linux-kernel - Re: [PATCH] mm: use pagevec to rotate reclaimable page

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Message-Id: <200709181129.50253.nickpiggin@yahoo.com.au>
Date:	Tue, 18 Sep 2007 11:29:50 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Hisashi Hifumi <hifumi.hisashi@....ntt.co.jp>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] mm: use pagevec to rotate reclaimable page

On Tuesday 18 September 2007 20:41, Hisashi Hifumi wrote:
> I modified my patch based on your comment.
>
> At 11:37 07/09/14, Andrew Morton wrote:
>  >So I do think that for safety and sanity's sake, we should be taking a
>  > ref on the pages when they are in a pagevec.  That's going to hurt your
>  > nice performance numbers :(
>
> I did ping test again to observe performance deterioration caused by taking
> a ref.
>
> 	-2.6.23-rc6-with-modifiedpatch
> 	--- testmachine ping statistics ---
> 	3000 packets transmitted, 3000 received, 0% packet loss, time 53386ms
> 	rtt min/avg/max/mdev = 0.074/0.110/4.716/0.147 ms, pipe 2, ipg/ewma
> 17.801/0.129 ms
>
> The result for my original patch is as follows.
>
> 	-2.6.23-rc5-with-originalpatch
> 	--- testmachine ping statistics ---
> 	3000 packets transmitted, 3000 received, 0% packet loss, time 51924ms
> 	rtt min/avg/max/mdev = 0.072/0.108/3.884/0.114 ms, pipe 2, ipg/ewma
> 17.314/0.091 ms
>
>
> The influence to response was small.

It would be interesting to test -mm kernels. They have a patch which reduces
zone lock contention quite a lot.

I think your patch is a nice idea, and with less zone lock contention in other
areas, it is possible that it might produce a relatively larger improvement.
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