When a memory device, such as CXL1.1 type3 memory, is emulated as
normal memory (E820_TYPE_RAM), the memory device is indistinguishable from
normal DRAM in terms of memory tiering with the current implementation.
The current memory tiering assigns all detected normal memory nodes to
the same DRAM tier. This results in normal memory devices with different
attributions being unable to be assigned to the correct memory tier,
leading to the inability to migrate pages between different
types of memory.
https://lore.kernel.org/linux-mm/PH0PR08MB7955E9F08CCB64F23963B5C3A860A@PH0PR08MB7955.namprd08.prod.outlook.com/T/
This patchset automatically resolves the issues. It delays the
initialization of memory tiers for CPUless NUMA nodes until they obtain
HMAT information and after all devices are initialized at boot time,
eliminating the need for user intervention. If no HMAT is specified,
it falls back to using `default_dram_type`.
Example usecase:
We have CXL memory on the host, and we create VMs with a new system memory
device backed by host CXL memory. We inject CXL memory performance
attributes through QEMU, and the guest now sees memory nodes with
performance attributes in HMAT. With this change, we enable the
guest kernel to construct the correct memory tiering for the memory nodes.
- v11:
Thanks to comments from Jonathan,
* Replace `mutex_lock()` with `guard(mutex)()`
* Reorder some modifications within the patchset
* Rewrite the code for improved readability and fixing alignment issues
* Pass all strict rules in checkpatch.pl
- v10:
Thanks to Andrew's and SeongJae's comments,
* Address kunit compilation errors
* Resolve the bug of not returning the correct error code in
`mt_perf_to_adistance`
* https://lore.kernel.org/lkml/[email protected]/T/#u
-v9:
* Address corner cases in `memory_tier_late_init`. Thank Ying's comments.
* https://lore.kernel.org/lkml/[email protected]/T/#u
-v8:
* Fix email format
* https://lore.kernel.org/lkml/[email protected]/T/#u
-v7:
* Add Reviewed-by: "Huang, Ying" <[email protected]>
-v6:
Thanks to Ying's comments,
* Move `default_dram_perf_lock` to the function's beginning for clarity
* Fix double unlocking at v5
* https://lore.kernel.org/lkml/[email protected]/T/#u
-v5:
Thanks to Ying's comments,
* Add comments about what is protected by `default_dram_perf_lock`
* Fix an uninitialized pointer mtype
* Slightly shorten the time holding `default_dram_perf_lock`
* Fix a deadlock bug in `mt_perf_to_adistance`
* https://lore.kernel.org/lkml/[email protected]/T/#u
-v4:
Thanks to Ying's comments,
* Remove redundant code
* Reorganize patches accordingly
* https://lore.kernel.org/lkml/[email protected]/T/#u
-v3:
Thanks to Ying's comments,
* Make the newly added code independent of HMAT
* Upgrade set_node_memory_tier to support more cases
* Put all non-driver-initialized memory types into default_memory_types
instead of using hmat_memory_types
* find_alloc_memory_type -> mt_find_alloc_memory_type
* https://lore.kernel.org/lkml/[email protected]/T/#u
-v2:
Thanks to Ying's comments,
* Rewrite cover letter & patch description
* Rename functions, don't use _hmat
* Abstract common functions into find_alloc_memory_type()
* Use the expected way to use set_node_memory_tier instead of modifying it
* https://lore.kernel.org/lkml/[email protected]/T/#u
-v1:
* https://lore.kernel.org/lkml/[email protected]/T/#u
Ho-Ren (Jack) Chuang (2):
memory tier: dax/kmem: introduce an abstract layer for finding,
allocating, and putting memory types
memory tier: create CPUless memory tiers after obtaining HMAT info
drivers/dax/kmem.c | 30 ++-------
include/linux/memory-tiers.h | 13 ++++
mm/memory-tiers.c | 123 ++++++++++++++++++++++++++++-------
3 files changed, 116 insertions(+), 50 deletions(-)
--
Ho-Ren (Jack) Chuang
Since different memory devices require finding, allocating, and putting
memory types, these common steps are abstracted in this patch,
enhancing the scalability and conciseness of the code.
Signed-off-by: Ho-Ren (Jack) Chuang <[email protected]>
Reviewed-by: "Huang, Ying" <[email protected]>
---
drivers/dax/kmem.c | 30 ++++--------------------------
include/linux/memory-tiers.h | 13 +++++++++++++
mm/memory-tiers.c | 29 +++++++++++++++++++++++++++++
3 files changed, 46 insertions(+), 26 deletions(-)
diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
index 42ee360cf4e3..4fe9d040e375 100644
--- a/drivers/dax/kmem.c
+++ b/drivers/dax/kmem.c
@@ -55,36 +55,14 @@ static LIST_HEAD(kmem_memory_types);
static struct memory_dev_type *kmem_find_alloc_memory_type(int adist)
{
- bool found = false;
- struct memory_dev_type *mtype;
-
- mutex_lock(&kmem_memory_type_lock);
- list_for_each_entry(mtype, &kmem_memory_types, list) {
- if (mtype->adistance == adist) {
- found = true;
- break;
- }
- }
- if (!found) {
- mtype = alloc_memory_type(adist);
- if (!IS_ERR(mtype))
- list_add(&mtype->list, &kmem_memory_types);
- }
- mutex_unlock(&kmem_memory_type_lock);
-
- return mtype;
+ guard(mutex)(&kmem_memory_type_lock);
+ return mt_find_alloc_memory_type(adist, &kmem_memory_types);
}
static void kmem_put_memory_types(void)
{
- struct memory_dev_type *mtype, *mtn;
-
- mutex_lock(&kmem_memory_type_lock);
- list_for_each_entry_safe(mtype, mtn, &kmem_memory_types, list) {
- list_del(&mtype->list);
- put_memory_type(mtype);
- }
- mutex_unlock(&kmem_memory_type_lock);
+ guard(mutex)(&kmem_memory_type_lock);
+ mt_put_memory_types(&kmem_memory_types);
}
static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
index 69e781900082..0d70788558f4 100644
--- a/include/linux/memory-tiers.h
+++ b/include/linux/memory-tiers.h
@@ -48,6 +48,9 @@ int mt_calc_adistance(int node, int *adist);
int mt_set_default_dram_perf(int nid, struct access_coordinate *perf,
const char *source);
int mt_perf_to_adistance(struct access_coordinate *perf, int *adist);
+struct memory_dev_type *mt_find_alloc_memory_type(int adist,
+ struct list_head *memory_types);
+void mt_put_memory_types(struct list_head *memory_types);
#ifdef CONFIG_MIGRATION
int next_demotion_node(int node);
void node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *targets);
@@ -136,5 +139,15 @@ static inline int mt_perf_to_adistance(struct access_coordinate *perf, int *adis
{
return -EIO;
}
+
+static inline struct memory_dev_type *mt_find_alloc_memory_type(int adist,
+ struct list_head *memory_types)
+{
+ return NULL;
+}
+
+static inline void mt_put_memory_types(struct list_head *memory_types)
+{
+}
#endif /* CONFIG_NUMA */
#endif /* _LINUX_MEMORY_TIERS_H */
diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
index 0537664620e5..516b144fd45a 100644
--- a/mm/memory-tiers.c
+++ b/mm/memory-tiers.c
@@ -623,6 +623,35 @@ void clear_node_memory_type(int node, struct memory_dev_type *memtype)
}
EXPORT_SYMBOL_GPL(clear_node_memory_type);
+struct memory_dev_type *mt_find_alloc_memory_type(int adist, struct list_head *memory_types)
+{
+ struct memory_dev_type *mtype;
+
+ list_for_each_entry(mtype, memory_types, list)
+ if (mtype->adistance == adist)
+ return mtype;
+
+ mtype = alloc_memory_type(adist);
+ if (IS_ERR(mtype))
+ return mtype;
+
+ list_add(&mtype->list, memory_types);
+
+ return mtype;
+}
+EXPORT_SYMBOL_GPL(mt_find_alloc_memory_type);
+
+void mt_put_memory_types(struct list_head *memory_types)
+{
+ struct memory_dev_type *mtype, *mtn;
+
+ list_for_each_entry_safe(mtype, mtn, memory_types, list) {
+ list_del(&mtype->list);
+ put_memory_type(mtype);
+ }
+}
+EXPORT_SYMBOL_GPL(mt_put_memory_types);
+
static void dump_hmem_attrs(struct access_coordinate *coord, const char *prefix)
{
pr_info(
--
Ho-Ren (Jack) Chuang
The current implementation treats emulated memory devices, such as
CXL1.1 type3 memory, as normal DRAM when they are emulated as normal memory
(E820_TYPE_RAM). However, these emulated devices have different
characteristics than traditional DRAM, making it important to
distinguish them. Thus, we modify the tiered memory initialization process
to introduce a delay specifically for CPUless NUMA nodes. This delay
ensures that the memory tier initialization for these nodes is deferred
until HMAT information is obtained during the boot process. Finally,
demotion tables are recalculated at the end.
* late_initcall(memory_tier_late_init);
Some device drivers may have initialized memory tiers between
`memory_tier_init()` and `memory_tier_late_init()`, potentially bringing
online memory nodes and configuring memory tiers. They should be excluded
in the late init.
* Handle cases where there is no HMAT when creating memory tiers
There is a scenario where a CPUless node does not provide HMAT information.
If no HMAT is specified, it falls back to using the default DRAM tier.
* Introduce another new lock `default_dram_perf_lock` for adist calculation
In the current implementation, iterating through CPUlist nodes requires
holding the `memory_tier_lock`. However, `mt_calc_adistance()` will end up
trying to acquire the same lock, leading to a potential deadlock.
Therefore, we propose introducing a standalone `default_dram_perf_lock` to
protect `default_dram_perf_*`. This approach not only avoids deadlock
but also prevents holding a large lock simultaneously.
* Upgrade `set_node_memory_tier` to support additional cases, including
default DRAM, late CPUless, and hot-plugged initializations.
To cover hot-plugged memory nodes, `mt_calc_adistance()` and
`mt_find_alloc_memory_type()` are moved into `set_node_memory_tier()` to
handle cases where memtype is not initialized and where HMAT information is
available.
* Introduce `default_memory_types` for those memory types that are not
initialized by device drivers.
Because late initialized memory and default DRAM memory need to be managed,
a default memory type is created for storing all memory types that are
not initialized by device drivers and as a fallback.
Signed-off-by: Ho-Ren (Jack) Chuang <[email protected]>
Signed-off-by: Hao Xiang <[email protected]>
Reviewed-by: "Huang, Ying" <[email protected]>
---
mm/memory-tiers.c | 94 +++++++++++++++++++++++++++++++++++------------
1 file changed, 70 insertions(+), 24 deletions(-)
diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
index 516b144fd45a..6632102bd5c9 100644
--- a/mm/memory-tiers.c
+++ b/mm/memory-tiers.c
@@ -36,6 +36,11 @@ struct node_memory_type_map {
static DEFINE_MUTEX(memory_tier_lock);
static LIST_HEAD(memory_tiers);
+/*
+ * The list is used to store all memory types that are not created
+ * by a device driver.
+ */
+static LIST_HEAD(default_memory_types);
static struct node_memory_type_map node_memory_types[MAX_NUMNODES];
struct memory_dev_type *default_dram_type;
@@ -108,6 +113,8 @@ static struct demotion_nodes *node_demotion __read_mostly;
static BLOCKING_NOTIFIER_HEAD(mt_adistance_algorithms);
+/* The lock is used to protect `default_dram_perf*` info and nid. */
+static DEFINE_MUTEX(default_dram_perf_lock);
static bool default_dram_perf_error;
static struct access_coordinate default_dram_perf;
static int default_dram_perf_ref_nid = NUMA_NO_NODE;
@@ -505,7 +512,8 @@ static inline void __init_node_memory_type(int node, struct memory_dev_type *mem
static struct memory_tier *set_node_memory_tier(int node)
{
struct memory_tier *memtier;
- struct memory_dev_type *memtype;
+ struct memory_dev_type *memtype = default_dram_type;
+ int adist = MEMTIER_ADISTANCE_DRAM;
pg_data_t *pgdat = NODE_DATA(node);
@@ -514,7 +522,16 @@ static struct memory_tier *set_node_memory_tier(int node)
if (!node_state(node, N_MEMORY))
return ERR_PTR(-EINVAL);
- __init_node_memory_type(node, default_dram_type);
+ mt_calc_adistance(node, &adist);
+ if (!node_memory_types[node].memtype) {
+ memtype = mt_find_alloc_memory_type(adist, &default_memory_types);
+ if (IS_ERR(memtype)) {
+ memtype = default_dram_type;
+ pr_info("Failed to allocate a memory type. Fall back.\n");
+ }
+ }
+
+ __init_node_memory_type(node, memtype);
memtype = node_memory_types[node].memtype;
node_set(node, memtype->nodes);
@@ -652,6 +669,35 @@ void mt_put_memory_types(struct list_head *memory_types)
}
EXPORT_SYMBOL_GPL(mt_put_memory_types);
+/*
+ * This is invoked via `late_initcall()` to initialize memory tiers for
+ * CPU-less memory nodes after driver initialization, which is
+ * expected to provide `adistance` algorithms.
+ */
+static int __init memory_tier_late_init(void)
+{
+ int nid;
+
+ guard(mutex)(&memory_tier_lock);
+ for_each_node_state(nid, N_MEMORY) {
+ /*
+ * Some device drivers may have initialized memory tiers
+ * between `memory_tier_init()` and `memory_tier_late_init()`,
+ * potentially bringing online memory nodes and
+ * configuring memory tiers. Exclude them here.
+ */
+ if (node_memory_types[nid].memtype)
+ continue;
+
+ set_node_memory_tier(nid);
+ }
+
+ establish_demotion_targets();
+
+ return 0;
+}
+late_initcall(memory_tier_late_init);
+
static void dump_hmem_attrs(struct access_coordinate *coord, const char *prefix)
{
pr_info(
@@ -663,25 +709,19 @@ static void dump_hmem_attrs(struct access_coordinate *coord, const char *prefix)
int mt_set_default_dram_perf(int nid, struct access_coordinate *perf,
const char *source)
{
- int rc = 0;
-
- mutex_lock(&memory_tier_lock);
- if (default_dram_perf_error) {
- rc = -EIO;
- goto out;
- }
+ guard(mutex)(&default_dram_perf_lock);
+ if (default_dram_perf_error)
+ return -EIO;
if (perf->read_latency + perf->write_latency == 0 ||
- perf->read_bandwidth + perf->write_bandwidth == 0) {
- rc = -EINVAL;
- goto out;
- }
+ perf->read_bandwidth + perf->write_bandwidth == 0)
+ return -EINVAL;
if (default_dram_perf_ref_nid == NUMA_NO_NODE) {
default_dram_perf = *perf;
default_dram_perf_ref_nid = nid;
default_dram_perf_ref_source = kstrdup(source, GFP_KERNEL);
- goto out;
+ return 0;
}
/*
@@ -709,27 +749,25 @@ int mt_set_default_dram_perf(int nid, struct access_coordinate *perf,
pr_info(
" disable default DRAM node performance based abstract distance algorithm.\n");
default_dram_perf_error = true;
- rc = -EINVAL;
+ return -EINVAL;
}
-out:
- mutex_unlock(&memory_tier_lock);
- return rc;
+ return 0;
}
int mt_perf_to_adistance(struct access_coordinate *perf, int *adist)
{
+ guard(mutex)(&default_dram_perf_lock);
if (default_dram_perf_error)
return -EIO;
- if (default_dram_perf_ref_nid == NUMA_NO_NODE)
- return -ENOENT;
-
if (perf->read_latency + perf->write_latency == 0 ||
perf->read_bandwidth + perf->write_bandwidth == 0)
return -EINVAL;
- mutex_lock(&memory_tier_lock);
+ if (default_dram_perf_ref_nid == NUMA_NO_NODE)
+ return -ENOENT;
+
/*
* The abstract distance of a memory node is in direct proportion to
* its memory latency (read + write) and inversely proportional to its
@@ -742,7 +780,6 @@ int mt_perf_to_adistance(struct access_coordinate *perf, int *adist)
(default_dram_perf.read_latency + default_dram_perf.write_latency) *
(default_dram_perf.read_bandwidth + default_dram_perf.write_bandwidth) /
(perf->read_bandwidth + perf->write_bandwidth);
- mutex_unlock(&memory_tier_lock);
return 0;
}
@@ -855,7 +892,8 @@ static int __init memory_tier_init(void)
* For now we can have 4 faster memory tiers with smaller adistance
* than default DRAM tier.
*/
- default_dram_type = alloc_memory_type(MEMTIER_ADISTANCE_DRAM);
+ default_dram_type = mt_find_alloc_memory_type(MEMTIER_ADISTANCE_DRAM,
+ &default_memory_types);
if (IS_ERR(default_dram_type))
panic("%s() failed to allocate default DRAM tier\n", __func__);
@@ -865,6 +903,14 @@ static int __init memory_tier_init(void)
* types assigned.
*/
for_each_node_state(node, N_MEMORY) {
+ if (!node_state(node, N_CPU))
+ /*
+ * Defer memory tier initialization on
+ * CPUless numa nodes. These will be initialized
+ * after firmware and devices are initialized.
+ */
+ continue;
+
memtier = set_node_memory_tier(node);
if (IS_ERR(memtier))
/*
--
Ho-Ren (Jack) Chuang
On Fri, Apr 5, 2024 at 7:03 AM Jonathan Cameron
<[email protected]> wrote:
>
> On Fri, 5 Apr 2024 00:07:06 +0000
> "Ho-Ren (Jack) Chuang" <[email protected]> wrote:
>
> > The current implementation treats emulated memory devices, such as
> > CXL1.1 type3 memory, as normal DRAM when they are emulated as normal memory
> > (E820_TYPE_RAM). However, these emulated devices have different
> > characteristics than traditional DRAM, making it important to
> > distinguish them. Thus, we modify the tiered memory initialization process
> > to introduce a delay specifically for CPUless NUMA nodes. This delay
> > ensures that the memory tier initialization for these nodes is deferred
> > until HMAT information is obtained during the boot process. Finally,
> > demotion tables are recalculated at the end.
> >
> > * late_initcall(memory_tier_late_init);
> > Some device drivers may have initialized memory tiers between
> > `memory_tier_init()` and `memory_tier_late_init()`, potentially bringing
> > online memory nodes and configuring memory tiers. They should be excluded
> > in the late init.
> >
> > * Handle cases where there is no HMAT when creating memory tiers
> > There is a scenario where a CPUless node does not provide HMAT information.
> > If no HMAT is specified, it falls back to using the default DRAM tier.
> >
> > * Introduce another new lock `default_dram_perf_lock` for adist calculation
> > In the current implementation, iterating through CPUlist nodes requires
> > holding the `memory_tier_lock`. However, `mt_calc_adistance()` will end up
> > trying to acquire the same lock, leading to a potential deadlock.
> > Therefore, we propose introducing a standalone `default_dram_perf_lock` to
> > protect `default_dram_perf_*`. This approach not only avoids deadlock
> > but also prevents holding a large lock simultaneously.
> >
> > * Upgrade `set_node_memory_tier` to support additional cases, including
> > default DRAM, late CPUless, and hot-plugged initializations.
> > To cover hot-plugged memory nodes, `mt_calc_adistance()` and
> > `mt_find_alloc_memory_type()` are moved into `set_node_memory_tier()` to
> > handle cases where memtype is not initialized and where HMAT information is
> > available.
> >
> > * Introduce `default_memory_types` for those memory types that are not
> > initialized by device drivers.
> > Because late initialized memory and default DRAM memory need to be managed,
> > a default memory type is created for storing all memory types that are
> > not initialized by device drivers and as a fallback.
> >
> > Signed-off-by: Ho-Ren (Jack) Chuang <[email protected]>
> > Signed-off-by: Hao Xiang <[email protected]>
> > Reviewed-by: "Huang, Ying" <[email protected]>
>
> Hi - one remaining question. Why can't we delay init for all nodes
> to either drivers or your fallback late_initcall code.
> It would be nice to reduce possible code paths.
I try not to change too much of the existing code structure in
this patchset.
To me, postponing/moving all memory tier registrations to
late_initcall() is another possible action item for the next patchset.
After tier_mem(), hmat_init() is called, which requires registering
`default_dram_type` info. This is when `default_dram_type` is needed.
However, it is indeed possible to postpone the latter part,
set_node_memory_tier(), to `late_init(). So, memory_tier_init() can
indeed be split into two parts, and the latter part can be moved to
late_initcall() to be processed together.
Doing this all memory-type drivers have to call late_initcall() to
register a memory tier. I’m not sure how many they are?
What do you guys think?
>
> Jonathan
>
>
> > ---
> > mm/memory-tiers.c | 94 +++++++++++++++++++++++++++++++++++------------
> > 1 file changed, 70 insertions(+), 24 deletions(-)
> >
> > diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
> > index 516b144fd45a..6632102bd5c9 100644
> > --- a/mm/memory-tiers.c
> > +++ b/mm/memory-tiers.c
>
>
>
> > @@ -855,7 +892,8 @@ static int __init memory_tier_init(void)
> > * For now we can have 4 faster memory tiers with smaller adistance
> > * than default DRAM tier.
> > */
> > - default_dram_type = alloc_memory_type(MEMTIER_ADISTANCE_DRAM);
> > + default_dram_type = mt_find_alloc_memory_type(MEMTIER_ADISTANCE_DRAM,
> > + &default_memory_types);
> > if (IS_ERR(default_dram_type))
> > panic("%s() failed to allocate default DRAM tier\n", __func__);
> >
> > @@ -865,6 +903,14 @@ static int __init memory_tier_init(void)
> > * types assigned.
> > */
> > for_each_node_state(node, N_MEMORY) {
> > + if (!node_state(node, N_CPU))
> > + /*
> > + * Defer memory tier initialization on
> > + * CPUless numa nodes. These will be initialized
> > + * after firmware and devices are initialized.
>
> Could the comment also say why we can't defer them all?
>
> (In an odd coincidence we have a similar issue for some CPU hotplug
> related bring up where review feedback was move all cases later).
>
> > + */
> > + continue;
> > +
> > memtier = set_node_memory_tier(node);
> > if (IS_ERR(memtier))
> > /*
>
--
Best regards,
Ho-Ren (Jack) Chuang
莊賀任
"Ho-Ren (Jack) Chuang" <[email protected]> writes:
> On Fri, Apr 5, 2024 at 7:03 AM Jonathan Cameron
> <[email protected]> wrote:
>>
>> On Fri, 5 Apr 2024 00:07:06 +0000
>> "Ho-Ren (Jack) Chuang" <[email protected]> wrote:
>>
>> > The current implementation treats emulated memory devices, such as
>> > CXL1.1 type3 memory, as normal DRAM when they are emulated as normal memory
>> > (E820_TYPE_RAM). However, these emulated devices have different
>> > characteristics than traditional DRAM, making it important to
>> > distinguish them. Thus, we modify the tiered memory initialization process
>> > to introduce a delay specifically for CPUless NUMA nodes. This delay
>> > ensures that the memory tier initialization for these nodes is deferred
>> > until HMAT information is obtained during the boot process. Finally,
>> > demotion tables are recalculated at the end.
>> >
>> > * late_initcall(memory_tier_late_init);
>> > Some device drivers may have initialized memory tiers between
>> > `memory_tier_init()` and `memory_tier_late_init()`, potentially bringing
>> > online memory nodes and configuring memory tiers. They should be excluded
>> > in the late init.
>> >
>> > * Handle cases where there is no HMAT when creating memory tiers
>> > There is a scenario where a CPUless node does not provide HMAT information.
>> > If no HMAT is specified, it falls back to using the default DRAM tier.
>> >
>> > * Introduce another new lock `default_dram_perf_lock` for adist calculation
>> > In the current implementation, iterating through CPUlist nodes requires
>> > holding the `memory_tier_lock`. However, `mt_calc_adistance()` will end up
>> > trying to acquire the same lock, leading to a potential deadlock.
>> > Therefore, we propose introducing a standalone `default_dram_perf_lock` to
>> > protect `default_dram_perf_*`. This approach not only avoids deadlock
>> > but also prevents holding a large lock simultaneously.
>> >
>> > * Upgrade `set_node_memory_tier` to support additional cases, including
>> > default DRAM, late CPUless, and hot-plugged initializations.
>> > To cover hot-plugged memory nodes, `mt_calc_adistance()` and
>> > `mt_find_alloc_memory_type()` are moved into `set_node_memory_tier()` to
>> > handle cases where memtype is not initialized and where HMAT information is
>> > available.
>> >
>> > * Introduce `default_memory_types` for those memory types that are not
>> > initialized by device drivers.
>> > Because late initialized memory and default DRAM memory need to be managed,
>> > a default memory type is created for storing all memory types that are
>> > not initialized by device drivers and as a fallback.
>> >
>> > Signed-off-by: Ho-Ren (Jack) Chuang <[email protected]>
>> > Signed-off-by: Hao Xiang <[email protected]>
>> > Reviewed-by: "Huang, Ying" <[email protected]>
>>
>> Hi - one remaining question. Why can't we delay init for all nodes
>> to either drivers or your fallback late_initcall code.
>> It would be nice to reduce possible code paths.
>
> I try not to change too much of the existing code structure in
> this patchset.
>
> To me, postponing/moving all memory tier registrations to
> late_initcall() is another possible action item for the next patchset.
>
> After tier_mem(), hmat_init() is called, which requires registering
> `default_dram_type` info. This is when `default_dram_type` is needed.
> However, it is indeed possible to postpone the latter part,
> set_node_memory_tier(), to `late_init(). So, memory_tier_init() can
> indeed be split into two parts, and the latter part can be moved to
> late_initcall() to be processed together.
I don't think that it's good to move all memory_tier initialization in
drivers to late_initcall(). It's natural to keep them in
device_initcall() level.
If so, we can allocate default_dram_type in memory_tier_init(), and call
set_node_memory_tier() only in memory_tier_lateinit(). We can call
memory_tier_lateinit() in device_initcall() level too.
--
Best Regards,
Huang, Ying
> Doing this all memory-type drivers have to call late_initcall() to
> register a memory tier. I’m not sure how many they are?
>
> What do you guys think?
>
>>
>> Jonathan
>>
>>
>> > ---
>> > mm/memory-tiers.c | 94 +++++++++++++++++++++++++++++++++++------------
>> > 1 file changed, 70 insertions(+), 24 deletions(-)
>> >
>> > diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
>> > index 516b144fd45a..6632102bd5c9 100644
>> > --- a/mm/memory-tiers.c
>> > +++ b/mm/memory-tiers.c
>>
>>
>>
>> > @@ -855,7 +892,8 @@ static int __init memory_tier_init(void)
>> > * For now we can have 4 faster memory tiers with smaller adistance
>> > * than default DRAM tier.
>> > */
>> > - default_dram_type = alloc_memory_type(MEMTIER_ADISTANCE_DRAM);
>> > + default_dram_type = mt_find_alloc_memory_type(MEMTIER_ADISTANCE_DRAM,
>> > + &default_memory_types);
>> > if (IS_ERR(default_dram_type))
>> > panic("%s() failed to allocate default DRAM tier\n", __func__);
>> >
>> > @@ -865,6 +903,14 @@ static int __init memory_tier_init(void)
>> > * types assigned.
>> > */
>> > for_each_node_state(node, N_MEMORY) {
>> > + if (!node_state(node, N_CPU))
>> > + /*
>> > + * Defer memory tier initialization on
>> > + * CPUless numa nodes. These will be initialized
>> > + * after firmware and devices are initialized.
>>
>> Could the comment also say why we can't defer them all?
>>
>> (In an odd coincidence we have a similar issue for some CPU hotplug
>> related bring up where review feedback was move all cases later).
>>
>> > + */
>> > + continue;
>> > +
>> > memtier = set_node_memory_tier(node);
>> > if (IS_ERR(memtier))
>> > /*
>>
On Tue, Apr 9, 2024 at 7:33 PM Huang, Ying <[email protected]> wrote:
>
> "Ho-Ren (Jack) Chuang" <[email protected]> writes:
>
> > On Fri, Apr 5, 2024 at 7:03 AM Jonathan Cameron
> > <[email protected]> wrote:
> >>
> >> On Fri, 5 Apr 2024 00:07:06 +0000
> >> "Ho-Ren (Jack) Chuang" <[email protected]> wrote:
> >>
> >> > The current implementation treats emulated memory devices, such as
> >> > CXL1.1 type3 memory, as normal DRAM when they are emulated as normal memory
> >> > (E820_TYPE_RAM). However, these emulated devices have different
> >> > characteristics than traditional DRAM, making it important to
> >> > distinguish them. Thus, we modify the tiered memory initialization process
> >> > to introduce a delay specifically for CPUless NUMA nodes. This delay
> >> > ensures that the memory tier initialization for these nodes is deferred
> >> > until HMAT information is obtained during the boot process. Finally,
> >> > demotion tables are recalculated at the end.
> >> >
> >> > * late_initcall(memory_tier_late_init);
> >> > Some device drivers may have initialized memory tiers between
> >> > `memory_tier_init()` and `memory_tier_late_init()`, potentially bringing
> >> > online memory nodes and configuring memory tiers. They should be excluded
> >> > in the late init.
> >> >
> >> > * Handle cases where there is no HMAT when creating memory tiers
> >> > There is a scenario where a CPUless node does not provide HMAT information.
> >> > If no HMAT is specified, it falls back to using the default DRAM tier.
> >> >
> >> > * Introduce another new lock `default_dram_perf_lock` for adist calculation
> >> > In the current implementation, iterating through CPUlist nodes requires
> >> > holding the `memory_tier_lock`. However, `mt_calc_adistance()` will end up
> >> > trying to acquire the same lock, leading to a potential deadlock.
> >> > Therefore, we propose introducing a standalone `default_dram_perf_lock` to
> >> > protect `default_dram_perf_*`. This approach not only avoids deadlock
> >> > but also prevents holding a large lock simultaneously.
> >> >
> >> > * Upgrade `set_node_memory_tier` to support additional cases, including
> >> > default DRAM, late CPUless, and hot-plugged initializations.
> >> > To cover hot-plugged memory nodes, `mt_calc_adistance()` and
> >> > `mt_find_alloc_memory_type()` are moved into `set_node_memory_tier()` to
> >> > handle cases where memtype is not initialized and where HMAT information is
> >> > available.
> >> >
> >> > * Introduce `default_memory_types` for those memory types that are not
> >> > initialized by device drivers.
> >> > Because late initialized memory and default DRAM memory need to be managed,
> >> > a default memory type is created for storing all memory types that are
> >> > not initialized by device drivers and as a fallback.
> >> >
> >> > Signed-off-by: Ho-Ren (Jack) Chuang <[email protected]>
> >> > Signed-off-by: Hao Xiang <[email protected]>
> >> > Reviewed-by: "Huang, Ying" <[email protected]>
> >>
> >> Hi - one remaining question. Why can't we delay init for all nodes
> >> to either drivers or your fallback late_initcall code.
> >> It would be nice to reduce possible code paths.
> >
> > I try not to change too much of the existing code structure in
> > this patchset.
> >
> > To me, postponing/moving all memory tier registrations to
> > late_initcall() is another possible action item for the next patchset.
> >
> > After tier_mem(), hmat_init() is called, which requires registering
> > `default_dram_type` info. This is when `default_dram_type` is needed.
> > However, it is indeed possible to postpone the latter part,
> > set_node_memory_tier(), to `late_init(). So, memory_tier_init() can
> > indeed be split into two parts, and the latter part can be moved to
> > late_initcall() to be processed together.
>
> I don't think that it's good to move all memory_tier initialization in
> drivers to late_initcall(). It's natural to keep them in
> device_initcall() level.
>
> If so, we can allocate default_dram_type in memory_tier_init(), and call
> set_node_memory_tier() only in memory_tier_lateinit(). We can call
> memory_tier_lateinit() in device_initcall() level too.
>
It makes sense to me to leave only `default_dram_type ` and
hotplug_init() in memory_tier_init(), postponing all
set_node_memory_tier()s to memory_tier_late_init()
Would it be possible there is no device_initcall() calling
memory_tier_late_init()? If yes, I think putting memory_tier_late_init()
in late_init() is still necessary.
> --
> Best Regards,
> Huang, Ying
>
> > Doing this all memory-type drivers have to call late_initcall() to
> > register a memory tier. I’m not sure how many they are?
> >
> > What do you guys think?
> >
> >>
> >> Jonathan
> >>
> >>
> >> > ---
> >> > mm/memory-tiers.c | 94 +++++++++++++++++++++++++++++++++++------------
> >> > 1 file changed, 70 insertions(+), 24 deletions(-)
> >> >
> >> > diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
> >> > index 516b144fd45a..6632102bd5c9 100644
> >> > --- a/mm/memory-tiers.c
> >> > +++ b/mm/memory-tiers.c
> >>
> >>
> >>
> >> > @@ -855,7 +892,8 @@ static int __init memory_tier_init(void)
> >> > * For now we can have 4 faster memory tiers with smaller adistance
> >> > * than default DRAM tier.
> >> > */
> >> > - default_dram_type = alloc_memory_type(MEMTIER_ADISTANCE_DRAM);
> >> > + default_dram_type = mt_find_alloc_memory_type(MEMTIER_ADISTANCE_DRAM,
> >> > + &default_memory_types);
> >> > if (IS_ERR(default_dram_type))
> >> > panic("%s() failed to allocate default DRAM tier\n", __func__);
> >> >
> >> > @@ -865,6 +903,14 @@ static int __init memory_tier_init(void)
> >> > * types assigned.
> >> > */
> >> > for_each_node_state(node, N_MEMORY) {
> >> > + if (!node_state(node, N_CPU))
> >> > + /*
> >> > + * Defer memory tier initialization on
> >> > + * CPUless numa nodes. These will be initialized
> >> > + * after firmware and devices are initialized.
> >>
> >> Could the comment also say why we can't defer them all?
> >>
> >> (In an odd coincidence we have a similar issue for some CPU hotplug
> >> related bring up where review feedback was move all cases later).
> >>
> >> > + */
> >> > + continue;
> >> > +
> >> > memtier = set_node_memory_tier(node);
> >> > if (IS_ERR(memtier))
> >> > /*
> >>
--
Best regards,
Ho-Ren (Jack) Chuang
莊賀任
On Fri, 5 Apr 2024 15:43:47 -0700
"Ho-Ren (Jack) Chuang" <[email protected]> wrote:
> On Fri, Apr 5, 2024 at 7:03 AM Jonathan Cameron
> <[email protected]> wrote:
> >
> > On Fri, 5 Apr 2024 00:07:06 +0000
> > "Ho-Ren (Jack) Chuang" <[email protected]> wrote:
> >
> > > The current implementation treats emulated memory devices, such as
> > > CXL1.1 type3 memory, as normal DRAM when they are emulated as normal memory
> > > (E820_TYPE_RAM). However, these emulated devices have different
> > > characteristics than traditional DRAM, making it important to
> > > distinguish them. Thus, we modify the tiered memory initialization process
> > > to introduce a delay specifically for CPUless NUMA nodes. This delay
> > > ensures that the memory tier initialization for these nodes is deferred
> > > until HMAT information is obtained during the boot process. Finally,
> > > demotion tables are recalculated at the end.
> > >
> > > * late_initcall(memory_tier_late_init);
> > > Some device drivers may have initialized memory tiers between
> > > `memory_tier_init()` and `memory_tier_late_init()`, potentially bringing
> > > online memory nodes and configuring memory tiers. They should be excluded
> > > in the late init.
> > >
> > > * Handle cases where there is no HMAT when creating memory tiers
> > > There is a scenario where a CPUless node does not provide HMAT information.
> > > If no HMAT is specified, it falls back to using the default DRAM tier.
> > >
> > > * Introduce another new lock `default_dram_perf_lock` for adist calculation
> > > In the current implementation, iterating through CPUlist nodes requires
> > > holding the `memory_tier_lock`. However, `mt_calc_adistance()` will end up
> > > trying to acquire the same lock, leading to a potential deadlock.
> > > Therefore, we propose introducing a standalone `default_dram_perf_lock` to
> > > protect `default_dram_perf_*`. This approach not only avoids deadlock
> > > but also prevents holding a large lock simultaneously.
> > >
> > > * Upgrade `set_node_memory_tier` to support additional cases, including
> > > default DRAM, late CPUless, and hot-plugged initializations.
> > > To cover hot-plugged memory nodes, `mt_calc_adistance()` and
> > > `mt_find_alloc_memory_type()` are moved into `set_node_memory_tier()` to
> > > handle cases where memtype is not initialized and where HMAT information is
> > > available.
> > >
> > > * Introduce `default_memory_types` for those memory types that are not
> > > initialized by device drivers.
> > > Because late initialized memory and default DRAM memory need to be managed,
> > > a default memory type is created for storing all memory types that are
> > > not initialized by device drivers and as a fallback.
> > >
> > > Signed-off-by: Ho-Ren (Jack) Chuang <[email protected]>
> > > Signed-off-by: Hao Xiang <[email protected]>
> > > Reviewed-by: "Huang, Ying" <[email protected]>
> >
> > Hi - one remaining question. Why can't we delay init for all nodes
> > to either drivers or your fallback late_initcall code.
> > It would be nice to reduce possible code paths.
>
> I try not to change too much of the existing code structure in
> this patchset.
>
> To me, postponing/moving all memory tier registrations to
> late_initcall() is another possible action item for the next patchset.
>
> After tier_mem(), hmat_init() is called, which requires registering
> `default_dram_type` info. This is when `default_dram_type` is needed.
> However, it is indeed possible to postpone the latter part,
> set_node_memory_tier(), to `late_init(). So, memory_tier_init() can
> indeed be split into two parts, and the latter part can be moved to
> late_initcall() to be processed together.
>
> Doing this all memory-type drivers have to call late_initcall() to
> register a memory tier. I’m not sure how many they are?
>
> What do you guys think?
Gut feeling - if you are going to move it for some cases, move it for
all of them. Then we only have to test once ;)
J
>
> >
> > Jonathan
> >
> >
> > > ---
> > > mm/memory-tiers.c | 94 +++++++++++++++++++++++++++++++++++------------
> > > 1 file changed, 70 insertions(+), 24 deletions(-)
> > >
> > > diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
> > > index 516b144fd45a..6632102bd5c9 100644
> > > --- a/mm/memory-tiers.c
> > > +++ b/mm/memory-tiers.c
> >
> >
> >
> > > @@ -855,7 +892,8 @@ static int __init memory_tier_init(void)
> > > * For now we can have 4 faster memory tiers with smaller adistance
> > > * than default DRAM tier.
> > > */
> > > - default_dram_type = alloc_memory_type(MEMTIER_ADISTANCE_DRAM);
> > > + default_dram_type = mt_find_alloc_memory_type(MEMTIER_ADISTANCE_DRAM,
> > > + &default_memory_types);
> > > if (IS_ERR(default_dram_type))
> > > panic("%s() failed to allocate default DRAM tier\n", __func__);
> > >
> > > @@ -865,6 +903,14 @@ static int __init memory_tier_init(void)
> > > * types assigned.
> > > */
> > > for_each_node_state(node, N_MEMORY) {
> > > + if (!node_state(node, N_CPU))
> > > + /*
> > > + * Defer memory tier initialization on
> > > + * CPUless numa nodes. These will be initialized
> > > + * after firmware and devices are initialized.
> >
> > Could the comment also say why we can't defer them all?
> >
> > (In an odd coincidence we have a similar issue for some CPU hotplug
> > related bring up where review feedback was move all cases later).
> >
> > > + */
> > > + continue;
> > > +
> > > memtier = set_node_memory_tier(node);
> > > if (IS_ERR(memtier))
> > > /*
> >
>
>
On Fri, 5 Apr 2024 00:07:06 +0000
"Ho-Ren (Jack) Chuang" <[email protected]> wrote:
> The current implementation treats emulated memory devices, such as
> CXL1.1 type3 memory, as normal DRAM when they are emulated as normal memory
> (E820_TYPE_RAM). However, these emulated devices have different
> characteristics than traditional DRAM, making it important to
> distinguish them. Thus, we modify the tiered memory initialization process
> to introduce a delay specifically for CPUless NUMA nodes. This delay
> ensures that the memory tier initialization for these nodes is deferred
> until HMAT information is obtained during the boot process. Finally,
> demotion tables are recalculated at the end.
>
> * late_initcall(memory_tier_late_init);
> Some device drivers may have initialized memory tiers between
> `memory_tier_init()` and `memory_tier_late_init()`, potentially bringing
> online memory nodes and configuring memory tiers. They should be excluded
> in the late init.
>
> * Handle cases where there is no HMAT when creating memory tiers
> There is a scenario where a CPUless node does not provide HMAT information.
> If no HMAT is specified, it falls back to using the default DRAM tier.
>
> * Introduce another new lock `default_dram_perf_lock` for adist calculation
> In the current implementation, iterating through CPUlist nodes requires
> holding the `memory_tier_lock`. However, `mt_calc_adistance()` will end up
> trying to acquire the same lock, leading to a potential deadlock.
> Therefore, we propose introducing a standalone `default_dram_perf_lock` to
> protect `default_dram_perf_*`. This approach not only avoids deadlock
> but also prevents holding a large lock simultaneously.
>
> * Upgrade `set_node_memory_tier` to support additional cases, including
> default DRAM, late CPUless, and hot-plugged initializations.
> To cover hot-plugged memory nodes, `mt_calc_adistance()` and
> `mt_find_alloc_memory_type()` are moved into `set_node_memory_tier()` to
> handle cases where memtype is not initialized and where HMAT information is
> available.
>
> * Introduce `default_memory_types` for those memory types that are not
> initialized by device drivers.
> Because late initialized memory and default DRAM memory need to be managed,
> a default memory type is created for storing all memory types that are
> not initialized by device drivers and as a fallback.
>
> Signed-off-by: Ho-Ren (Jack) Chuang <[email protected]>
> Signed-off-by: Hao Xiang <[email protected]>
> Reviewed-by: "Huang, Ying" <[email protected]>
Hi - one remaining question. Why can't we delay init for all nodes
to either drivers or your fallback late_initcall code.
It would be nice to reduce possible code paths.
Jonathan
> ---
> mm/memory-tiers.c | 94 +++++++++++++++++++++++++++++++++++------------
> 1 file changed, 70 insertions(+), 24 deletions(-)
>
> diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
> index 516b144fd45a..6632102bd5c9 100644
> --- a/mm/memory-tiers.c
> +++ b/mm/memory-tiers.c
> @@ -855,7 +892,8 @@ static int __init memory_tier_init(void)
> * For now we can have 4 faster memory tiers with smaller adistance
> * than default DRAM tier.
> */
> - default_dram_type = alloc_memory_type(MEMTIER_ADISTANCE_DRAM);
> + default_dram_type = mt_find_alloc_memory_type(MEMTIER_ADISTANCE_DRAM,
> + &default_memory_types);
> if (IS_ERR(default_dram_type))
> panic("%s() failed to allocate default DRAM tier\n", __func__);
>
> @@ -865,6 +903,14 @@ static int __init memory_tier_init(void)
> * types assigned.
> */
> for_each_node_state(node, N_MEMORY) {
> + if (!node_state(node, N_CPU))
> + /*
> + * Defer memory tier initialization on
> + * CPUless numa nodes. These will be initialized
> + * after firmware and devices are initialized.
Could the comment also say why we can't defer them all?
(In an odd coincidence we have a similar issue for some CPU hotplug
related bring up where review feedback was move all cases later).
> + */
> + continue;
> +
> memtier = set_node_memory_tier(node);
> if (IS_ERR(memtier))
> /*
On Fri, 5 Apr 2024 00:07:05 +0000
"Ho-Ren (Jack) Chuang" <[email protected]> wrote:
> Since different memory devices require finding, allocating, and putting
> memory types, these common steps are abstracted in this patch,
> enhancing the scalability and conciseness of the code.
>
> Signed-off-by: Ho-Ren (Jack) Chuang <[email protected]>
> Reviewed-by: "Huang, Ying" <[email protected]>
Reviewed-by: Jonathan Cameron <[email protected]>