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

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Message-ID: <20200220205416.GI698990@mtj.thefacebook.com>
Date:   Thu, 20 Feb 2020 15:54:16 -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, Daniel.

On Thu, Feb 20, 2020 at 02:55:35PM -0500, Daniel Jordan wrote:
> On Thu, Feb 20, 2020 at 01:45:45PM -0500, Tejun Heo wrote:
> > 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.
> 
> I see, your last mail is clearer now.  If it's easy to do, a pointer to where
> this happens would help so we're on the same page.

Network packet rx is the clearest example I think, but you already
mentioned it. Reclaim is less so but when kswapd reclaims, it walks
everybody, and there can be a lot of small cgroups.

Thanks.

-- 
tejun