From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
To: Andrew Bresticker <abrestic@google.com>
Cc: Paul Menage <menage@google.com>, Li Zefan <lizf@cn.fujitsu.com>,
Ying Han <yinghan@google.com>,
linux-mm@kvack.org
Subject: Re: [PATCH] memcg: replace ss->id_lock with a rwlock
Date: Thu, 11 Aug 2011 09:02:11 +0900 [thread overview]
Message-ID: <20110811090211.77d380fb.kamezawa.hiroyu@jp.fujitsu.com> (raw)
In-Reply-To: <1313000433-11537-1-git-send-email-abrestic@google.com>
On Wed, 10 Aug 2011 11:20:33 -0700
Andrew Bresticker <abrestic@google.com> wrote:
> While back-porting Johannes Weiner's patch "mm: memcg-aware global reclaim"
> for an internal effort, we noticed a significant performance regression
> during page-reclaim heavy workloads due to high contention of the ss->id_lock.
> This lock protects idr map, and serializes calls to idr_get_next() in
> css_get_next() (which is used during the memcg hierarchy walk). Since
> idr_get_next() is just doing a look up, we need only serialize it with
> respect to idr_remove()/idr_get_new(). By making the ss->id_lock a
> rwlock, contention is greatly reduced and performance improves.
>
> Tested: cat a 256m file from a ramdisk in a 128m container 50 times
> on each core (one file + container per core) in parallel on a NUMA
> machine. Result is the time for the test to complete in 1 of the
> containers. Both kernels included Johannes' memcg-aware global
> reclaim patches.
> Before rwlock patch: 1710.778s
> After rwlock patch: 152.227s
>
> Signed-off-by: Andrew Bresticker <abrestic@google.com>
Hopefully, the changelog should be based on the latest Linus's git tree
or mmotm. Even now, if a system has multiple hierarchies of memcg, I think
the contention will happen.
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
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next prev parent reply other threads:[~2011-08-11 0:09 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-10 18:20 Andrew Bresticker
2011-08-11 0:02 ` KAMEZAWA Hiroyuki [this message]
2011-08-19 13:55 ` Johannes Weiner
2011-08-24 4:10 ` Ying Han
2011-08-24 4:12 ` Ying Han
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