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Date: Wed, 17 Aug 2016 18:42:54 +0200
From: Michal Hocko <mhocko@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>, Minchan Kim <minchan@kernel.org>,
        Vladimir Davydov <vdavydov@virtuozzo.com>,
        Dave Chinner <david@fromorbit.com>,
        Johannes Weiner <hannes@cmpxchg.org>, Vlastimil Babka <vbabka@suse.cz>,
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        Bob Peterson <rpeterso@redhat.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        "Huang, Ying" <ying.huang@intel.com>, Christoph Hellwig <hch@lst.de>,
        Wu Fengguang <fengguang.wu@intel.com>, LKP <lkp@01.org>,
        Tejun Heo <tj@kernel.org>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [LKP] [lkp] [xfs] 68a9f5e700: aim7.jobs-per-min -13.6% regression
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On Wed 17-08-16 17:48:25, Michal Hocko wrote:
[...]
> I will try to catch up with the rest of the email thread but from a
> quick glance it just feels like we are doing more more work under the
> lock.

Hmm, so it doesn't seem to be more work in __remove_mapping as pointed
out in http://lkml.kernel.org/r/20160816220250.GI16044@dastard

As Mel already pointed out the LRU will be basically single mapping for
this workload so any subtle change in timing might make a difference.
I was looking through 4.6..4.7 and one thing that has changed is the
inactive vs. active LRU size ratio. See 59dc76b0d4df ("mm: vmscan:
reduce size of inactive file list"). The machine has quite a lot of
memory and so the LRUs will be large as well so I guess this could have
change the timing somehow, but it feels like a wild guess so I would be
careful to blame this commit...
-- 
Michal Hocko
SUSE Labs