From 997071bcb34005f42e0fe5bc7930e895b070f251 Mon Sep 17 00:00:00 2001 From: "K. Y. Srinivasan" Date: Thu, 15 Nov 2012 14:34:42 -0800 Subject: 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. [akpm@linux-foundation.org: coding-style tweak] Signed-off-by: K. Y. Srinivasan Acked-by: David Rientjes Acked-by: Dan Magenheimer Cc: Konrad Rzeszutek Wilk Cc: Jeremy Fitzhardinge Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/mmap.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'mm/mmap.c') diff --git a/mm/mmap.c b/mm/mmap.c index 2d942353d68..b064822be82 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -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 -- cgit v1.2.3