linux-kernel - Re: [PATCH] mm: memcontrol: asynchronous reclaim for memory.high

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Message-ID: <20200220184545.GH698990@mtj.thefacebook.com>
Date:   Thu, 20 Feb 2020 13:45:45 -0500
From:   Tejun Heo <tj@...nel.org>
To:     Daniel Jordan <daniel.m.jordan@...cle.com>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <guro@...com>, linux-mm@...ck.org,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com, Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] mm: memcontrol: asynchronous reclaim for memory.high

Hello,

On Thu, Feb 20, 2020 at 01:23:26PM -0500, Daniel Jordan wrote:
> The amount of work wouldn't seem to matter as long as the kernel thread stays
> in the cgroup and lives long enough.  There's only the one-time cost of
> attaching it when it's forked.  That seems doable for unbound workqueues (the
> async reclaim), but may not be for the network packets.

The setup cost can be lazy optimized but it'd still have to bounce the
tiny pieces of work to different threads instead of processing them in
one fell swoop from the same context, which most likely is gonna be
untenably expensive.

Thanks.

-- 
tejun