linux-kernel - Re: [RFC] respect the referenced bit of KVM guest pages?

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

Date:	Thu, 06 Aug 2009 09:16:14 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Wu Fengguang <fengguang.wu@...el.com>
CC:	Avi Kivity <avi@...hat.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	"Dike, Jeffrey G" <jeffrey.g.dike@...el.com>,
	"Yu, Wilfred" <wilfred.yu@...el.com>,
	"Kleen, Andi" <andi.kleen@...el.com>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Mel Gorman <mel@....ul.ie>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: [RFC] respect the referenced bit of KVM guest pages?

Wu Fengguang wrote:

> I guess both schemes have unacceptable flaws.
> 
> For JVM/BIGMEM workload, most pages would be found referenced _all the time_.
> So the KEEP_MOST scheme could increase reclaim overheads by N=250 times;
> while the DROP_CONTINUOUS scheme is effectively zero cost.

The higher overhead may not be an issue on smaller systems,
or inside smaller cgroups inside large systems, when doing
cgroup reclaim.

> However, the DROP_CONTINUOUS scheme does bring more _indeterminacy_.
> It can behave vastly different on single active task and multi ones.
> It is short sighted and can be cheated by bursty activities.

The split LRU VM tries to avoid the bursty page aging as
much as possible, by doing background deactivating of
anonymous pages whenever we reclaim page cache pages and
the number of anonymous pages in the zone (or cgroup) is
low.

-- 
All rights reversed.
--
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/