linux-kernel - Re: [PATCH v4 4/7] Reclaim invalidated page ASAP

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Date:	Tue, 14 Dec 2010 11:34:11 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Ben Gamari <bgamari.foss@...il.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Nick Piggin <npiggin@...nel.dk>
Subject: Re: [PATCH v4 4/7] Reclaim invalidated page ASAP

On Tue, Dec 14, 2010 at 11:07 AM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@...fujitsu.com> wrote:
> On Tue, 14 Dec 2010 00:31:05 +0900
> Minchan Kim <minchan.kim@...il.com> wrote:
>
>> Test Environment :
>> DRAM : 2G, CPU : Intel(R) Core(TM)2 CPU
>> Rsync backup directory size : 16G
>>
>> rsync version is 3.0.7.
>> rsync patch is Ben's fadivse.
>> stress scenario do following jobs with parallel.
>>
>> 1. make all -j4 linux, git clone linux-kernel
>> 2. git clone linux-kernel
>> 3. rsync src dst
>>
>> nrns : no-patched rsync + no stress
>> prns : patched rsync + no stress
>> nrs  : no-patched rsync + stress
>> prs  : patched rsync + stress
>>
>> pginvalidate : the number of dirty/writeback pages which is invalidated by fadvise
>> pgreclaim : pages moved PG_reclaim trick in inactive's tail
>>
>> In summary, my patch enhances a littie bit about elapsed time in
>> memory pressure environment and enhance reclaim effectivness(reclaim/reclaim)
>> with x2. It means reclaim latency is short and doesn't evict working set
>> pages due to invalidated pages.
>>
>> Look at reclaim effectivness. Patched rsync enhances x2 about reclaim
>> effectiveness and compared to mmotm-12-03, mmotm-12-03-fadvise enhances
>> 3 minute about elapsed time in stress environment.
>> I think it's due to reduce scanning, reclaim overhead.
>>
>> In no-stress enviroment, fadivse makes program little bit slow.
>> I think because there are many pgfault. I don't know why it happens.
>> Could you guess why it happens?
>>
>> Before futher work, I hope listen opinions.
>> Any comment is welcome.
>>
>
> At first, the improvement seems great. Thank you for your effort.

Thanks, Kame.

>
>> In no-stress enviroment, fadivse makes program little bit slow.
>> I think because there are many pgfault. I don't know why it happens.
>> Could you guess why it happens?
>>
>
> Are there no program which accesses a directory rsync'ed ?

Maybe. some programs might have mmaped files.
But although it happens, deactivate_page found that and it does
nothing so the page can't be reclaimed.

>
> Thanks,
> -Kame
>
>



-- 
Kind regards,
Minchan Kim
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