linux-kernel - Re: [PATCH 2/2] mm, oom: do not enfore OOM killer for __GFP

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Date:   Mon, 12 Dec 2016 09:52:55 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:     akpm@...ux-foundation.org, vbabka@...e.cz, hannes@...xchg.org,
        mgorman@...e.de, rientjes@...gle.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] mm, oom: do not enfore OOM killer for __GFP_NOFAIL
 automatically

On Sun 11-12-16 22:53:55, Tetsuo Handa wrote:
> Tetsuo Handa wrote:
> > Michal Hocko wrote:
> > > On Thu 08-12-16 21:53:44, Tetsuo Handa wrote:
> > > > If we could agree
> > > > with calling __alloc_pages_nowmark() before out_of_memory() if __GFP_NOFAIL
> > > > is given, we can avoid locking up while minimizing possibility of invoking
> > > > the OOM killer...
> > >
> > > I do not understand. We do __alloc_pages_nowmark even when oom is called
> > > for GFP_NOFAIL.
> > 
> > Where is that? I can find __alloc_pages_nowmark() after out_of_memory()
> > if __GFP_NOFAIL is given, but I can't find __alloc_pages_nowmark() before
> > out_of_memory() if __GFP_NOFAIL is given.
> > 
> > What I mean is below patch folded into
> > "[PATCH 1/2] mm: consolidate GFP_NOFAIL checks in the allocator slowpath".
> > 
> Oops, I wrongly implemented "__alloc_pages_nowmark() before out_of_memory() if
> __GFP_NOFAIL is given." case. Updated version is shown below.

If you want to introduce such a change then make sure to justify it
properly in the changelog. I will not comment on this change here
because I believe it is not directly needed for neither of the two
patches.
-- 
Michal Hocko
SUSE Labs