linux-kernel - [PATCH 0/2] thp nodereclaim fixes

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Date:   Tue, 25 Sep 2018 14:03:24 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
        David Rientjes <rientjes@...gle.com>,
        Andrea Argangeli <andrea@...nel.org>,
        Zi Yan <zi.yan@...rutgers.edu>,
        Stefan Priebe - Profihost AG <s.priebe@...fihost.ag>,
        "Kirill A. Shutemov" <kirill@...temov.name>, <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 0/2] thp nodereclaim fixes

Hi,
this has been brought up by Andrea [1] and he proposed two different
fixes for the regression. I have proposed an alternative fix [2]. I have
changed my mind in the end because whatever fix we end up with it should
be backported to the stable trees so going with a minimalistic one is
preferred so I have got back to the Andrea's second proposed solution
[3] in the end. I have just reworded the changelog to reflect other bug
report with the stall information.

My primary concern about [3] was that the __GFP_THISNODE logic should be
placed in alloc_hugepage_direct_gfpmask which I've done on top of the
fix as a cleanup (patch 2) and it doesn't need to be backported to the
stable tree.

I am still not happy that the David's workload will regress as a result
but we should really focus on the default behavior and come with a more
robust solution for specialized one for those who have more restrictive
NUMA preferences. I am thinking about a new numa policy that would mimic
node reclaim behavior and I am willing to work on that but we really
have to fix the regression first and that is the patch 1.

Thoughts, alternative patches?

[1] http://lkml.kernel.org/r/20180820032204.9591-1-aarcange@redhat.com
[2] http://lkml.kernel.org/r/20180830064732.GA2656@dhcp22.suse.cz
[3] http://lkml.kernel.org/r/20180820032640.9896-2-aarcange@redhat.com