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

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Date:   Wed, 13 Sep 2017 07:52:02 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Mikulas Patocka <mpatocka@...hat.com>,
        Michal Hocko <mhocko@...nel.org>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Johannes Weiner <hannes@...xchg.org>,
        Mel Gorman <mgorman@...e.de>,
        Dave Hansen <dave.hansen@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: respect the __GFP_NOWARN flag when warning about stalls

>
> We would have to consider (instead of jiffies) the time the process was
> either running, or waiting on something that's related to memory
> allocation/reclaim (page lock etc.). I.e. deduct the time the process
> was runable but there was no available cpu. I expect however that such
> level of detail wouldn't be feasible here, though?
>

Johannes' memdelay work (once merged) might be useful here. I think
memdalay can differentiate between an allocating process getting
delayed due to preemption or due to unsuccessful reclaim/compaction.
If the delay is due to unsuccessful reclaim/compaction then we should
warn here.