linux-kernel - Re: mapped pagecache pages vs unmapped pages

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Message-Id: <8041334015453@webcorp4.yandex-team.ru>
Date:	Tue, 10 Apr 2012 03:50:53 +0400
From:	Alexey Ivanov <rbtz@...dex-team.ru>
To:	Rik van Riel <riel@...hat.com>
Cc:	"gnehzuil.lzheng@...il.com" <gnehzuil.lzheng@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>, yinghan@...gle.com
Subject: Re: mapped pagecache pages vs unmapped pages

Did you consider making this ratio tunable, at least manually(i.e. via sysctl)?
I suppose we are not the only ones with almost-whole-ram-mmaped workload.

09.04.2012, 22:56, "Rik van Riel" <riel@...hat.com>:
> On 04/09/2012 01:11 PM, Alexey Ivanov wrote:
>
>>  Thanks for the hint!
>>
>>  Can anyone clarify the reason of not using zone->inactive_ratio in inactive_file_is_low_global()?
>
> New anonymous pages start out on the active anon list, and
> are always referenced.  If memory fills up, they may end
> up getting moved to the inactive anon list; being referenced
> while on the inactive anon list is enough to get them promoted
> back to the active list.
>
> New file pages start out on the INACTIVE file list, and
> start their lives not referenced at all. Due to readahead
> extra reads, many file pages may never be referenced.
>
> Only file pages that are referenced twice make it onto
> the active list.
>
> This means the inactive file list has to be large enough
> for all the readahead buffers, and give pages enough time
> on the list that frequently accessed ones can get accessed
> twice and promoted.
>
> http://linux-mm.org/PageReplacementDesign
>
> --
> All rights reversed

-- 
Alexey Ivanov
Yandex Search Admin Team
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