It will be useful to be able to access global memory commitment from device
drivers. On the Hyper-V platform, the host has a policy engine to balance
the available physical memory amongst all competing virtual machines
hosted on a given node. This policy engine is driven by a number of metrics
including the memory commitment reported by the guests. The balloon driver
for Linux on Hyper-V will use this function to retrieve guest memory commitment.
This function is also used in Xen self ballooning code.
Signed-off-by: K. Y. Srinivasan <[email protected]>
---
drivers/xen/xen-selfballoon.c | 2 +-
include/linux/mman.h | 2 ++
mm/mmap.c | 15 +++++++++++++++
mm/nommu.c | 16 ++++++++++++++++
4 files changed, 34 insertions(+), 1 deletions(-)
diff --git a/drivers/xen/xen-selfballoon.c b/drivers/xen/xen-selfballoon.c
index 7d041cb..2552d3e 100644
--- a/drivers/xen/xen-selfballoon.c
+++ b/drivers/xen/xen-selfballoon.c
@@ -222,7 +222,7 @@ static void selfballoon_process(struct work_struct *work)
if (xen_selfballooning_enabled) {
cur_pages = totalram_pages;
tgt_pages = cur_pages; /* default is no change */
- goal_pages = percpu_counter_read_positive(&vm_committed_as) +
+ goal_pages = vm_memory_committed() +
totalreserve_pages +
MB2PAGES(selfballoon_reserved_mb);
#ifdef CONFIG_FRONTSWAP
diff --git a/include/linux/mman.h b/include/linux/mman.h
index d09dde1..9aa863d 100644
--- a/include/linux/mman.h
+++ b/include/linux/mman.h
@@ -11,6 +11,8 @@ extern int sysctl_overcommit_memory;
extern int sysctl_overcommit_ratio;
extern struct percpu_counter vm_committed_as;
+unsigned long vm_memory_committed(void);
+
static inline void vm_acct_memory(long pages)
{
percpu_counter_add(&vm_committed_as, pages);
diff --git a/mm/mmap.c b/mm/mmap.c
index 2d94235..3dd0a17 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -89,6 +89,21 @@ int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;
/*
+ * The global memory commitment made in the system can be a metric
+ * that can be used to drive ballooning decisions when Linux is hosted
+ * as a guest. On Hyper-V, the host implements a policy engine for dynamically
+ * balancing memory across competing virtual machines that are hosted.
+ * Several metrics drive this policy engine including the guest reported
+ * memory commitment.
+ */
+
+unsigned long vm_memory_committed(void)
+{
+ return percpu_counter_read_positive(&vm_committed_as);
+}
+EXPORT_SYMBOL_GPL(vm_memory_committed);
+
+/*
* Check that a process has enough memory to allocate a new virtual
* mapping. 0 means there is enough memory for the allocation to
* succeed and -ENOMEM implies there is not.
diff --git a/mm/nommu.c b/mm/nommu.c
index 45131b4..f11e703 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -66,6 +66,22 @@ int heap_stack_gap = 0;
atomic_long_t mmap_pages_allocated;
+/*
+ * The global memory commitment made in the system can be a metric
+ * that can be used to drive ballooning decisions when Linux is hosted
+ * as a guest. On Hyper-V, the host implements a policy engine for dynamically
+ * balancing memory across competing virtual machines that are hosted.
+ * Several metrics drive this policy engine including the guest reported
+ * memory commitment.
+ */
+
+unsigned long vm_memory_committed(void)
+{
+ return percpu_counter_read_positive(&vm_committed_as);
+}
+
+EXPORT_SYMBOL_GPL(vm_memory_committed);
+
EXPORT_SYMBOL(mem_map);
EXPORT_SYMBOL(num_physpages);
--
1.7.4.1
> From: K. Y. Srinivasan [mailto:[email protected]]
> Sent: Tuesday, November 13, 2012 8:03 AM
> To: [email protected]; [email protected]; [email protected];
> [email protected]; [email protected]; [email protected]; [email protected]; [email protected];
> [email protected]; [email protected]; [email protected]; [email protected];
> [email protected]; [email protected]
> Cc: K. Y. Srinivasan
> Subject: [PATCH 1/1] mm: Export a function to get vm committed memory
>
> It will be useful to be able to access global memory commitment from device
> drivers. On the Hyper-V platform, the host has a policy engine to balance
> the available physical memory amongst all competing virtual machines
> hosted on a given node. This policy engine is driven by a number of metrics
> including the memory commitment reported by the guests. The balloon driver
> for Linux on Hyper-V will use this function to retrieve guest memory commitment.
> This function is also used in Xen self ballooning code.
>
> Signed-off-by: K. Y. Srinivasan <[email protected]>
The patch to the Xen selfballoon driver is unnecessary, but is
one step in the direction of module support for this driver so
I am fine whether the patch is included here or not.
Acked-by: Dan Magenheimer <[email protected]>
On Tue, 13 Nov 2012, K. Y. Srinivasan wrote:
> It will be useful to be able to access global memory commitment from device
> drivers. On the Hyper-V platform, the host has a policy engine to balance
> the available physical memory amongst all competing virtual machines
> hosted on a given node. This policy engine is driven by a number of metrics
> including the memory commitment reported by the guests. The balloon driver
> for Linux on Hyper-V will use this function to retrieve guest memory commitment.
> This function is also used in Xen self ballooning code.
>
> Signed-off-by: K. Y. Srinivasan <[email protected]>
Acked-by: David Rientjes <[email protected]>
Very nice!
On Tue, Nov 13, 2012 at 01:07:30PM -0800, David Rientjes wrote:
> On Tue, 13 Nov 2012, K. Y. Srinivasan wrote:
>
> > It will be useful to be able to access global memory commitment from device
> > drivers. On the Hyper-V platform, the host has a policy engine to balance
> > the available physical memory amongst all competing virtual machines
> > hosted on a given node. This policy engine is driven by a number of metrics
> > including the memory commitment reported by the guests. The balloon driver
> > for Linux on Hyper-V will use this function to retrieve guest memory commitment.
> > This function is also used in Xen self ballooning code.
> >
> > Signed-off-by: K. Y. Srinivasan <[email protected]>
>
> Acked-by: David Rientjes <[email protected]>
I am bit late to this party - and back from vacation - so not sure if this
is merged in or not. Either way:
Acked-by: Konrad Rzeszutek Wilk <[email protected]> on the drivers/xen* side.