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authorK. Y. Srinivasan <kys@microsoft.com>2012-11-15 14:34:42 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-11-15 15:41:22 -0800
commit997071bcb34005f42e0fe5bc7930e895b070f251 (patch)
tree7cc8056370e1c77314fdf0b3fd72bcc69743f24c /mm/mmap.c
parentd892de8d3fb1e807de561289cfb1fed42950440a (diff)
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 <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>
Diffstat (limited to 'mm/mmap.c')
-rw-r--r--mm/mmap.c14
1 files changed, 14 insertions, 0 deletions
diff --git a/mm/mmap.c b/mm/mmap.c
index 2d942353d68..b064822be82 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -89,6 +89,20 @@ 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
* succeed and -ENOMEM implies there is not.