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authorBob Liu <lliubbo@gmail.com>2014-01-22 14:57:44 +0800
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2014-01-31 09:48:43 -0500
commitbc1b0df59e3fc4573f92bc1aab9652047a0aeaa7 (patch)
tree53cc9ed64066763826df51f914556c9f88a2a864
parent08ece5bb2312b4510b161a6ef6682f37f4eac8a1 (diff)
downloadlinux-linaro-stable-bc1b0df59e3fc4573f92bc1aab9652047a0aeaa7.tar.gz
drivers: xen: deaggressive selfballoon driver
Current xen-selfballoon driver is too aggressive which may cause OOM be triggered more often. Eg. this bug reported by James: https://lkml.org/lkml/2013/11/21/158 There are two mainly reasons: 1) The original goal_page didn't consider some pages used by kernel space, like slab pages and pages used by device drivers. 2) The balloon driver may not give back memory to guest OS fast enough when the workload suddenly aquries a lot of physical memory. In both cases, the guest OS will suffer from memory pressure and OOM may be triggered. The fix is make xen-selfballoon driver not that aggressive by adding extra 10% of total ram pages to goal_page. It's more valuable to keep the guest system reliable and response faster than balloon out these 10% pages to XEN. Signed-off-by: Bob Liu <bob.liu@oracle.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
-rw-r--r--drivers/xen/xen-selfballoon.c22
1 files changed, 22 insertions, 0 deletions
diff --git a/drivers/xen/xen-selfballoon.c b/drivers/xen/xen-selfballoon.c
index 21e18c18c7a1..745ad79c1d8e 100644
--- a/drivers/xen/xen-selfballoon.c
+++ b/drivers/xen/xen-selfballoon.c
@@ -175,6 +175,7 @@ static void frontswap_selfshrink(void)
#endif /* CONFIG_FRONTSWAP */
#define MB2PAGES(mb) ((mb) << (20 - PAGE_SHIFT))
+#define PAGES2MB(pages) ((pages) >> (20 - PAGE_SHIFT))
/*
* Use current balloon size, the goal (vm_committed_as), and hysteresis
@@ -525,6 +526,7 @@ EXPORT_SYMBOL(register_xen_selfballooning);
int xen_selfballoon_init(bool use_selfballooning, bool use_frontswap_selfshrink)
{
bool enable = false;
+ unsigned long reserve_pages;
if (!xen_domain())
return -ENODEV;
@@ -549,6 +551,26 @@ int xen_selfballoon_init(bool use_selfballooning, bool use_frontswap_selfshrink)
if (!enable)
return -ENODEV;
+ /*
+ * Give selfballoon_reserved_mb a default value(10% of total ram pages)
+ * to make selfballoon not so aggressive.
+ *
+ * There are mainly two reasons:
+ * 1) The original goal_page didn't consider some pages used by kernel
+ * space, like slab pages and memory used by device drivers.
+ *
+ * 2) The balloon driver may not give back memory to guest OS fast
+ * enough when the workload suddenly aquries a lot of physical memory.
+ *
+ * In both cases, the guest OS will suffer from memory pressure and
+ * OOM killer may be triggered.
+ * By reserving extra 10% of total ram pages, we can keep the system
+ * much more reliably and response faster in some cases.
+ */
+ if (!selfballoon_reserved_mb) {
+ reserve_pages = totalram_pages / 10;
+ selfballoon_reserved_mb = PAGES2MB(reserve_pages);
+ }
schedule_delayed_work(&selfballoon_worker, selfballoon_interval * HZ);
return 0;