Commit 378ce724 authored by Kirill A. Shutemov's avatar Kirill A. Shutemov Committed by Linus Torvalds
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memcg: rework usage of stats by soft limit 



Instead of incrementing counter on each page in/out and comparing it with
constant, we set counter to constant, decrement counter on each page
in/out and compare it with zero.  We want to make comparing as fast as
possible.  On many RISC systems (probably not only RISC) comparing with
zero is more effective than comparing with a constant, since not every
constant can be immediate operand for compare instruction.

Also, I've renamed MEM_CGROUP_STAT_EVENTS to MEM_CGROUP_STAT_SOFTLIMIT,
since really it's not a generic counter.

Signed-off-by: default avatarKirill A. Shutemov <kirill@shutemov.name>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Dan Malek <dan@embeddedalley.com>
Cc: Vladislav Buzov <vbuzov@embeddedalley.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Alexander Shishkin <virtuoso@slind.org>
Cc: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 104f3928

mm/memcontrol.c

+10 −8
Original line number Diff line number Diff line
@@ -71,8 +71,9 @@ enum mem_cgroup_stat_index { 
	MEM_CGROUP_STAT_FILE_MAPPED,  /* # of pages charged as file rss */

	MEM_CGROUP_STAT_PGPGIN_COUNT,	/* # of pages paged in */

	MEM_CGROUP_STAT_PGPGOUT_COUNT,	/* # of pages paged out */

	MEM_CGROUP_STAT_EVENTS,	/* sum of pagein + pageout for internal use */

	MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */

	MEM_CGROUP_STAT_SOFTLIMIT, /* decrements on each page in/out.

					used by soft limit implementation */



	MEM_CGROUP_STAT_NSTATS,

};
@@ -86,10 +87,10 @@ struct mem_cgroup_stat { 
};



static inline void

__mem_cgroup_stat_reset_safe(struct mem_cgroup_stat_cpu *stat,

				enum mem_cgroup_stat_index idx)

__mem_cgroup_stat_set_safe(struct mem_cgroup_stat_cpu *stat,

				enum mem_cgroup_stat_index idx, s64 val)

{

	stat->count[idx] = 0;

	stat->count[idx] = val;

}



static inline s64
@@ -411,9 +412,10 @@ static bool mem_cgroup_soft_limit_check(struct mem_cgroup *mem) 


	cpu = get_cpu();

	cpustat = &mem->stat.cpustat[cpu];

	val = __mem_cgroup_stat_read_local(cpustat, MEM_CGROUP_STAT_EVENTS);

	if (unlikely(val > SOFTLIMIT_EVENTS_THRESH)) {

		__mem_cgroup_stat_reset_safe(cpustat, MEM_CGROUP_STAT_EVENTS);

	val = __mem_cgroup_stat_read_local(cpustat, MEM_CGROUP_STAT_SOFTLIMIT);

	if (unlikely(val < 0)) {

		__mem_cgroup_stat_set_safe(cpustat, MEM_CGROUP_STAT_SOFTLIMIT,

				SOFTLIMIT_EVENTS_THRESH);

		ret = true;

	}

	put_cpu();
@@ -546,7 +548,7 @@ static void mem_cgroup_charge_statistics(struct mem_cgroup *mem, 
	else

		__mem_cgroup_stat_add_safe(cpustat,

				MEM_CGROUP_STAT_PGPGOUT_COUNT, 1);

	__mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_EVENTS, 1);

	__mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_SOFTLIMIT, -1);

	put_cpu();

}

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