From: Glauber Costa <glommer@parallels.com>
To: Sha Zhengju <handai.szj@gmail.com>
Cc: cgroups@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.cz,
kamezawa.hiroyu@jp.fujitsu.com, akpm@linux-foundation.org,
mgorman@suse.de, Sha Zhengju <handai.szj@taobao.com>
Subject: Re: [PATCH 2/6] memcg: Don't account root memcg CACHE/RSS stats
Date: Wed, 20 Mar 2013 11:07:45 +0400 [thread overview]
Message-ID: <51496041.4090900@parallels.com> (raw)
In-Reply-To: <1363082977-3753-1-git-send-email-handai.szj@taobao.com>
On 03/12/2013 02:09 PM, Sha Zhengju wrote:
> If memcg is enabled and no non-root memcg exists, all allocated pages
> belong to root_mem_cgroup and go through root memcg statistics routines
> which brings some overheads.
>
> So for the sake of performance, we can give up accounting stats of root
> memcg for MEM_CGROUP_STAT_CACHE/RSS and instead we pay special attention
> to memcg_stat_show() while showing root memcg numbers:
> as we don't account root memcg stats anymore, the root_mem_cgroup->stat
> numbers are actually 0. So we fake these numbers by using stats of global
> state and all other memcg. That is for root memcg:
>
> nr(MEM_CGROUP_STAT_CACHE) = global_page_state(NR_FILE_PAGES) -
> sum_of_all_memcg(MEM_CGROUP_STAT_CACHE);
>
> Rss pages accounting are in the similar way.
>
Well,
The problem is that statistics is not the only cause for overhead. We
will still incur in in the whole charging operation, and the same for
uncharge. There is memory overhead from page_cgroup, etc.
So my view is that this patch is far from complete.
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next prev parent reply other threads:[~2013-03-20 7:07 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-12 10:06 [PATCH 0/6] memcg: bypass root memcg page stat accounting Sha Zhengju
2013-03-12 10:08 ` [PATCH 1/6] memcg: use global stat directly for root memcg usage Sha Zhengju
2013-03-13 1:05 ` Kamezawa Hiroyuki
2013-03-13 8:50 ` Sha Zhengju
2013-03-12 10:09 ` [PATCH 2/6] memcg: Don't account root memcg CACHE/RSS stats Sha Zhengju
2013-03-13 1:12 ` Kamezawa Hiroyuki
2013-03-13 9:09 ` Sha Zhengju
2013-03-20 7:07 ` Glauber Costa [this message]
2013-03-12 10:10 ` [PATCH 3/6] memcg: Don't account root memcg MEM_CGROUP_STAT_FILE_MAPPED stats Sha Zhengju
2013-03-12 10:10 ` [PATCH 4/6] memcg: Don't account root memcg swap stats Sha Zhengju
2013-03-12 10:11 ` [PATCH 5/6] memcg: Don't account root memcg PGFAULT/PGMAJFAULT events Sha Zhengju
2013-03-12 10:11 ` [PATCH 6/6] memcg: disable memcg page stat accounting Sha Zhengju
2013-03-20 7:09 ` Glauber Costa
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