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-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;