linux-kernel - Re: [PATCH] mm, memcg: reclaim more aggressively before high allocator throttling

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Message-ID: <20200521132120.GR6462@dhcp22.suse.cz>
Date:   Thu, 21 May 2020 15:21:20 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Chris Down <chris@...isdown.name>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Tejun Heo <tj@...nel.org>, linux-mm@...ck.org,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com
Subject: Re: [PATCH] mm, memcg: reclaim more aggressively before high
 allocator throttling

On Thu 21-05-20 13:57:59, Chris Down wrote:
> Michal Hocko writes:
> > > A cgroup is a unit and breaking it down into "reclaim fairness" for
> > > individual tasks like this seems suspect to me. For example, if one task in
> > > a cgroup is leaking unreclaimable memory like crazy, everyone in that cgroup
> > > is going to be penalised by allocator throttling as a result, even if they
> > > aren't "responsible" for that reclaim.
> > 
> > You are right, but that doesn't mean that it is desirable that some
> > tasks would be throttled unexpectedly too long because of the other's activity.
> 
> Are you really talking about throttling, or reclaim? If throttling, tasks
> are already throttled proportionally to how much this allocation is
> contributing to the overage in calculate_high_delay.

Reclaim is a part of the throttling mechanism. It is a productive side
of it actually.
 
> If you're talking about reclaim, trying to reason about whether the overage
> is the result of some other task in this cgroup or the task that's
> allocating right now is something that we already know doesn't work well
> (eg. global OOM).

I am not sure I follow you here.
-- 
Michal Hocko
SUSE Labs