linux-kernel - Re: [PATCH v17 1/7] mm: support madvise(MADV

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Message-ID: <54D50A87.8000902@redhat.com>
Date:	Fri, 06 Feb 2015 13:40:07 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Shaohua Li <shli@...nel.org>, Michal Hocko <mhocko@...e.cz>
CC:	Minchan Kim <minchan@...nel.org>,
	"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-api@...r.kernel.org, Hugh Dickins <hughd@...gle.com>,
	Johannes Weiner <hannes@...xchg.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Mel Gorman <mgorman@...e.de>, Jason Evans <je@...com>,
	zhangyanfei@...fujitsu.com,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH v17 1/7] mm: support madvise(MADV_FREE)

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On 02/06/2015 01:32 PM, Shaohua Li wrote:
> On Fri, Feb 06, 2015 at 01:58:25PM +0100, Michal Hocko wrote:
>> On Thu 05-02-15 16:33:11, Shaohua Li wrote: [...]
>>> Did you think about move the MADV_FREE pages to the head of
>>> inactive LRU, so they can be reclaimed easily?
>> 
>> Yes this makes sense for pages living on the active LRU list. I
>> would preserve LRU ordering on the inactive list because there is
>> no good reason to make the operation more costly for inactive
>> pages. On the other hand having tons of to-be-freed pages on the
>> active list clearly sucks. Care to send a patch?
> 
> Considering anon pages are in active LRU first, it's likely
> MADV_FREE pages are in active list. I'm curious why preserves the
> order of inactive list.

Only before the first time MADV_FREE is called on those pages.

If a program repeatedly allocates and frees the same memory
region, not moving the MADV_FREE pages around in the LRU
several times can save some overhead.

- -- 
All rights reversed
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