linux-kernel - Re: [LKP] [mm] 3484b2de949: -46.2% aim7.jobs-per-min

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Date:	Sat, 28 Feb 2015 01:46:42 +0000
From:	Mel Gorman <mgorman@...e.de>
To:	Huang Ying <ying.huang@...ux.intel.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, LKP ML <lkp@...org>
Subject: Re: [LKP] [mm] 3484b2de949: -46.2% aim7.jobs-per-min

On Fri, Feb 27, 2015 at 03:21:36PM +0800, Huang Ying wrote:
> FYI, we noticed the below changes on
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> commit 3484b2de9499df23c4604a513b36f96326ae81ad ("mm: rearrange zone fields into read-only, page alloc, statistics and page reclaim lines")
> 
> The perf cpu-cycles for spinlock (zone->lock) increased a lot.  I suspect there are some cache ping-pong or false sharing.
> 

Are you sure about this result? I ran similar tests here and found that
there was a major regression introduced near there but it was commit
05b843012335 ("mm: memcontrol: use root_mem_cgroup res_counter") that
cause the problem and it was later reverted.  On local tests on a 4-node
machine, commit 3484b2de9499df23c4604a513b36f96326ae81ad was within 1%
of the previous commit and well within the noise.

-- 
Mel Gorman
SUSE Labs
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