linux-kernel - Re: [PATCH] mm: respect the __GFP_NOWARN flag when warning about stalls

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Message-ID: <20170913143509.6wtp3pd5yhqe53ck@dhcp22.suse.cz>
Date:   Wed, 13 Sep 2017 16:35:09 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:     vbabka@...e.cz, mpatocka@...hat.com, hannes@...xchg.org,
        mgorman@...e.de, dave.hansen@...el.com, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: respect the __GFP_NOWARN flag when warning about
 stalls

On Wed 13-09-17 23:14:43, Tetsuo Handa wrote:
> Vlastimil Babka wrote:
> > On 09/13/2017 03:54 PM, Tetsuo Handa wrote:
> > > Michal Hocko wrote:
> > >> Let's see what others think about this.
> > > 
> > > Whether __GFP_NOWARN should warn about stalls is not a topic to discuss.
> > 
> > It is the topic of this thread, which tries to address a concrete
> > problem somebody has experienced. In that context, the rest of your
> > concerns seem to me not related to this problem, IMHO.
> 
> I suggested replacing warn_alloc() with safe/useful one rather than tweaking
> warn_alloc() about __GFP_NOWARN.

What you seem to ignore is that whatever method you use for reporting
stalling allocations you would still have to consider whether to dump
a stall information for __GFP_NOWARN ones. And as the current report
shows that might be a bad idea. So please stick to the topic and do not
move it towards _what_ is the proper way of stall detection.
-- 
Michal Hocko
SUSE Labs