[RFC][PATCH 9/9] more event filter depend on priority

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

I'll revisit this one before v3...

==
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reduce softlimit update ratio depends on its priority(usage).

After this.
  if priority=0,1 -> check once in 1024 page-in/out
  if priority=2,3 -> check once in 2048 page-in/out
  ...
  if priority=10,11 -> check once in 32k page-in/out

(Note: this is called only when the usage exceeds soft limit)

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 mm/memcontrol.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

Index: softlimit-test2/mm/memcontrol.c
===================================================================
--- softlimit-test2.orig/mm/memcontrol.c
+++ softlimit-test2/mm/memcontrol.c
@@ -940,7 +940,7 @@ static void record_last_oom(struct mem_c
 	mem_cgroup_walk_tree(mem, NULL, record_last_oom_cb);
 }
 
-#define SOFTLIMIT_EVENTS_THRESH (1024) /* 1024 times of page-in/out */
+#define SOFTLIMIT_EVENTS_THRESH (512) /* 512 times of page-in/out */
 /*
  * Returns true if sum of page-in/page-out events since last check is
  * over SOFTLIMIT_EVENT_THRESH. (counter is per-cpu.)
@@ -950,11 +950,15 @@ static bool mem_cgroup_soft_limit_check(
 	bool ret = false;
 	int cpu = get_cpu();
 	s64 val;
+	int thresh;
 	struct mem_cgroup_stat_cpu *cpustat;
 
 	cpustat = &mem->stat.cpustat[cpu];
 	val = __mem_cgroup_stat_read_local(cpustat, MEM_CGROUP_STAT_EVENTS);
-	if (unlikely(val > SOFTLIMIT_EVENTS_THRESH)) {
+	/* If usage is big, this check can be rough */
+	thresh = SOFTLIMIT_EVENTS_THRESH;
+	thresh <<= ((mem->soft_limit_priority >> 1) + 1);
+	if (unlikely(val > thresh)) {
 		__mem_cgroup_stat_reset_safe(cpustat, MEM_CGROUP_STAT_EVENTS);
 		ret = true;
 	}

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