linux-kernel - Re: OOM detection regressions since 4.7

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Message-ID: <20160822105441.GH13596@dhcp22.suse.cz>
Date:   Mon, 22 Aug 2016 12:54:41 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Markus Trippelsdorf <markus@...ppelsdorf.de>,
        Arkadiusz Miskiewicz <a.miskiewicz@...il.com>,
        Ralf-Peter Rohbeck <Ralf-Peter.Rohbeck@...ntum.com>,
        Jiri Slaby <jslaby@...e.com>, Olaf Hering <olaf@...fle.de>,
        Vlastimil Babka <vbabka@...e.cz>,
        Joonsoo Kim <js1304@...il.com>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: OOM detection regressions since 4.7

On Mon 22-08-16 06:05:28, Greg KH wrote:
> On Mon, Aug 22, 2016 at 11:37:07AM +0200, Michal Hocko wrote:
[...]
> > > From 899b738538de41295839dca2090a774bdd17acd2 Mon Sep 17 00:00:00 2001
> > > From: Michal Hocko <mhocko@...e.com>
> > > Date: Mon, 22 Aug 2016 10:52:06 +0200
> > > Subject: [PATCH] mm, oom: prevent pre-mature OOM killer invocation for high
> > >  order request
> > > 
> > > There have been several reports about pre-mature OOM killer invocation
> > > in 4.7 kernel when order-2 allocation request (for the kernel stack)
> > > invoked OOM killer even during basic workloads (light IO or even kernel
> > > compile on some filesystems). In all reported cases the memory is
> > > fragmented and there are no order-2+ pages available. There is usually
> > > a large amount of slab memory (usually dentries/inodes) and further
> > > debugging has shown that there are way too many unmovable blocks which
> > > are skipped during the compaction. Multiple reporters have confirmed that
> > > the current linux-next which includes [1] and [2] helped and OOMs are
> > > not reproducible anymore. A simpler fix for the stable is to simply
> > > ignore the compaction feedback and retry as long as there is a reclaim
> > > progress for high order requests which we used to do before. We already
> > > do that for CONFING_COMPACTION=n so let's reuse the same code when
> > > compaction is enabled as well.
> > > 
> > > [1] http://lkml.kernel.org/r/20160810091226.6709-1-vbabka@suse.cz
> > > [2] http://lkml.kernel.org/r/f7a9ea9d-bb88-bfd6-e340-3a933559305a@suse.cz
> > > 
> > > Fixes: 0a0337e0d1d1 ("mm, oom: rework oom detection")
> > > Signed-off-by: Michal Hocko <mhocko@...e.com>
> > > ---
> > >  mm/page_alloc.c | 50 ++------------------------------------------------
> > >  1 file changed, 2 insertions(+), 48 deletions(-)
> 
> So, if this goes into Linus's tree, can you let stable@...r.kernel.org
> know about it so we can add it to the 4.7-stable tree?  Otherwise
> there's not much I can do here now, right?

My plan would be actually to not push this to Linus because we have a
proper fix for Linus tree. It is just that the fix is quite large and I
felt like the stable should get the most simple fix possible, which is
this partial revert. So, what I am trying to tell is to push a non-linus
patch to stable as it is simpler.
-- 
Michal Hocko
SUSE Labs