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>
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 @@
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_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..b064822 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -89,6 +89,20 @@
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..79c3cac 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -66,6 +66,21 @@
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);
