linux-kernel - Re: [PATCH 1/2] vmscan: promote shared file mapped pages

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Date:	Mon, 31 Oct 2011 13:12:24 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
Cc:	<linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH 1/2] vmscan: promote shared file mapped pages

On Mon, 8 Aug 2011 15:06:58 +0400
Konstantin Khlebnikov <khlebnikov@...nvz.org> wrote:

> Commit v2.6.33-5448-g6457474 (vmscan: detect mapped file pages used only once)
> greatly decreases lifetime of single-used mapped file pages.
> Unfortunately it also decreases life time of all shared mapped file pages.
> Because after commit v2.6.28-6130-gbf3f3bc (mm: don't mark_page_accessed in fault path)
> page-fault handler does not mark page active or even referenced.
> 
> Thus page_check_references() activates file page only if it was used twice while
> it stays in inactive list, meanwhile it activates anon pages after first access.
> Inactive list can be small enough, this way reclaimer can accidentally
> throw away any widely used page if it wasn't used twice in short period.
> 
> After this patch page_check_references() also activate file mapped page at first
> inactive list scan if this page is already used multiple times via several ptes.

We have quite a few acks on these two patches, but everyone wants to
see detailed performance testing.  That hasn't happened, and caution
dictates that I hold these patches out of linux-3.2, pending that
testing.

Of course, you're not the only person who can undertake that testing (hint).

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