linux-kernel - Re: [PATCH 1/1] mm, oom_adj: don't loop through tasks in __set_oom

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Message-ID: <20200820162645.GP5033@dhcp22.suse.cz>
Date:   Thu, 20 Aug 2020 18:26:45 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Suren Baghdasaryan <surenb@...gle.com>
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Tim Murray <timmurray@...gle.com>, mingo@...nel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>, esyr@...hat.com,
        christian@...lner.me, areber@...hat.com,
        Shakeel Butt <shakeelb@...gle.com>, cyphar@...har.com,
        Oleg Nesterov <oleg@...hat.com>, adobriyan@...il.com,
        Andrew Morton <akpm@...ux-foundation.org>,
        gladkov.alexey@...il.com, Michel Lespinasse <walken@...gle.com>,
        daniel.m.jordan@...cle.com, avagin@...il.com,
        bernd.edlinger@...mail.de,
        John Johansen <john.johansen@...onical.com>,
        laoar.shao@...il.com, Minchan Kim <minchan@...nel.org>,
        kernel-team <kernel-team@...roid.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org, linux-mm <linux-mm@...ck.org>
Subject: Re: [PATCH 1/1] mm, oom_adj: don't loop through tasks in
 __set_oom_adj when not necessary

On Thu 20-08-20 08:56:53, Suren Baghdasaryan wrote:
[...]
> Catching up on the discussion which was going on while I was asleep...
> So it sounds like there is a consensus that oom_adj should be moved to
> mm_struct rather than trying to synchronize it among tasks sharing mm.
> That sounds reasonable to me too. Michal answered all the earlier
> questions about this patch, so I won't be reiterating them, thanks
> Michal. If any questions are still lingering about the original patch
> I'll be glad to answer them.

I think it still makes some sense to go with a simpler (aka less tricky)
solution which would be your original patch with an incremental fix for
vfork and the proper ordering (http://lkml.kernel.org/r/20200820124109.GI5033@dhcp22.suse.cz)
and then make a more complex shift to mm struct on top of that. The
former will be less tricky to backport to stable IMHO.
-- 
Michal Hocko
SUSE Labs