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mm: export a function to get vm committed memory

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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.

[akpm@linux-foundation.org: coding-style tweak]
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
K. Y. Srinivasan 2012-11-15 14:34:42 -08:00 committed by Greg Kroah-Hartman
parent d892de8d3f
commit 997071bcb3
4 changed files with 32 additions and 1 deletions
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2
drivers/xen/xen-selfballoon.c
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@ -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

2
include/linux/mman.h
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@ -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);

14
mm/mmap.c
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@ -88,6 +88,20 @@ 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

15
mm/nommu.c
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@ -66,6 +66,21 @@ 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);