linux-kernel - memcg: save 20% of per-page memcg memory overhead

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Thu,  3 Feb 2011 15:26:01 +0100
From:	Johannes Weiner <hannes@...xchg.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>
Subject: memcg: save 20% of per-page memcg memory overhead

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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/