
Note that setting the target ids doesn't start the monitoring.
Turning On/Off
--------------
Setting the files as described above doesn't incur effect unless you
explicitly start the monitoring. You can start, stop, and check the
current status of the monitoring by writing to and reading from the
``monitor_on`` file. Writing ``on`` to the file starts the monitoring
of the targets with the attributes. Writing ``off`` to the file stops
those. DAMON also stops if every targets are invalidated (in case of
the virtual memory monitoring, target processes are invalidated when
terminated). Below example commands turn on, off, and check the status
of DAMON::
# cd <debugfs>/damon
# echo on > monitor_on
# echo off > monitor_on
# cat monitor_on
off
Please note that you cannot write to the above-mentioned debugfs files
while the monitoring is turned on. If you write to the files while
DAMON is running, an error code such as ``-EBUSY`` will be returned.
Signed-off-by: SeongJae Park <[email protected]>
Reviewed-by: Leonard Foerster <[email protected]>
---
include/linux/damon.h | 3 +
mm/damon/Kconfig | 9 +
mm/damon/Makefile | 1 +
mm/damon/core.c | 47 ++++++
mm/damon/dbgfs.c | 382 ++++++++++++++++++++++++++++++++++++++++++
5 files changed, 442 insertions(+)
create mode 100644 mm/damon/dbgfs.c
diff --git a/include/linux/damon.h b/include/linux/damon.h
index 72cf5ebd35fe..b17e808a9cae 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -237,9 +237,12 @@ unsigned int damon_nr_regions(struct damon_target *t);
struct damon_ctx *damon_new_ctx(void);
void damon_destroy_ctx(struct damon_ctx *ctx);
+int damon_set_targets(struct damon_ctx *ctx,
+ unsigned long *ids, ssize_t nr_ids);
int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
unsigned long aggr_int, unsigned long primitive_upd_int,
unsigned long min_nr_reg, unsigned long max_nr_reg);
+int damon_nr_running_ctxs(void);
int damon_start(struct damon_ctx **ctxs, int nr_ctxs);
int damon_stop(struct damon_ctx **ctxs, int nr_ctxs);
diff --git a/mm/damon/Kconfig b/mm/damon/Kconfig
index 8ae080c52950..72f1683ba0ee 100644
--- a/mm/damon/Kconfig
+++ b/mm/damon/Kconfig
@@ -21,4 +21,13 @@ config DAMON_VADDR
This builds the default data access monitoring primitives for DAMON
that works for virtual address spaces.
+config DAMON_DBGFS
+ bool "DAMON debugfs interface"
+ depends on DAMON_VADDR && DEBUG_FS
+ help
+ This builds the debugfs interface for DAMON. The user space admins
+ can use the interface for arbitrary data access monitoring.
+
+ If unsure, say N.
+
endmenu
diff --git a/mm/damon/Makefile b/mm/damon/Makefile
index 6ebbd08aed67..fed4be3bace3 100644
--- a/mm/damon/Makefile
+++ b/mm/damon/Makefile
@@ -2,3 +2,4 @@
obj-$(CONFIG_DAMON) := core.o
obj-$(CONFIG_DAMON_VADDR) += vaddr.o
+obj-$(CONFIG_DAMON_DBGFS) += dbgfs.o
diff --git a/mm/damon/core.c b/mm/damon/core.c
index 912112662d0c..cad2b4cee39d 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -172,6 +172,39 @@ void damon_destroy_ctx(struct damon_ctx *ctx)
kfree(ctx);
}
+/**
+ * damon_set_targets() - Set monitoring targets.
+ * @ctx: monitoring context
+ * @ids: array of target ids
+ * @nr_ids: number of entries in @ids
+ *
+ * This function should not be called while the kdamond is running.
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+int damon_set_targets(struct damon_ctx *ctx,
+ unsigned long *ids, ssize_t nr_ids)
+{
+ ssize_t i;
+ struct damon_target *t, *next;
+
+ damon_destroy_targets(ctx);
+
+ for (i = 0; i < nr_ids; i++) {
+ t = damon_new_target(ids[i]);
+ if (!t) {
+ pr_err("Failed to alloc damon_target\n");
+ /* The caller should do cleanup of the ids itself */
+ damon_for_each_target_safe(t, next, ctx)
+ damon_destroy_target(t);
+ return -ENOMEM;
+ }
+ damon_add_target(ctx, t);
+ }
+
+ return 0;
+}
+
/**
* damon_set_attrs() - Set attributes for the monitoring.
* @ctx: monitoring context
@@ -210,6 +243,20 @@ int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
return 0;
}
+/**
+ * damon_nr_running_ctxs() - Return number of currently running contexts.
+ */
+int damon_nr_running_ctxs(void)
+{
+ int nr_ctxs;
+
+ mutex_lock(&damon_lock);
+ nr_ctxs = nr_running_ctxs;
+ mutex_unlock(&damon_lock);
+
+ return nr_ctxs;
+}
+
/* Returns the size upper limit for each monitoring region */
static unsigned long damon_region_sz_limit(struct damon_ctx *ctx)
{
diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
new file mode 100644
index 000000000000..9af844faffd4
--- /dev/null
+++ b/mm/damon/dbgfs.c
@@ -0,0 +1,382 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * DAMON Debugfs Interface
+ *
+ * Author: SeongJae Park <[email protected]>
+ */
+
+#define pr_fmt(fmt) "damon-dbgfs: " fmt
+
+#include <linux/damon.h>
+#include <linux/debugfs.h>
+#include <linux/file.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/page_idle.h>
+#include <linux/slab.h>
+
+static struct damon_ctx **dbgfs_ctxs;
+static int dbgfs_nr_ctxs;
+static struct dentry **dbgfs_dirs;
+
+/*
+ * Returns non-empty string on success, negarive error code otherwise.
+ */
+static char *user_input_str(const char __user *buf, size_t count, loff_t *ppos)
+{
+ char *kbuf;
+ ssize_t ret;
+
+ /* We do not accept continuous write */
+ if (*ppos)
+ return ERR_PTR(-EINVAL);
+
+ kbuf = kmalloc(count + 1, GFP_KERNEL);
+ if (!kbuf)
+ return ERR_PTR(-ENOMEM);
+
+ ret = simple_write_to_buffer(kbuf, count + 1, ppos, buf, count);
+ if (ret != count) {
+ kfree(kbuf);
+ return ERR_PTR(-EIO);
+ }
+ kbuf[ret] = '\0';
+
+ return kbuf;
+}
+
+static ssize_t dbgfs_attrs_read(struct file *file,
+ char __user *buf, size_t count, loff_t *ppos)
+{
+ struct damon_ctx *ctx = file->private_data;
+ char kbuf[128];
+ int ret;
+
+ mutex_lock(&ctx->kdamond_lock);
+ ret = scnprintf(kbuf, ARRAY_SIZE(kbuf), "%lu %lu %lu %lu %lu\n",
+ ctx->sample_interval, ctx->aggr_interval,
+ ctx->primitive_update_interval, ctx->min_nr_regions,
+ ctx->max_nr_regions);
+ mutex_unlock(&ctx->kdamond_lock);
+
+ return simple_read_from_buffer(buf, count, ppos, kbuf, ret);
+}
+
+static ssize_t dbgfs_attrs_write(struct file *file,
+ const char __user *buf, size_t count, loff_t *ppos)
+{
+ struct damon_ctx *ctx = file->private_data;
+ unsigned long s, a, r, minr, maxr;
+ char *kbuf;
+ ssize_t ret = count;
+ int err;
+
+ kbuf = user_input_str(buf, count, ppos);
+ if (IS_ERR(kbuf))
+ return PTR_ERR(kbuf);
+
+ if (sscanf(kbuf, "%lu %lu %lu %lu %lu",
+ &s, &a, &r, &minr, &maxr) != 5) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ mutex_lock(&ctx->kdamond_lock);
+ if (ctx->kdamond) {
+ ret = -EBUSY;
+ goto unlock_out;
+ }
+
+ err = damon_set_attrs(ctx, s, a, r, minr, maxr);
+ if (err)
+ ret = err;
+unlock_out:
+ mutex_unlock(&ctx->kdamond_lock);
+out:
+ kfree(kbuf);
+ return ret;
+}
+
+#define targetid_is_pid(ctx) \
+ (ctx->primitive.target_valid == damon_va_target_valid)
+
+static ssize_t sprint_target_ids(struct damon_ctx *ctx, char *buf, ssize_t len)
+{
+ struct damon_target *t;
+ unsigned long id;
+ int written = 0;
+ int rc;
+
+ damon_for_each_target(t, ctx) {
+ id = t->id;
+ if (targetid_is_pid(ctx))
+ /* Show pid numbers to debugfs users */
+ id = (unsigned long)pid_vnr((struct pid *)id);
+
+ rc = scnprintf(&buf[written], len - written, "%lu ", id);
+ if (!rc)
+ return -ENOMEM;
+ written += rc;
+ }
+ if (written)
+ written -= 1;
+ written += scnprintf(&buf[written], len - written, "\n");
+ return written;
+}
+
+static ssize_t dbgfs_target_ids_read(struct file *file,
+ char __user *buf, size_t count, loff_t *ppos)
+{
+ struct damon_ctx *ctx = file->private_data;
+ ssize_t len;
+ char ids_buf[320];
+
+ mutex_lock(&ctx->kdamond_lock);
+ len = sprint_target_ids(ctx, ids_buf, 320);
+ mutex_unlock(&ctx->kdamond_lock);
+ if (len < 0)
+ return len;
+
+ return simple_read_from_buffer(buf, count, ppos, ids_buf, len);
+}
+
+/*
+ * Converts a string into an array of unsigned long integers
+ *
+ * Returns an array of unsigned long integers if the conversion success, or
+ * NULL otherwise.
+ */
+static unsigned long *str_to_target_ids(const char *str, ssize_t len,
+ ssize_t *nr_ids)
+{
+ unsigned long *ids;
+ const int max_nr_ids = 32;
+ unsigned long id;
+ int pos = 0, parsed, ret;
+
+ *nr_ids = 0;
+ ids = kmalloc_array(max_nr_ids, sizeof(id), GFP_KERNEL);
+ if (!ids)
+ return NULL;
+ while (*nr_ids < max_nr_ids && pos < len) {
+ ret = sscanf(&str[pos], "%lu%n", &id, &parsed);
+ pos += parsed;
+ if (ret != 1)
+ break;
+ ids[*nr_ids] = id;
+ *nr_ids += 1;
+ }
+
+ return ids;
+}
+
+static void dbgfs_put_pids(unsigned long *ids, int nr_ids)
+{
+ int i;
+
+ for (i = 0; i < nr_ids; i++)
+ put_pid((struct pid *)ids[i]);
+}
+
+static ssize_t dbgfs_target_ids_write(struct file *file,
+ const char __user *buf, size_t count, loff_t *ppos)
+{
+ struct damon_ctx *ctx = file->private_data;
+ char *kbuf, *nrs;
+ unsigned long *targets;
+ ssize_t nr_targets;
+ ssize_t ret = count;
+ int i;
+ int err;
+
+ kbuf = user_input_str(buf, count, ppos);
+ if (IS_ERR(kbuf))
+ return PTR_ERR(kbuf);
+
+ nrs = kbuf;
+
+ targets = str_to_target_ids(nrs, ret, &nr_targets);
+ if (!targets) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ if (targetid_is_pid(ctx)) {
+ for (i = 0; i < nr_targets; i++) {
+ targets[i] = (unsigned long)find_get_pid(
+ (int)targets[i]);
+ if (!targets[i]) {
+ dbgfs_put_pids(targets, i);
+ ret = -EINVAL;
+ goto free_targets_out;
+ }
+ }
+ }
+
+ mutex_lock(&ctx->kdamond_lock);
+ if (ctx->kdamond) {
+ if (targetid_is_pid(ctx))
+ dbgfs_put_pids(targets, nr_targets);
+ ret = -EBUSY;
+ goto unlock_out;
+ }
+
+ err = damon_set_targets(ctx, targets, nr_targets);
+ if (err) {
+ if (targetid_is_pid(ctx))
+ dbgfs_put_pids(targets, nr_targets);
+ ret = err;
+ }
+
+unlock_out:
+ mutex_unlock(&ctx->kdamond_lock);
+free_targets_out:
+ kfree(targets);
+out:
+ kfree(kbuf);
+ return ret;
+}
+
+static int damon_dbgfs_open(struct inode *inode, struct file *file)
+{
+ file->private_data = inode->i_private;
+
+ return nonseekable_open(inode, file);
+}
+
+static const struct file_operations attrs_fops = {
+ .owner = THIS_MODULE,
+ .open = damon_dbgfs_open,
+ .read = dbgfs_attrs_read,
+ .write = dbgfs_attrs_write,
+};
+
+static const struct file_operations target_ids_fops = {
+ .owner = THIS_MODULE,
+ .open = damon_dbgfs_open,
+ .read = dbgfs_target_ids_read,
+ .write = dbgfs_target_ids_write,
+};
+
+static int dbgfs_fill_ctx_dir(struct dentry *dir, struct damon_ctx *ctx)
+{
+ const char * const file_names[] = {"attrs", "target_ids"};
+ const struct file_operations *fops[] = {&attrs_fops, &target_ids_fops};
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(file_names); i++)
+ debugfs_create_file(file_names[i], 0600, dir, ctx, fops[i]);
+
+ return 0;
+}
+
+static struct damon_ctx *dbgfs_new_ctx(void)
+{
+ struct damon_ctx *ctx;
+
+ ctx = damon_new_ctx();
+ if (!ctx)
+ return NULL;
+
+ damon_va_set_primitives(ctx);
+ return ctx;
+}
+
+static ssize_t dbgfs_monitor_on_read(struct file *file,
+ char __user *buf, size_t count, loff_t *ppos)
+{
+ char monitor_on_buf[5];
+ bool monitor_on = damon_nr_running_ctxs() != 0;
+ int len;
+
+ len = scnprintf(monitor_on_buf, 5, monitor_on ? "on\n" : "off\n");
+
+ return simple_read_from_buffer(buf, count, ppos, monitor_on_buf, len);
+}
+
+static ssize_t dbgfs_monitor_on_write(struct file *file,
+ const char __user *buf, size_t count, loff_t *ppos)
+{
+ ssize_t ret = count;
+ char *kbuf;
+ int err;
+
+ kbuf = user_input_str(buf, count, ppos);
+ if (IS_ERR(kbuf))
+ return PTR_ERR(kbuf);
+
+ /* Remove white space */
+ if (sscanf(kbuf, "%s", kbuf) != 1) {
+ kfree(kbuf);
+ return -EINVAL;
+ }
+
+ if (!strncmp(kbuf, "on", count))
+ err = damon_start(dbgfs_ctxs, dbgfs_nr_ctxs);
+ else if (!strncmp(kbuf, "off", count))
+ err = damon_stop(dbgfs_ctxs, dbgfs_nr_ctxs);
+ else
+ err = -EINVAL;
+
+ if (err)
+ ret = err;
+ kfree(kbuf);
+ return ret;
+}
+
+static const struct file_operations monitor_on_fops = {
+ .owner = THIS_MODULE,
+ .read = dbgfs_monitor_on_read,
+ .write = dbgfs_monitor_on_write,
+};
+
+static int __init __damon_dbgfs_init(void)
+{
+ struct dentry *dbgfs_root;
+ const char * const file_names[] = {"monitor_on"};
+ const struct file_operations *fops[] = {&monitor_on_fops};
+ int i;
+
+ dbgfs_root = debugfs_create_dir("damon", NULL);
+
+ for (i = 0; i < ARRAY_SIZE(file_names); i++)
+ debugfs_create_file(file_names[i], 0600, dbgfs_root, NULL,
+ fops[i]);
+ dbgfs_fill_ctx_dir(dbgfs_root, dbgfs_ctxs[0]);
+
+ dbgfs_dirs = kmalloc_array(1, sizeof(dbgfs_root), GFP_KERNEL);
+ if (!dbgfs_dirs)
+ return -ENOMEM;
+ dbgfs_dirs[0] = dbgfs_root;
+
+ return 0;
+}
+
+/*
+ * Functions for the initialization
+ */
+
+static int __init damon_dbgfs_init(void)
+{
+ int rc;
+
+ dbgfs_ctxs = kmalloc(sizeof(*dbgfs_ctxs), GFP_KERNEL);
+ if (!dbgfs_ctxs) {
+ pr_err("%s: dbgfs ctxs alloc failed\n", __func__);
+ return -ENOMEM;
+ }
+ dbgfs_ctxs[0] = dbgfs_new_ctx();
+ if (!dbgfs_ctxs[0]) {
+ pr_err("%s: dbgfs ctx alloc failed\n", __func__);
+ return -ENOMEM;
+ }
+ dbgfs_nr_ctxs = 1;
+
+ rc = __damon_dbgfs_init();
+ if (rc)
+ pr_err("%s: dbgfs init failed\n", __func__);
+
+ return rc;
+}
+
+module_init(damon_dbgfs_init);
--
2.17.1
From: SeongJae Park <[email protected]>
This commit adds documents for DAMON under
`Documentation/admin-guide/mm/damon/` and `Documentation/vm/damon/`.
Signed-off-by: SeongJae Park <[email protected]>
---
Documentation/admin-guide/mm/damon/guide.rst | 158 +++++++++++++
Documentation/admin-guide/mm/damon/index.rst | 15 ++
Documentation/admin-guide/mm/damon/plans.rst | 29 +++
Documentation/admin-guide/mm/damon/start.rst | 114 +++++++++
Documentation/admin-guide/mm/damon/usage.rst | 112 +++++++++
Documentation/admin-guide/mm/index.rst | 1 +
Documentation/vm/damon/api.rst | 20 ++
Documentation/vm/damon/design.rst | 166 +++++++++++++
Documentation/vm/damon/eval.rst | 232 +++++++++++++++++++
Documentation/vm/damon/faq.rst | 58 +++++
Documentation/vm/damon/index.rst | 31 +++
Documentation/vm/index.rst | 1 +
12 files changed, 937 insertions(+)
create mode 100644 Documentation/admin-guide/mm/damon/guide.rst
create mode 100644 Documentation/admin-guide/mm/damon/index.rst
create mode 100644 Documentation/admin-guide/mm/damon/plans.rst
create mode 100644 Documentation/admin-guide/mm/damon/start.rst
create mode 100644 Documentation/admin-guide/mm/damon/usage.rst
create mode 100644 Documentation/vm/damon/api.rst
create mode 100644 Documentation/vm/damon/design.rst
create mode 100644 Documentation/vm/damon/eval.rst
create mode 100644 Documentation/vm/damon/faq.rst
create mode 100644 Documentation/vm/damon/index.rst
diff --git a/Documentation/admin-guide/mm/damon/guide.rst b/Documentation/admin-guide/mm/damon/guide.rst
new file mode 100644
index 000000000000..f52dc1669bb1
--- /dev/null
+++ b/Documentation/admin-guide/mm/damon/guide.rst
@@ -0,0 +1,158 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==================
+Optimization Guide
+==================
+
+This document helps you estimating the amount of benefit that you could get
+from DAMON-based optimizations, and describes how you could achieve it. You
+are assumed to already read :doc:`start`.
+
+
+Check The Signs
+===============
+
+No optimization can provide same extent of benefit to every case. Therefore
+you should first guess how much improvements you could get using DAMON. If
+some of below conditions match your situation, you could consider using DAMON.
+
+- *Low IPC and High Cache Miss Ratios.* Low IPC means most of the CPU time is
+ spent waiting for the completion of time-consuming operations such as memory
+ access, while high cache miss ratios mean the caches don't help it well.
+ DAMON is not for cache level optimization, but DRAM level. However,
+ improving DRAM management will also help this case by reducing the memory
+ operation latency.
+- *Memory Over-commitment and Unknown Users.* If you are doing memory
+ overcommitment and you cannot control every user of your system, a memory
+ bank run could happen at any time. You can estimate when it will happen
+ based on DAMON's monitoring results and act earlier to avoid or deal better
+ with the crisis.
+- *Frequent Memory Pressure.* Frequent memory pressure means your system has
+ wrong configurations or memory hogs. DAMON will help you find the right
+ configuration and/or the criminals.
+- *Heterogeneous Memory System.* If your system is utilizing memory devices
+ that placed between DRAM and traditional hard disks, such as non-volatile
+ memory or fast SSDs, DAMON could help you utilizing the devices more
+ efficiently.
+
+
+Profile
+=======
+
+If you found some positive signals, you could start by profiling your workloads
+using DAMON. Find major workloads on your systems and analyze their data
+access pattern to find something wrong or can be improved. The DAMON user
+space tool (``damo``) will be useful for this. You can get ``damo`` from
+https://github.com/awslabs/damo.
+
+We recommend you to start from working set size distribution check using ``damo
+report wss``. If the distribution is ununiform or quite different from what
+you estimated, you could consider `Memory Configuration`_ optimization.
+
+Then, review the overall access pattern in heatmap form using ``damo report
+heats``. If it shows a simple pattern consists of a small number of memory
+regions having high contrast of access temperature, you could consider manual
+`Program Modification`_.
+
+If you still want to absorb more benefits, you should develop `Personalized
+DAMON Application`_ for your special case.
+
+You don't need to take only one approach among the above plans, but you could
+use multiple of the above approaches to maximize the benefit.
+
+
+Optimize
+========
+
+If the profiling result also says it's worth trying some optimization, you
+could consider below approaches. Note that some of the below approaches assume
+that your systems are configured with swap devices or other types of auxiliary
+memory so that you don't strictly required to accommodate the whole working set
+in the main memory. Most of the detailed optimization should be made on your
+concrete understanding of your memory devices.
+
+
+Memory Configuration
+--------------------
+
+No more no less, DRAM should be large enough to accommodate only important
+working sets, because DRAM is highly performance critical but expensive and
+heavily consumes the power. However, knowing the size of the real important
+working sets is difficult. As a consequence, people usually equips
+unnecessarily large or too small DRAM. Many problems stem from such wrong
+configurations.
+
+Using the working set size distribution report provided by ``damo report wss``,
+you can know the appropriate DRAM size for you. For example, roughly speaking,
+if you worry about only 95 percentile latency, you don't need to equip DRAM of
+a size larger than 95 percentile working set size.
+
+Let's see a real example. This `page
+<https://damonitor.github.io/doc/html/v17/admin-guide/mm/damon/guide.html#memory-configuration>`_
+shows the heatmap and the working set size distributions/changes of
+``freqmine`` workload in PARSEC3 benchmark suite. The working set size spikes
+up to 180 MiB, but keeps smaller than 50 MiB for more than 95% of the time.
+Even though you give only 50 MiB of memory space to the workload, it will work
+well for 95% of the time. Meanwhile, you can save the 130 MiB of memory space.
+
+
+Program Modification
+--------------------
+
+If the data access pattern heatmap plotted by ``damo report heats`` is quite
+simple so that you can understand how the things are going in the workload with
+your human eye, you could manually optimize the memory management.
+
+For example, suppose that the workload has two big memory object but only one
+object is frequently accessed while the other one is only occasionally
+accessed. Then, you could modify the program source code to keep the hot
+object in the main memory by invoking ``mlock()`` or ``madvise()`` with
+``MADV_WILLNEED``. Or, you could proactively evict the cold object using
+``madvise()`` with ``MADV_COLD`` or ``MADV_PAGEOUT``. Using both together
+would be also worthy.
+
+A research work [1]_ using the ``mlock()`` achieved up to 2.55x performance
+speedup.
+
+Let's see another realistic example access pattern for this kind of
+optimizations. This `page
+<https://damonitor.github.io/doc/html/v17/admin-guide/mm/damon/guide.html#program-modification>`_
+shows the visualized access patterns of streamcluster workload in PARSEC3
+benchmark suite. We can easily identify the 100 MiB sized hot object.
+
+
+Personalized DAMON Application
+------------------------------
+
+Above approaches will work well for many general cases, but would not enough
+for some special cases.
+
+If this is the case, it might be the time to forget the comfortable use of the
+user space tool and dive into the debugfs interface (refer to :doc:`usage` for
+the detail) of DAMON. Using the interface, you can control the DAMON more
+flexibly. Therefore, you can write your personalized DAMON application that
+controls the monitoring via the debugfs interface, analyzes the result, and
+applies complex optimizations itself. Using this, you can make more creative
+and wise optimizations.
+
+If you are a kernel space programmer, writing kernel space DAMON applications
+using the API (refer to the :doc:`/vm/damon/api` for more detail) would be an
+option.
+
+
+Reference Practices
+===================
+
+Referencing previously done successful practices could help you getting the
+sense for this kind of optimizations. There is an academic paper [1]_
+reporting the visualized access pattern and manual `Program
+Modification`_ results for a number of realistic workloads. You can also get
+the visualized access patterns [3]_ [4]_ [5]_ and automated DAMON-based memory
+operations results for other realistic workloads that collected with latest
+version of DAMON [2]_ .
+
+.. [1] https://dl.acm.org/doi/10.1145/3366626.3368125
+.. [2] https://damonitor.github.io/test/result/perf/latest/html/
+.. [3] https://damonitor.github.io/test/result/visual/latest/rec.heatmap.1.png.html
+.. [4] https://damonitor.github.io/test/result/visual/latest/rec.wss_sz.png.html
+.. [5] https://damonitor.github.io/test/result/visual/latest/rec.wss_time.png.html
diff --git a/Documentation/admin-guide/mm/damon/index.rst b/Documentation/admin-guide/mm/damon/index.rst
new file mode 100644
index 000000000000..0baae7a5402b
--- /dev/null
+++ b/Documentation/admin-guide/mm/damon/index.rst
@@ -0,0 +1,15 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+========================
+Monitoring Data Accesses
+========================
+
+:doc:`DAMON </vm/damon/index>` allows light-weight data access monitoring.
+Using this, users can analyze and optimize their systems.
+
+.. toctree::
+ :maxdepth: 2
+
+ start
+ guide
+ usage
diff --git a/Documentation/admin-guide/mm/damon/plans.rst b/Documentation/admin-guide/mm/damon/plans.rst
new file mode 100644
index 000000000000..e3aa5ab96c29
--- /dev/null
+++ b/Documentation/admin-guide/mm/damon/plans.rst
@@ -0,0 +1,29 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+============
+Future Plans
+============
+
+DAMON is still on its first stage. Below plans are still under development.
+
+
+Automate Data Access Monitoring-based Memory Operation Schemes Execution
+========================================================================
+
+The ultimate goal of DAMON is to be used as a building block for the data
+access pattern aware kernel memory management optimization. It will make
+system just works efficiently. However, some users having very special
+workloads will want to further do their own optimization. DAMON will automate
+most of the tasks for such manual optimizations in near future. Users will be
+required to only describe what kind of data access pattern-based operation
+schemes they want in a simple form.
+
+By applying a very simple scheme for THP promotion/demotion with a prototype
+implementation, DAMON reduced 60% of THP memory footprint overhead while
+preserving 50% of the THP performance benefit. The detailed results can be
+seen on an external web page [1]_.
+
+Several RFC patchsets for this plan are available [2]_.
+
+.. [1] https://damonitor.github.io/test/result/perf/latest/html/
+.. [2] https://lore.kernel.org/linux-mm/[email protected]/
diff --git a/Documentation/admin-guide/mm/damon/start.rst b/Documentation/admin-guide/mm/damon/start.rst
new file mode 100644
index 000000000000..62675cf1cb72
--- /dev/null
+++ b/Documentation/admin-guide/mm/damon/start.rst
@@ -0,0 +1,114 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===============
+Getting Started
+===============
+
+This document briefly describes how you can use DAMON by demonstrating its
+default user space tool. Please note that this document describes only a part
+of its features for brevity. Please refer to :doc:`usage` for more details.
+
+
+TL; DR
+======
+
+Follow below commands to monitor and visualize the access pattern of your
+workload. ::
+
+ # # build the kernel with CONFIG_DAMON_*=y, install it, and reboot
+ # mount -t debugfs none /sys/kernel/debug/
+ # git clone https://github.com/awslabs/damo
+ # ./damo/damo record $(pidof <your workload>)
+ # ./damo/damo report heat --plot_ascii
+
+The final command draws the access heatmap of ``<your workload>``, heatmap,
+which shows when (y-axis) what memory region (x-axis) is how frequently
+accessed (number).
+
+ 111111111111111111111111111111111111111111111111111111110000
+ 111121111111111111111111111111211111111111111111111111110000
+ 000000000000000000000000000000000000000000000000001555552000
+ 000000000000000000000000000000000000000000000222223555552000
+ 000000000000000000000000000000000000000011111677775000000000
+ 000000000000000000000000000000000000000488888000000000000000
+ 000000000000000000000000000000000177888400000000000000000000
+ 000000000000000000000000000046666522222100000000000000000000
+ 000000000000000000000014444344444300000000000000000000000000
+ 000000000000000002222245555510000000000000000000000000000000
+ # access_frequency: 0 1 2 3 4 5 6 7 8 9
+ # x-axis: space (140286319947776-140286426374096: 101.496 MiB)
+ # y-axis: time (605442256436361-605479951866441: 37.695430s)
+ # resolution: 60x10 (1.692 MiB and 3.770s for each character)
+
+
+Prerequisites
+=============
+
+Kernel
+------
+
+You should first ensure your system is running on a kernel built with
+``CONFIG_DAMON_*=y``.
+
+
+User Space Tool
+---------------
+
+For the demonstration, we will use the default user space tool for DAMON,
+called DAMON Operator (DAMO). It is available at
+https://github.com/awslabs/damo. For brevity, below examples assume you set
+``$PATH`` to point it. It's not mandatory, though.
+
+Because DAMO is using the debugfs interface (refer to :doc:`usage` for the
+detail) of DAMON, you should ensure debugfs is mounted. Mount it manually as
+below::
+
+ # mount -t debugfs none /sys/kernel/debug/
+
+or append below line to your ``/etc/fstab`` file so that your system can
+automatically mount debugfs from next booting::
+
+ debugfs /sys/kernel/debug debugfs defaults 0 0
+
+
+Recording Data Access Patterns
+==============================
+
+Below commands record memory access pattern of a program and save the
+monitoring results in a file. ::
+
+ $ git clone https://github.com/sjp38/masim
+ $ cd masim; make; ./masim ./configs/zigzag.cfg &
+ $ sudo damo record -o damon.data $(pidof masim)
+
+The first two lines of the commands get an artificial memory access generator
+program and runs it in the background. It will repeatedly access two 100 MiB
+sized memory regions one by one. You can substitute this with your real
+workload. The last line asks ``damo`` to record the access pattern in
+``damon.data`` file.
+
+
+Visualizing Recorded Patterns
+=============================
+
+Below three commands visualize the recorded access patterns into three
+image files. ::
+
+ $ damo report heats --heatmap access_pattern_heatmap.png
+ $ damo report wss --range 0 101 1 --plot wss_dist.png
+ $ damo report wss --range 0 101 1 --sortby time --plot wss_chron_change.png
+
+- ``access_pattern_heatmap.png`` will show the data access pattern in a
+ heatmap, which shows when (x-axis) what memory region (y-axis) is how
+ frequently accessed (color).
+- ``wss_dist.png`` will show the distribution of the working set size.
+- ``wss_chron_change.png`` will show how the working set size has
+ chronologically changed.
+
+You can show the images in a web page [1]_ . Those made with other realistic
+workloads are also available [2]_ [3]_ [4]_.
+
+.. [1] https://damonitor.github.io/doc/html/v17/admin-guide/mm/damon/start.html#visualizing-recorded-patterns
+.. [2] https://damonitor.github.io/test/result/visual/latest/rec.heatmap.1.png.html
+.. [3] https://damonitor.github.io/test/result/visual/latest/rec.wss_sz.png.html
+.. [4] https://damonitor.github.io/test/result/visual/latest/rec.wss_time.png.html
diff --git a/Documentation/admin-guide/mm/damon/usage.rst b/Documentation/admin-guide/mm/damon/usage.rst
new file mode 100644
index 000000000000..ea3fa6e55f8b
--- /dev/null
+++ b/Documentation/admin-guide/mm/damon/usage.rst
@@ -0,0 +1,112 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===============
+Detailed Usages
+===============
+
+DAMON provides below three interfaces for different users.
+
+- *DAMON user space tool.*
+ This is for privileged people such as system administrators who want a
+ just-working human-friendly interface. Using this, users can use the DAMON’s
+ major features in a human-friendly way. It may not be highly tuned for
+ special cases, though. It supports only virtual address spaces monitoring.
+- *debugfs interface.*
+ This is for privileged user space programmers who want more optimized use of
+ DAMON. Using this, users can use DAMON’s major features by reading
+ from and writing to special debugfs files. Therefore, you can write and use
+ your personalized DAMON debugfs wrapper programs that reads/writes the
+ debugfs files instead of you. The DAMON user space tool is also a reference
+ implementation of such programs. It supports only virtual address spaces
+ monitoring.
+- *Kernel Space Programming Interface.*
+ This is for kernel space programmers. Using this, users can utilize every
+ feature of DAMON most flexibly and efficiently by writing kernel space
+ DAMON application programs for you. You can even extend DAMON for various
+ address spaces.
+
+Nevertheless, you could write your own user space tool using the debugfs
+interface. A reference implementation is available at
+https://github.com/awslabs/damo. If you are a kernel programmer, you could
+refer to :doc:`/vm/damon/api` for the kernel space programming interface. For
+the reason, this document describes only the debugfs interface
+
+debugfs Interface
+=================
+
+DAMON exports three files, ``attrs``, ``target_ids``, and ``monitor_on`` under
+its debugfs directory, ``<debugfs>/damon/``.
+
+
+Attributes
+----------
+
+Users can get and set the ``sampling interval``, ``aggregation interval``,
+``regions update interval``, and min/max number of monitoring target regions by
+reading from and writing to the ``attrs`` file. To know about the monitoring
+attributes in detail, please refer to the :doc:`/vm/damon/design`. For
+example, below commands set those values to 5 ms, 100 ms, 1,000 ms, 10 and
+1000, and then check it again::
+
+ # cd <debugfs>/damon
+ # echo 5000 100000 1000000 10 1000 > attrs
+ # cat attrs
+ 5000 100000 1000000 10 1000
+
+
+Target IDs
+----------
+
+Some types of address spaces supports multiple monitoring target. For example,
+the virtual memory address spaces monitoring can have multiple processes as the
+monitoring targets. Users can set the targets by writing relevant id values of
+the targets to, and get the ids of the current targets by reading from the
+``target_ids`` file. In case of the virtual address spaces monitoring, the
+values should be pids of the monitoring target processes. For example, below
+commands set processes having pids 42 and 4242 as the monitoring targets and
+check it again::
+
+ # cd <debugfs>/damon
+ # echo 42 4242 > target_ids
+ # cat target_ids
+ 42 4242
+
+Note that setting the target ids doesn't start the monitoring.
+
+
+Turning On/Off
+--------------
+
+Setting the files as described above doesn't incur effect unless you explicitly
+start the monitoring. You can start, stop, and check the current status of the
+monitoring by writing to and reading from the ``monitor_on`` file. Writing
+``on`` to the file starts the monitoring of the targets with the attributes.
+Writing ``off`` to the file stops those. DAMON also stops if every target
+process is terminated. Below example commands turn on, off, and check the
+status of DAMON::
+
+ # cd <debugfs>/damon
+ # echo on > monitor_on
+ # echo off > monitor_on
+ # cat monitor_on
+ off
+
+Please note that you cannot write to the above-mentioned debugfs files while
+the monitoring is turned on. If you write to the files while DAMON is running,
+an error code such as ``-EBUSY`` will be returned.
+
+
+Tracepoint for Monitoring Results
+=================================
+
+DAMON provides the monitoring results via a tracepoint,
+``damon:damon_aggregated``. While the monitoring is turned on, you could
+record the tracepoint events and show results using tracepoint supporting tools
+like ``perf``. For example::
+
+ # echo on > monitor_on
+ # perf record damon:damon_aggregated &
+ # sleep 5
+ # kill 9 $(pidof perf)
+ # echo off > monitor_on
+ # perf script
diff --git a/Documentation/admin-guide/mm/index.rst b/Documentation/admin-guide/mm/index.rst
index 4b14d8b50e9e..cbd19d5e625f 100644
--- a/Documentation/admin-guide/mm/index.rst
+++ b/Documentation/admin-guide/mm/index.rst
@@ -27,6 +27,7 @@ the Linux memory management.
concepts
cma_debugfs
+ damon/index
hugetlbpage
idle_page_tracking
ksm
diff --git a/Documentation/vm/damon/api.rst b/Documentation/vm/damon/api.rst
new file mode 100644
index 000000000000..08f34df45523
--- /dev/null
+++ b/Documentation/vm/damon/api.rst
@@ -0,0 +1,20 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=============
+API Reference
+=============
+
+Kernel space programs can use every feature of DAMON using below APIs. All you
+need to do is including ``damon.h``, which is located in ``include/linux/`` of
+the source tree.
+
+Structures
+==========
+
+.. kernel-doc:: include/linux/damon.h
+
+
+Functions
+=========
+
+.. kernel-doc:: mm/damon/core.c
diff --git a/Documentation/vm/damon/design.rst b/Documentation/vm/damon/design.rst
new file mode 100644
index 000000000000..727d72093f8f
--- /dev/null
+++ b/Documentation/vm/damon/design.rst
@@ -0,0 +1,166 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+======
+Design
+======
+
+Configurable Layers
+===================
+
+DAMON provides data access monitoring functionality while making the accuracy
+and the overhead controllable. The fundamental access monitorings require
+primitives that dependent on and optimized for the target address space. On
+the other hand, the accuracy and overhead tradeoff mechanism, which is the core
+of DAMON, is in the pure logic space. DAMON separates the two parts in
+different layers and defines its interface to allow various low level
+primitives implementations configurable with the core logic.
+
+Due to this separated design and the configurable interface, users can extend
+DAMON for any address space by configuring the core logics with appropriate low
+level primitive implementations. If appropriate one is not provided, users can
+implement the primitives on their own.
+
+For example, physical memory, virtual memory, swap space, those for specific
+processes, NUMA nodes, files, and backing memory devices would be supportable.
+Also, if some architectures or devices support special optimized access check
+primitives, those will be easily configurable.
+
+
+Reference Implementations of Address Space Specific Primitives
+==============================================================
+
+The low level primitives for the fundamental access monitoring are defined in
+two parts:
+
+1. Identification of the monitoring target address range for the address space.
+2. Access check of specific address range in the target space.
+
+DAMON currently provides the implementation of the primitives for only the
+virtual address spaces. Below two subsections describe how it works.
+
+
+PTE Accessed-bit Based Access Check
+-----------------------------------
+
+The implementation for the virtual address space uses PTE Accessed-bit for
+basic access checks. It finds the relevant PTE Accessed bit from the address
+by walking the page table for the target task of the address. In this way, the
+implementation finds and clears the bit for next sampling target address and
+checks whether the bit set again after one sampling period. This could disturb
+other kernel subsystems using the Accessed bits, namely Idle page tracking and
+the reclaim logic. To avoid such disturbances, DAMON makes it mutually
+exclusive with Idle page tracking and uses ``PG_idle`` and ``PG_young`` page
+flags to solve the conflict with the reclaim logic, as Idle page tracking does.
+
+
+VMA-based Target Address Range Construction
+-------------------------------------------
+
+Only small parts in the super-huge virtual address space of the processes are
+mapped to the physical memory and accessed. Thus, tracking the unmapped
+address regions is just wasteful. However, because DAMON can deal with some
+level of noise using the adaptive regions adjustment mechanism, tracking every
+mapping is not strictly required but could even incur a high overhead in some
+cases. That said, too huge unmapped areas inside the monitoring target should
+be removed to not take the time for the adaptive mechanism.
+
+For the reason, this implementation converts the complex mappings to three
+distinct regions that cover every mapped area of the address space. The two
+gaps between the three regions are the two biggest unmapped areas in the given
+address space. The two biggest unmapped areas would be the gap between the
+heap and the uppermost mmap()-ed region, and the gap between the lowermost
+mmap()-ed region and the stack in most of the cases. Because these gaps are
+exceptionally huge in usual address spaces, excluding these will be sufficient
+to make a reasonable trade-off. Below shows this in detail::
+
+ <heap>
+ <BIG UNMAPPED REGION 1>
+ <uppermost mmap()-ed region>
+ (small mmap()-ed regions and munmap()-ed regions)
+ <lowermost mmap()-ed region>
+ <BIG UNMAPPED REGION 2>
+ <stack>
+
+
+Address Space Independent Core Mechanisms
+=========================================
+
+Below four sections describe each of the DAMON core mechanisms and the five
+monitoring attributes, ``sampling interval``, ``aggregation interval``,
+``regions update interval``, ``minimum number of regions``, and ``maximum
+number of regions``.
+
+
+Access Frequency Monitoring
+---------------------------
+
+The output of DAMON says what pages are how frequently accessed for a given
+duration. The resolution of the access frequency is controlled by setting
+``sampling interval`` and ``aggregation interval``. In detail, DAMON checks
+access to each page per ``sampling interval`` and aggregates the results. In
+other words, counts the number of the accesses to each page. After each
+``aggregation interval`` passes, DAMON calls callback functions that previously
+registered by users so that users can read the aggregated results and then
+clears the results. This can be described in below simple pseudo-code::
+
+ while monitoring_on:
+ for page in monitoring_target:
+ if accessed(page):
+ nr_accesses[page] += 1
+ if time() % aggregation_interval == 0:
+ for callback in user_registered_callbacks:
+ callback(monitoring_target, nr_accesses)
+ for page in monitoring_target:
+ nr_accesses[page] = 0
+ sleep(sampling interval)
+
+The monitoring overhead of this mechanism will arbitrarily increase as the
+size of the target workload grows.
+
+
+Region Based Sampling
+---------------------
+
+To avoid the unbounded increase of the overhead, DAMON groups adjacent pages
+that assumed to have the same access frequencies into a region. As long as the
+assumption (pages in a region have the same access frequencies) is kept, only
+one page in the region is required to be checked. Thus, for each ``sampling
+interval``, DAMON randomly picks one page in each region, waits for one
+``sampling interval``, checks whether the page is accessed meanwhile, and
+increases the access frequency of the region if so. Therefore, the monitoring
+overhead is controllable by setting the number of regions. DAMON allows users
+to set the minimum and the maximum number of regions for the trade-off.
+
+This scheme, however, cannot preserve the quality of the output if the
+assumption is not guaranteed.
+
+
+Adaptive Regions Adjustment
+---------------------------
+
+Even somehow the initial monitoring target regions are well constructed to
+fulfill the assumption (pages in same region have similar access frequencies),
+the data access pattern can be dynamically changed. This will result in low
+monitoring quality. To keep the assumption as much as possible, DAMON
+adaptively merges and splits each region based on their access frequency.
+
+For each ``aggregation interval``, it compares the access frequencies of
+adjacent regions and merges those if the frequency difference is small. Then,
+after it reports and clears the aggregated access frequency of each region, it
+splits each region into two or three regions if the total number of regions
+will not exceed the user-specified maximum number of regions after the split.
+
+In this way, DAMON provides its best-effort quality and minimal overhead while
+keeping the bounds users set for their trade-off.
+
+
+Dynamic Target Space Updates Handling
+-------------------------------------
+
+The monitoring target address range could dynamically changed. For example,
+virtual memory could be dynamically mapped and unmapped. Physical memory could
+be hot-plugged.
+
+As the changes could be quite frequent in some cases, DAMON checks the dynamic
+memory mapping changes and applies it to the abstracted target area only for
+each of a user-specified time interval (``regions update interval``).
diff --git a/Documentation/vm/damon/eval.rst b/Documentation/vm/damon/eval.rst
new file mode 100644
index 000000000000..4ce1a6d86036
--- /dev/null
+++ b/Documentation/vm/damon/eval.rst
@@ -0,0 +1,232 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==========
+Evaluation
+==========
+
+DAMON is lightweight. It increases system memory usage by 0.39% and slows
+target workloads down by 1.16%.
+
+DAMON is accurate and useful for memory management optimizations. An
+experimental DAMON-based operation scheme for THP, namely 'ethp', removes
+76.15% of THP memory overheads while preserving 51.25% of THP speedup. Another
+experimental DAMON-based 'proactive reclamation' implementation, namely 'prcl',
+reduces 93.38% of residential sets and 23.63% of system memory footprint while
+incurring only 1.22% runtime overhead in the best case (parsec3/freqmine).
+
+
+Setup
+=====
+
+On QEMU/KVM based virtual machines utilizing 130GB of RAM and 36 vCPUs hosted
+by AWS EC2 i3.metal instances that running a kernel that v24 DAMON patchset is
+applied, I measure runtime and consumed system memory while running various
+realistic workloads with several configurations. From each of PARSEC3 [3]_ and
+SPLASH-2X [4]_ benchmark suites I pick 12 workloads, so I use 24 workloads in
+total. I use another wrapper scripts [5]_ for convenient setup and run of the
+workloads.
+
+
+Measurement
+-----------
+
+For the measurement of the amount of consumed memory in system global scope, I
+drop caches before starting each of the workloads and monitor 'MemFree' in the
+'/proc/meminfo' file. To make results more stable, I repeat the runs 5 times
+and average results.
+
+
+Configurations
+--------------
+
+The configurations I use are as below.
+
+- orig: Linux v5.10 with 'madvise' THP policy
+- rec: 'orig' plus DAMON running with virtual memory access recording
+- prec: 'orig' plus DAMON running with physical memory access recording
+- thp: same with 'orig', but use 'always' THP policy
+- ethp: 'orig' plus a DAMON operation scheme, 'efficient THP'
+- prcl: 'orig' plus a DAMON operation scheme, 'proactive reclaim [6]_'
+
+I use 'rec' for measurement of DAMON overheads to target workloads and system
+memory. 'prec' is for physical memory monitroing and recording. It monitors
+17GB sized 'System RAM' region. The remaining configs including 'thp', 'ethp',
+and 'prcl' are for measurement of DAMON monitoring accuracy.
+
+'ethp' and 'prcl' are simple DAMON-based operation schemes developed for
+proof of concepts of DAMON. 'ethp' reduces memory space waste of THP by using
+DAMON for the decision of promotions and demotion for huge pages, while 'prcl'
+is as similar as the original work. For example, those can be implemented as
+below::
+
+ # format: <min/max size> <min/max frequency (0-100)> <min/max age> <action>
+ # ethp: Use huge pages if a region shows >=5% access rate, use regular
+ # pages if a region >=2MB shows 0 access rate for >=7 seconds
+ min max 5 max min max hugepage
+ 2M max min min 7s max nohugepage
+
+ # prcl: If a region >=4KB shows 0 access rate for >=5 seconds, page out.
+ 4K max 0 0 5s max pageout
+
+Note that these examples are designed with my only straightforward intuition
+because those are for only proof of concepts and monitoring accuracy of DAMON.
+In other words, those are not for production. For production use, those should
+be more tuned. For automation of such tuning, you can use a user space tool
+called DAMOOS [8]_. For the evaluation, we use 'ethp' as same to above
+example, but we use DAMOOS-tuned 'prcl' for each workload.
+
+The evaluation is done using the tests package for DAMON, ``damon-tests`` [7]_.
+Using it, you can do the evaluation and generate a report on your own.
+
+.. [1] "Redis latency problems troubleshooting", https://redis.io/topics/latency
+.. [2] "Disable Transparent Huge Pages (THP)",
+ https://docs.mongodb.com/manual/tutorial/transparent-huge-pages/
+.. [3] "The PARSEC Becnhmark Suite", https://parsec.cs.princeton.edu/index.htm
+.. [4] "SPLASH-2x", https://parsec.cs.princeton.edu/parsec3-doc.htm#splash2x
+.. [5] "parsec3_on_ubuntu", https://github.com/sjp38/parsec3_on_ubuntu
+.. [6] "Proactively reclaiming idle memory", https://lwn.net/Articles/787611/
+.. [7] "damon-tests", https://github.com/awslabs/damon-tests
+.. [8] "DAMOOS", https://github.com/awslabs/damoos
+
+
+Results
+=======
+
+Below two tables show the measurement results. The runtimes are in seconds
+while the memory usages are in KiB. Each configuration except 'orig' shows
+its overhead relative to 'orig' in percent within parenthesizes.::
+
+ runtime orig rec (overhead) prec (overhead) thp (overhead) ethp (overhead) prcl (overhead)
+ parsec3/blackscholes 139.658 140.168 (0.37) 139.385 (-0.20) 138.367 (-0.92) 139.279 (-0.27) 147.024 (5.27)
+ parsec3/bodytrack 123.788 124.622 (0.67) 123.636 (-0.12) 125.115 (1.07) 123.840 (0.04) 141.928 (14.65)
+ parsec3/canneal 207.491 210.318 (1.36) 217.927 (5.03) 174.287 (-16.00) 202.609 (-2.35) 225.483 (8.67)
+ parsec3/dedup 18.292 18.301 (0.05) 18.378 (0.47) 18.264 (-0.15) 18.298 (0.03) 20.541 (12.30)
+ parsec3/facesim 343.893 340.286 (-1.05) 338.217 (-1.65) 332.953 (-3.18) 333.840 (-2.92) 365.650 (6.33)
+ parsec3/fluidanimate 339.959 326.886 (-3.85) 330.286 (-2.85) 331.239 (-2.57) 326.011 (-4.10) 341.684 (0.51)
+ parsec3/freqmine 445.987 436.332 (-2.16) 435.946 (-2.25) 435.704 (-2.31) 437.595 (-1.88) 451.414 (1.22)
+ parsec3/raytrace 184.106 182.158 (-1.06) 182.056 (-1.11) 183.180 (-0.50) 183.545 (-0.30) 202.197 (9.83)
+ parsec3/streamcluster 599.990 674.091 (12.35) 617.314 (2.89) 521.864 (-13.02) 551.971 (-8.00) 696.127 (16.02)
+ parsec3/swaptions 220.462 222.637 (0.99) 220.449 (-0.01) 219.921 (-0.25) 221.607 (0.52) 223.956 (1.59)
+ parsec3/vips 87.767 88.700 (1.06) 87.461 (-0.35) 87.466 (-0.34) 87.875 (0.12) 91.768 (4.56)
+ parsec3/x264 110.843 117.856 (6.33) 113.023 (1.97) 108.665 (-1.97) 115.434 (4.14) 117.811 (6.29)
+ splash2x/barnes 131.441 129.275 (-1.65) 128.341 (-2.36) 119.317 (-9.22) 126.199 (-3.99) 147.602 (12.30)
+ splash2x/fft 59.705 58.382 (-2.22) 58.858 (-1.42) 45.949 (-23.04) 59.939 (0.39) 64.548 (8.11)
+ splash2x/lu_cb 132.552 131.604 (-0.72) 131.846 (-0.53) 132.320 (-0.18) 132.100 (-0.34) 140.289 (5.84)
+ splash2x/lu_ncb 150.215 149.670 (-0.36) 149.646 (-0.38) 148.823 (-0.93) 149.416 (-0.53) 152.338 (1.41)
+ splash2x/ocean_cp 84.033 76.405 (-9.08) 75.104 (-10.63) 73.487 (-12.55) 77.789 (-7.43) 77.380 (-7.92)
+ splash2x/ocean_ncp 153.833 154.247 (0.27) 156.227 (1.56) 106.619 (-30.69) 139.299 (-9.45) 165.030 (7.28)
+ splash2x/radiosity 143.566 143.654 (0.06) 142.426 (-0.79) 141.193 (-1.65) 141.740 (-1.27) 157.817 (9.93)
+ splash2x/radix 49.984 49.996 (0.02) 50.519 (1.07) 46.573 (-6.82) 50.724 (1.48) 50.695 (1.42)
+ splash2x/raytrace 133.238 134.337 (0.83) 134.389 (0.86) 134.833 (1.20) 131.073 (-1.62) 145.541 (9.23)
+ splash2x/volrend 121.700 120.652 (-0.86) 120.560 (-0.94) 120.629 (-0.88) 119.581 (-1.74) 129.422 (6.35)
+ splash2x/water_nsquared 370.771 375.236 (1.20) 376.829 (1.63) 355.592 (-4.09) 354.087 (-4.50) 419.606 (13.17)
+ splash2x/water_spatial 133.295 132.931 (-0.27) 132.762 (-0.40) 133.090 (-0.15) 133.809 (0.39) 153.647 (15.27)
+ total 4486.580 4538.750 (1.16) 4481.600 (-0.11) 4235.430 (-5.60) 4357.660 (-2.87) 4829.510 (7.64)
+
+
+ memused.avg orig rec (overhead) prec (overhead) thp (overhead) ethp (overhead) prcl (overhead)
+ parsec3/blackscholes 1828693.600 1834084.000 (0.29) 1823839.800 (-0.27) 1819296.600 (-0.51) 1830281.800 (0.09) 1603975.800 (-12.29)
+ parsec3/bodytrack 1424963.400 1440085.800 (1.06) 1438384.200 (0.94) 1421718.400 (-0.23) 1432834.600 (0.55) 1439283.000 (1.00)
+ parsec3/canneal 1036782.600 1052828.800 (1.55) 1050148.600 (1.29) 1035104.400 (-0.16) 1051145.400 (1.39) 1050019.400 (1.28)
+ parsec3/dedup 2511841.400 2507374.000 (-0.18) 2472450.600 (-1.57) 2523557.600 (0.47) 2508912.000 (-0.12) 2493347.200 (-0.74)
+ parsec3/facesim 537769.800 550740.800 (2.41) 548683.600 (2.03) 543547.800 (1.07) 560556.600 (4.24) 482782.600 (-10.23)
+ parsec3/fluidanimate 570268.600 585598.000 (2.69) 579837.800 (1.68) 571433.000 (0.20) 582112.800 (2.08) 470073.400 (-17.57)
+ parsec3/freqmine 982941.400 996253.200 (1.35) 993919.800 (1.12) 990531.800 (0.77) 1000994.400 (1.84) 750685.800 (-23.63)
+ parsec3/raytrace 1737446.000 1749908.800 (0.72) 1741183.800 (0.22) 1726674.800 (-0.62) 1748530.200 (0.64) 1552275.600 (-10.66)
+ parsec3/streamcluster 115857.000 155194.400 (33.95) 158272.800 (36.61) 122125.200 (5.41) 134545.600 (16.13) 133448.600 (15.18)
+ parsec3/swaptions 13694.200 28451.800 (107.76) 28464.600 (107.86) 12797.800 (-6.55) 25328.200 (84.96) 28138.400 (105.48)
+ parsec3/vips 2976126.400 3002408.600 (0.88) 3008218.800 (1.08) 2978258.600 (0.07) 2995428.600 (0.65) 2936338.600 (-1.34)
+ parsec3/x264 3233886.200 3258790.200 (0.77) 3248355.000 (0.45) 3232070.000 (-0.06) 3256360.200 (0.69) 3254707.400 (0.64)
+ splash2x/barnes 1210470.600 1211918.600 (0.12) 1204507.000 (-0.49) 1210892.800 (0.03) 1217414.800 (0.57) 944053.400 (-22.01)
+ splash2x/fft 9697440.000 9604535.600 (-0.96) 9210571.800 (-5.02) 9867368.000 (1.75) 9637571.800 (-0.62) 9804092.000 (1.10)
+ splash2x/lu_cb 510680.400 521792.600 (2.18) 517724.600 (1.38) 513500.800 (0.55) 519980.600 (1.82) 351787.000 (-31.11)
+ splash2x/lu_ncb 512896.200 529353.600 (3.21) 521248.600 (1.63) 513493.200 (0.12) 523793.400 (2.12) 418701.600 (-18.37)
+ splash2x/ocean_cp 3320800.200 3313688.400 (-0.21) 3225585.000 (-2.87) 3359032.200 (1.15) 3316591.800 (-0.13) 3304702.200 (-0.48)
+ splash2x/ocean_ncp 3915132.400 3917401.000 (0.06) 3884086.400 (-0.79) 7050398.600 (80.08) 4532528.600 (15.77) 3920395.800 (0.13)
+ splash2x/radiosity 1456908.200 1467611.800 (0.73) 1453612.600 (-0.23) 1466695.400 (0.67) 1467495.600 (0.73) 421197.600 (-71.09)
+ splash2x/radix 2345874.600 2318202.200 (-1.18) 2261499.200 (-3.60) 2438228.400 (3.94) 2373697.800 (1.19) 2336605.600 (-0.40)
+ splash2x/raytrace 43258.800 57624.200 (33.21) 55164.600 (27.52) 46204.400 (6.81) 60475.000 (39.80) 48865.400 (12.96)
+ splash2x/volrend 149615.000 163809.400 (9.49) 162115.400 (8.36) 149119.600 (-0.33) 162747.800 (8.78) 157734.600 (5.43)
+ splash2x/water_nsquared 40384.400 54848.600 (35.82) 53796.600 (33.21) 41455.800 (2.65) 53226.400 (31.80) 58260.600 (44.27)
+ splash2x/water_spatial 670580.200 680444.200 (1.47) 670020.400 (-0.08) 668262.400 (-0.35) 678552.000 (1.19) 372931.000 (-44.39)
+ total 40844300.000 41002900.000 (0.39) 40311600.000 (-1.30) 44301900.000 (8.47) 41671052.000 (2.02) 38334431.000 (-6.14)
+
+
+DAMON Overheads
+---------------
+
+In total, DAMON virtual memory access recording feature ('rec') incurs 1.16%
+runtime overhead and 0.39% memory space overhead. Even though the size of the
+monitoring target region becomes much larger with the physical memory access
+recording ('prec'), it still shows only modest amount of overhead (-0.11% for
+runtime and -1.30% for memory footprint).
+
+For a convenient test run of 'rec' and 'prec', I use a Python wrapper. The
+wrapper constantly consumes about 10-15MB of memory. This becomes a high
+memory overhead if the target workload has a small memory footprint.
+Nonetheless, the overheads are not from DAMON, but from the wrapper, and thus
+should be ignored. This fake memory overhead continues in 'ethp' and 'prcl',
+as those configurations are also using the Python wrapper.
+
+
+Efficient THP
+-------------
+
+THP 'always' enabled policy achieves 5.60% speedup but incurs 8.47% memory
+overhead. It achieves 30.69% speedup in the best case, but 80.08% memory
+overhead in the worst case. Interestingly, both the best and worst-case are
+with 'splash2x/ocean_ncp').
+
+The 2-lines implementation of data access monitoring based THP version ('ethp')
+shows 2.87% speedup and 2.02% memory overhead. In other words, 'ethp' removes
+76.15% of THP memory waste while preserving 51.25% of THP speedup in total. In
+the case of the 'splash2x/ocean_ncp', 'ethp' removes 80.30% of THP memory waste
+while preserving 30.79% of THP speedup.
+
+
+Proactive Reclamation
+---------------------
+
+As similar to the original work, I use 4G 'zram' swap device for this
+configuration. Also note that we use DAMOOS-tuned ethp schemes for each
+workload.
+
+In total, our 1 line implementation of Proactive Reclamation, 'prcl', incurred
+7.64% runtime overhead in total while achieving 6.14% system memory footprint
+reduction. Even in the worst case, the runtime overhead was only 16.02%.
+
+Nonetheless, as the memory usage is calculated with 'MemFree' in
+'/proc/meminfo', it contains the SwapCached pages. As the swapcached pages can
+be easily evicted, I also measured the residential set size of the workloads::
+
+ rss.avg orig rec (overhead) prec (overhead) thp (overhead) ethp (overhead) prcl (overhead)
+ parsec3/blackscholes 587536.800 585720.000 (-0.31) 586233.400 (-0.22) 587045.400 (-0.08) 586753.400 (-0.13) 252207.400 (-57.07)
+ parsec3/bodytrack 32302.200 32290.600 (-0.04) 32261.800 (-0.13) 32215.800 (-0.27) 32173.000 (-0.40) 6798.800 (-78.95)
+ parsec3/canneal 842370.600 841443.400 (-0.11) 844012.400 (0.19) 838074.400 (-0.51) 841700.800 (-0.08) 840804.000 (-0.19)
+ parsec3/dedup 1180414.800 1164634.600 (-1.34) 1188886.200 (0.72) 1207821.000 (2.32) 1193896.200 (1.14) 572359.200 (-51.51)
+ parsec3/facesim 311848.400 311709.800 (-0.04) 311790.800 (-0.02) 317345.800 (1.76) 315443.400 (1.15) 188488.000 (-39.56)
+ parsec3/fluidanimate 531868.000 531885.600 (0.00) 531828.800 (-0.01) 532988.000 (0.21) 532959.600 (0.21) 415153.200 (-21.94)
+ parsec3/freqmine 552491.000 552718.600 (0.04) 552807.200 (0.06) 556574.200 (0.74) 554374.600 (0.34) 36573.400 (-93.38)
+ parsec3/raytrace 879683.400 880752.200 (0.12) 879907.000 (0.03) 870631.000 (-1.03) 880952.200 (0.14) 293119.200 (-66.68)
+ parsec3/streamcluster 110991.800 110937.200 (-0.05) 110964.600 (-0.02) 115606.800 (4.16) 116199.000 (4.69) 110108.200 (-0.80)
+ parsec3/swaptions 5665.000 5718.400 (0.94) 5720.600 (0.98) 5682.200 (0.30) 5628.600 (-0.64) 3613.800 (-36.21)
+ parsec3/vips 32143.600 31823.200 (-1.00) 31912.200 (-0.72) 33164.200 (3.18) 33925.800 (5.54) 27813.600 (-13.47)
+ parsec3/x264 81534.000 81811.000 (0.34) 81708.400 (0.21) 83052.400 (1.86) 83758.800 (2.73) 81691.800 (0.19)
+ splash2x/barnes 1220515.200 1218291.200 (-0.18) 1217699.600 (-0.23) 1228551.600 (0.66) 1220669.800 (0.01) 681096.000 (-44.20)
+ splash2x/fft 9915850.400 10036461.000 (1.22) 9881242.800 (-0.35) 10334603.600 (4.22) 10006993.200 (0.92) 8975181.200 (-9.49)
+ splash2x/lu_cb 511327.200 511679.000 (0.07) 511761.600 (0.08) 511971.600 (0.13) 511711.200 (0.08) 338005.000 (-33.90)
+ splash2x/lu_ncb 511505.000 506816.800 (-0.92) 511392.800 (-0.02) 496623.000 (-2.91) 511410.200 (-0.02) 404734.000 (-20.87)
+ splash2x/ocean_cp 3398834.000 3405017.800 (0.18) 3415287.800 (0.48) 3443604.600 (1.32) 3416264.200 (0.51) 3387134.000 (-0.34)
+ splash2x/ocean_ncp 3947092.800 3939805.400 (-0.18) 3952311.600 (0.13) 7165858.800 (81.55) 4610075.000 (16.80) 3944753.400 (-0.06)
+ splash2x/radiosity 1475024.000 1474053.200 (-0.07) 1475032.400 (0.00) 1483718.800 (0.59) 1475919.600 (0.06) 99637.200 (-93.25)
+ splash2x/radix 2431302.200 2416928.600 (-0.59) 2455596.800 (1.00) 2568526.400 (5.64) 2479966.800 (2.00) 2437406.600 (0.25)
+ splash2x/raytrace 23274.400 23278.400 (0.02) 23287.200 (0.05) 28828.000 (23.86) 27800.200 (19.45) 5667.000 (-75.65)
+ splash2x/volrend 44106.800 44151.400 (0.10) 44186.000 (0.18) 45200.400 (2.48) 44751.200 (1.46) 16912.000 (-61.66)
+ splash2x/water_nsquared 29427.200 29425.600 (-0.01) 29402.400 (-0.08) 28055.400 (-4.66) 28572.400 (-2.90) 13207.800 (-55.12)
+ splash2x/water_spatial 664312.200 664095.600 (-0.03) 663025.200 (-0.19) 664100.600 (-0.03) 663597.400 (-0.11) 261214.200 (-60.68)
+ total 29321300.000 29401500.000 (0.27) 29338300.000 (0.06) 33179900.000 (13.16) 30175600.000 (2.91) 23393600.000 (-20.22)
+
+In total, 20.22% of residential sets were reduced.
+
+With parsec3/freqmine, 'prcl' reduced 93.38% of residential sets and 23.63% of
+system memory usage while incurring only 1.22% runtime overhead.
diff --git a/Documentation/vm/damon/faq.rst b/Documentation/vm/damon/faq.rst
new file mode 100644
index 000000000000..088128bbf22b
--- /dev/null
+++ b/Documentation/vm/damon/faq.rst
@@ -0,0 +1,58 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==========================
+Frequently Asked Questions
+==========================
+
+Why a new subsystem, instead of extending perf or other user space tools?
+=========================================================================
+
+First, because it needs to be lightweight as much as possible so that it can be
+used online, any unnecessary overhead such as kernel - user space context
+switching cost should be avoided. Second, DAMON aims to be used by other
+programs including the kernel. Therefore, having a dependency on specific
+tools like perf is not desirable. These are the two biggest reasons why DAMON
+is implemented in the kernel space.
+
+
+Can 'idle pages tracking' or 'perf mem' substitute DAMON?
+=========================================================
+
+Idle page tracking is a low level primitive for access check of the physical
+address space. 'perf mem' is similar, though it can use sampling to minimize
+the overhead. On the other hand, DAMON is a higher-level framework for the
+monitoring of various address spaces. It is focused on memory management
+optimization and provides sophisticated accuracy/overhead handling mechanisms.
+Therefore, 'idle pages tracking' and 'perf mem' could provide a subset of
+DAMON's output, but cannot substitute DAMON.
+
+
+How can I optimize my system's memory management using DAMON?
+=============================================================
+
+Because there are several ways for the DAMON-based optimizations, we wrote a
+separate document, :doc:`/admin-guide/mm/damon/guide`. Please refer to that.
+
+
+Does DAMON support virtual memory only?
+=======================================
+
+No. The core of the DAMON is address space independent. The address space
+specific low level primitive parts including monitoring target regions
+constructions and actual access checks can be implemented and configured on the
+DAMON core by the users. In this way, DAMON users can monitor any address
+space with any access check technique.
+
+Nonetheless, DAMON provides vma tracking and PTE Accessed bit check based
+implementations of the address space dependent functions for the virtual memory
+by default, for a reference and convenient use. In near future, we will
+provide those for physical memory address space.
+
+
+Can I simply monitor page granularity?
+======================================
+
+Yes. You can do so by setting the ``min_nr_regions`` attribute higher than the
+working set size divided by the page size. Because the monitoring target
+regions size is forced to be ``>=page size``, the region split will make no
+effect.
diff --git a/Documentation/vm/damon/index.rst b/Documentation/vm/damon/index.rst
new file mode 100644
index 000000000000..17dca3c12aad
--- /dev/null
+++ b/Documentation/vm/damon/index.rst
@@ -0,0 +1,31 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==========================
+DAMON: Data Access MONitor
+==========================
+
+DAMON is a data access monitoring framework subsystem for the Linux kernel.
+The core mechanisms of DAMON (refer to :doc:`design` for the detail) make it
+
+ - *accurate* (the monitoring output is useful enough for DRAM level memory
+ management; It might not appropriate for CPU Cache levels, though),
+ - *light-weight* (the monitoring overhead is low enough to be applied online),
+ and
+ - *scalable* (the upper-bound of the overhead is in constant range regardless
+ of the size of target workloads).
+
+Using this framework, therefore, the kernel's memory management mechanisms can
+make advanced decisions. Experimental memory management optimization works
+that incurring high data accesses monitoring overhead could implemented again.
+In user space, meanwhile, users who have some special workloads can write
+personalized applications for better understanding and optimizations of their
+workloads and systems.
+
+.. toctree::
+ :maxdepth: 2
+
+ faq
+ design
+ eval
+ api
+ plans
diff --git a/Documentation/vm/index.rst b/Documentation/vm/index.rst
index eff5fbd492d0..b51f0d8992f8 100644
--- a/Documentation/vm/index.rst
+++ b/Documentation/vm/index.rst
@@ -32,6 +32,7 @@ descriptions of data structures and algorithms.
arch_pgtable_helpers
balance
cleancache
+ damon/index
free_page_reporting
frontswap
highmem
--
2.17.1
From: SeongJae Park <[email protected]>
This commit adds a simple user space tests for DAMON. The tests are
using kselftest framework.
Signed-off-by: SeongJae Park <[email protected]>
---
tools/testing/selftests/damon/Makefile | 7 ++
.../selftests/damon/_chk_dependency.sh | 28 ++++++
.../testing/selftests/damon/debugfs_attrs.sh | 98 +++++++++++++++++++
3 files changed, 133 insertions(+)
create mode 100644 tools/testing/selftests/damon/Makefile
create mode 100644 tools/testing/selftests/damon/_chk_dependency.sh
create mode 100755 tools/testing/selftests/damon/debugfs_attrs.sh
diff --git a/tools/testing/selftests/damon/Makefile b/tools/testing/selftests/damon/Makefile
new file mode 100644
index 000000000000..8a3f2cd9fec0
--- /dev/null
+++ b/tools/testing/selftests/damon/Makefile
@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0
+# Makefile for damon selftests
+
+TEST_FILES = _chk_dependency.sh
+TEST_PROGS = debugfs_attrs.sh
+
+include ../lib.mk
diff --git a/tools/testing/selftests/damon/_chk_dependency.sh b/tools/testing/selftests/damon/_chk_dependency.sh
new file mode 100644
index 000000000000..e090836c2bf7
--- /dev/null
+++ b/tools/testing/selftests/damon/_chk_dependency.sh
@@ -0,0 +1,28 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+
+DBGFS=/sys/kernel/debug/damon
+
+if [ $EUID -ne 0 ];
+then
+ echo "Run as root"
+ exit $ksft_skip
+fi
+
+if [ ! -d $DBGFS ]
+then
+ echo "$DBGFS not found"
+ exit $ksft_skip
+fi
+
+for f in attrs target_ids monitor_on
+do
+ if [ ! -f "$DBGFS/$f" ]
+ then
+ echo "$f not found"
+ exit 1
+ fi
+done
diff --git a/tools/testing/selftests/damon/debugfs_attrs.sh b/tools/testing/selftests/damon/debugfs_attrs.sh
new file mode 100755
index 000000000000..4a8ab4910ee4
--- /dev/null
+++ b/tools/testing/selftests/damon/debugfs_attrs.sh
@@ -0,0 +1,98 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+source ./_chk_dependency.sh
+
+# Test attrs file
+file="$DBGFS/attrs"
+
+ORIG_CONTENT=$(cat $file)
+
+echo 1 2 3 4 5 > $file
+if [ $? -ne 0 ]
+then
+ echo "$file write failed"
+ echo $ORIG_CONTENT > $file
+ exit 1
+fi
+
+echo 1 2 3 4 > $file
+if [ $? -eq 0 ]
+then
+ echo "$file write success (should failed)"
+ echo $ORIG_CONTENT > $file
+ exit 1
+fi
+
+CONTENT=$(cat $file)
+if [ "$CONTENT" != "1 2 3 4 5" ]
+then
+ echo "$file not written"
+ echo $ORIG_CONTENT > $file
+ exit 1
+fi
+
+echo $ORIG_CONTENT > $file
+
+# Test target_ids file
+file="$DBGFS/target_ids"
+
+ORIG_CONTENT=$(cat $file)
+
+echo "1 2 3 4" > $file
+if [ $? -ne 0 ]
+then
+ echo "$file write fail"
+ echo $ORIG_CONTENT > $file
+ exit 1
+fi
+
+echo "1 2 abc 4" > $file
+if [ $? -ne 0 ]
+then
+ echo "$file write fail"
+ echo $ORIG_CONTENT > $file
+ exit 1
+fi
+
+CONTENT=$(cat $file)
+if [ "$CONTENT" != "1 2" ]
+then
+ echo "$file not written"
+ echo $ORIG_CONTENT > $file
+ exit 1
+fi
+
+echo abc 2 3 > $file
+if [ $? -ne 0 ]
+then
+ echo "$file wrong value write fail"
+ echo $ORIG_CONTENT > $file
+ exit 1
+fi
+
+if [ ! -z "$(cat $file)" ]
+then
+ echo "$file not cleared"
+ echo $ORIG_CONTENT > $file
+ exit 1
+fi
+
+echo > $file
+if [ $? -ne 0 ]
+then
+ echo "$file init fail"
+ echo $ORIG_CONTENT > $file
+ exit 1
+fi
+
+if [ ! -z "$(cat $file)" ]
+then
+ echo "$file not initialized"
+ echo $ORIG_CONTENT > $file
+ exit 1
+fi
+
+echo $ORIG_CONTENT > $file
+
+echo "PASS"
--
2.17.1
From: SeongJae Park <[email protected]>
This commit updates MAINTAINERS file for DAMON related files.
Signed-off-by: SeongJae Park <[email protected]>
---
MAINTAINERS | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/MAINTAINERS b/MAINTAINERS
index ad650102f950..0df746019eb9 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5003,6 +5003,18 @@ F: net/ax25/ax25_out.c
F: net/ax25/ax25_timer.c
F: net/ax25/sysctl_net_ax25.c
+DATA ACCESS MONITOR
+M: SeongJae Park <[email protected]>
+L: [email protected]
+S: Maintained
+F: Documentation/admin-guide/mm/damon/*
+F: Documentation/vm/damon/*
+F: include/linux/damon.h
+F: include/trace/events/damon.h
+F: mm/damon/*
+F: tools/damon/*
+F: tools/testing/selftests/damon/*
+
DAVICOM FAST ETHERNET (DMFE) NETWORK DRIVER
L: [email protected]
S: Orphan
--
2.17.1
On Thu, Apr 08, 2021 at 01:48:48PM +0000, SeongJae Park wrote:
> +static int dbgfs_fill_ctx_dir(struct dentry *dir, struct damon_ctx *ctx)
> +{
> + const char * const file_names[] = {"attrs", "target_ids"};
> + const struct file_operations *fops[] = {&attrs_fops, &target_ids_fops};
> + int i;
> +
> + for (i = 0; i < ARRAY_SIZE(file_names); i++)
> + debugfs_create_file(file_names[i], 0600, dir, ctx, fops[i]);
> +
> + return 0;
> +}
Why do you have a function that can only return 0, actually return
something? It should be void, right?
thanks,
greg k-h
From: SeongJae Park <[email protected]>
On Sat, 10 Apr 2021 10:55:01 +0200 Greg KH <[email protected]> wrote:
> On Thu, Apr 08, 2021 at 01:48:48PM +0000, SeongJae Park wrote:
> > +static int dbgfs_fill_ctx_dir(struct dentry *dir, struct damon_ctx *ctx)
> > +{
> > + const char * const file_names[] = {"attrs", "target_ids"};
> > + const struct file_operations *fops[] = {&attrs_fops, &target_ids_fops};
> > + int i;
> > +
> > + for (i = 0; i < ARRAY_SIZE(file_names); i++)
> > + debugfs_create_file(file_names[i], 0600, dir, ctx, fops[i]);
> > +
> > + return 0;
> > +}
>
> Why do you have a function that can only return 0, actually return
> something? It should be void, right?
You're right, I will make it return void in the next spin.
Thanks,
SeongJae Park
>
> thanks,
>
> greg k-h
>
From: SeongJae Park <[email protected]>
On Thu, 8 Apr 2021 13:48:48 +0000 SeongJae Park <[email protected]> wrote:
> From: SeongJae Park <[email protected]>
>
> DAMON is designed to be used by kernel space code such as the memory
> management subsystems, and therefore it provides only kernel space API.
> That said, letting the user space control DAMON could provide some
> benefits to them. For example, it will allow user space to analyze
> their specific workloads and make their own special optimizations.
>
> For such cases, this commit implements a simple DAMON application kernel
> module, namely 'damon-dbgfs', which merely wraps the DAMON api and
> exports those to the user space via the debugfs.
>
[...]
> +/*
> + * Functions for the initialization
> + */
> +
> +static int __init damon_dbgfs_init(void)
> +{
> + int rc;
> +
> + dbgfs_ctxs = kmalloc(sizeof(*dbgfs_ctxs), GFP_KERNEL);
> + if (!dbgfs_ctxs) {
> + pr_err("%s: dbgfs ctxs alloc failed\n", __func__);
> + return -ENOMEM;
> + }
> + dbgfs_ctxs[0] = dbgfs_new_ctx();
> + if (!dbgfs_ctxs[0]) {
> + pr_err("%s: dbgfs ctx alloc failed\n", __func__);
> + return -ENOMEM;
My colleague, Stefan found 'dbgfs_ctxs' is not freed here. Similar in below
'__damon_dbgfs_init()' failure handling. I will fix these in the next version.
Reported-by: Stefan Nuernberger <[email protected]>
Thanks,
SeongJae Park
> + }
> + dbgfs_nr_ctxs = 1;
> +
> + rc = __damon_dbgfs_init();
> + if (rc)
> + pr_err("%s: dbgfs init failed\n", __func__);
> +
> + return rc;
> +}
> +
> +module_init(damon_dbgfs_init);
> --
> 2.17.1
>
