linux-kernel - Re: [RFC 0/1] add support for reclaiming priorities per mem cgroup

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Message-ID: <20170413160343.GC29727@cmpxchg.org>
Date:   Thu, 13 Apr 2017 12:03:43 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     Tim Murray <timmurray@...gle.com>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        LKML <linux-kernel@...r.kernel.org>, cgroups@...r.kernel.org,
        Linux MM <linux-mm@...ck.org>, surenb@...gle.com,
        totte@...gle.com, kernel-team@...roid.com
Subject: Re: [RFC 0/1] add support for reclaiming priorities per mem cgroup

On Thu, Mar 30, 2017 at 09:48:55AM -0700, Shakeel Butt wrote:
> > A more useful metric for memory pressure at this point is quantifying
> > that time you spend thrashing: time the job spends in direct reclaim
> > and on the flipside time the job waits for recently evicted pages to
> > come back. Combined, that gives you a good measure of overhead from
> > memory pressure; putting that in relation to a useful baseline of
> > meaningful work done gives you a portable scale of how effictively
> > your job is running.
> >
> > I'm working on that right now, hopefully I'll have something useful
> > soon.
> 
> Johannes, is the work you are doing only about file pages or will it
> equally apply to anon pages as well?

It will work on both, with the caveat that *any* swapin is counted as
memory delay, whereas only cache misses of recently evicted entries
count toward it (we don't have timestamped shadow entries for anon).