linux-kernel - Re: mm: used-once mapped file page detection

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Message-ID: <4B8AAC9A.10203@redhat.com>
Date:	Sun, 28 Feb 2010 12:49:14 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Johannes Weiner <hannes@...xchg.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Minchan Kim <minchan.kim@...il.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: mm: used-once mapped file page detection

On 02/26/2010 09:32 AM, Johannes Weiner wrote:
> On Wed, Feb 24, 2010 at 01:39:46PM -0800, Andrew Morton wrote:
>> On Mon, 22 Feb 2010 20:49:07 +0100 Johannes Weiner<hannes@...xchg.org>  wrote:
>>
>>> This patch makes the VM be more careful about activating mapped file
>>> pages in the first place.  The minimum granted lifetime without
>>> another memory access becomes an inactive list cycle instead of the
>>> full memory cycle, which is more natural given the mentioned loads.
>>
>> iirc from a long time ago, the insta-activation of mapped pages was
>> done because people were getting peeved about having their interactive
>> applications (X, browser, etc) getting paged out, and bumping the pages
>> immediately was found to help with this subjective problem.
>>
>> So it was a latency issue more than a throughput issue.  I wouldn't be
>> surprised if we get some complaints from people for the same reasons as
>> a result of this patch.
>
> Agreed.  Although we now have other things in place to protect them once
> they are active (VM_EXEC protection, lazy active list scanning).

You think we'll need VM_EXEC protection on the inactive list
after your changes?

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