linux-kernel - Re: [PATCH -mm] mm: more likely reclaim MADV

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Date:	Mon, 21 Jul 2008 12:53:23 +0900
From:	"KOSAKI Motohiro" <kosaki.motohiro@...fujitsu.com>
To:	"Andrew Morton" <akpm@...ux-foundation.org>
Cc:	"Johannes Weiner" <hannes@...urebad.de>,
	"Rik van Riel" <riel@...hat.com>,
	"Peter Zijlstra" <peterz@...radead.org>,
	Nossum <vegard.nossum@...il.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH -mm] mm: more likely reclaim MADV_SEQUENTIAL mappings

Hi Andrew,

>> in my experience,
>>   - page_referenced_one is performance critical point.
>>     you should test some benchmark.
>>   - its patch improved mmaped-copy performance about 5%.
>>     (Of cource, you should test in current -mm. MM code was changed widely)
>>
>> So, I'm looking for your test result :)
>
> The change seems logical and I queued it for 2.6.28.

Great.

> But yes, testing for what-does-this-improve is good and useful, but so
> is testing for what-does-this-worsen.  How do we do that in this case?

In general, page_referenced_one is important for reclaim throuput.
if crap page_referenced_one changing happend,
system reclaim throuput become slow down.

Of cource, I don't think this patch cause performance regression :-)

So, any benchmark with memcgroup memory restriction is good choice.

btw:
maybe, I will able to post mamped-copy improve mesurement of Johannes's patch
after OLS.
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