Merge tag 'stable/for-linus-3.14-rc0-late-tag' of git://git.kernel.org/pub/scm/linux...

[firefly-linux-kernel-4.4.55.git] / drivers / xen / xen-selfballoon.c

diff --git a/drivers/xen/xen-selfballoon.c b/drivers/xen/xen-selfballoon.c
index 21e18c18c7a17e6c1befc5f4447a0a814a8ab398..745ad79c1d8e3e85255717b470eb13aac44c4fcb 100644 (file)
--- 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;