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From: Johannes Weiner <hannes@cmpxchg.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
	Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>,
	Balbir Singh <balbir@linux.vnet.ibm.com>, <linux-mm@kvack.org>,
	<linux-kernel@vger.kernel.org>
Subject: memcg: save 20% of per-page memcg memory overhead
Date: Thu,  3 Feb 2011 15:26:01 +0100	[thread overview]
Message-ID: <1296743166-9412-1-git-send-email-hannes@cmpxchg.org> (raw)

This patch series removes the direct page pointer from struct
page_cgroup, which saves 20% of per-page memcg memory overhead (Fedora
and Ubuntu enable memcg per default, openSUSE apparently too).

The node id or section number is encoded in the remaining free bits of
pc->flags which allows calculating the corresponding page without the
extra pointer.

I ran, what I think is, a worst-case microbenchmark that just cats a
large sparse file to /dev/null, because it means that walking the LRU
list on behalf of per-cgroup reclaim and looking up pages from
page_cgroups is happening constantly and at a high rate.  But it made
no measurable difference.  A profile reported a 0.11% share of the new
lookup_cgroup_page() function in this benchmark.

	Hannes

             reply	other threads:[~2011-02-03 14:28 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-02-03 14:26 Johannes Weiner [this message]
2011-02-03 14:26 ` [patch 1/5] memcg: no uncharged pages reach page_cgroup_zoneinfo Johannes Weiner
2011-02-04  0:01   ` KAMEZAWA Hiroyuki
2011-02-04  9:26     ` Johannes Weiner
2011-02-04  9:23       ` KAMEZAWA Hiroyuki
2011-02-04  4:16   ` Balbir Singh
2011-02-03 14:26 ` [patch 2/5] memcg: change page_cgroup_zoneinfo signature Johannes Weiner
2011-02-04  0:03   ` KAMEZAWA Hiroyuki
2011-02-03 14:26 ` [patch 3/5] memcg: fold __mem_cgroup_move_account into caller Johannes Weiner
2011-02-04  0:07   ` KAMEZAWA Hiroyuki
2011-02-04  0:53     ` Daisuke Nishimura
2011-02-03 14:26 ` [patch 4/5] memcg: condense page_cgroup-to-page lookup points Johannes Weiner
2011-02-04  0:10   ` KAMEZAWA Hiroyuki
2011-02-03 14:26 ` [patch 5/5] memcg: remove direct page_cgroup-to-page pointer Johannes Weiner
2011-02-04  0:19   ` KAMEZAWA Hiroyuki
2011-02-04  9:51     ` Johannes Weiner
2011-02-03 15:02 ` memcg: save 20% of per-page memcg memory overhead Balbir Singh

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