linux-kernel - Re: [PATCH] kswapd: avoid unnecessary rebalance after an unsuccessful balancing

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Message-ID: <4E32FA3D.5060100@draigBrady.com>
Date:	Fri, 29 Jul 2011 19:21:49 +0100
From:	Pádraig Brady <P@...igBrady.com>
To:	Alex Shi <alex.shi@...el.com>
CC:	linux-mm@...ck.org, mgorman@...e.de, linux-kernel@...r.kernel.org,
	andrea@...share.com, tim.c.chen@...el.com, shaohua.li@...el.com,
	akpm@...ux-foundation.org, riel@...hat.com, luto@....edu
Subject: Re: [PATCH] kswapd: avoid unnecessary rebalance after an unsuccessful
 balancing

On 07/29/2011 04:23 PM, Alex Shi wrote:
> In commit 215ddd66, Mel Gorman said kswapd is better to sleep after a
> unsuccessful balancing if there is tighter reclaim request pending in
> the balancing. In this scenario, the 'order' and 'classzone_idx'
> that are checked for tighter request judgment is incorrect, since they
> aren't the one kswapd should read from new pgdat, but the last time pgdat
> value for just now balancing. Then kswapd will skip try_to_sleep func
> and rebalance the last pgdat request. It's not our expected behavior.
> 
> So, I added new variables to distinguish the returned order/classzone_idx
> from last balancing, that can resolved above issue in that scenario.
> 
> I tested the patch on our LKP system with swap-cp/fio mmap randrw
> benchmarks. The performance has no change.
> 
> Padraig Brady, would you like to test this patch for your scenario.

This
+ your previous 2 line patch
+ Mel's 3 patches
+ 2.6.38.4

still works fine for me.

cheers,
Pádraig.
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