linux-kernel - Re: [PATCH] vmscan: retry without cache trim mode if nothing scanned

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Message-ID: <YE6TVtA2EuagQAtj@slm.duckdns.org>
Date:   Sun, 14 Mar 2021 18:51:02 -0400
From:   Tejun Heo <tj@...nel.org>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     "Huang, Ying" <ying.huang@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Mel Gorman <mgorman@...e.de>,
        Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Michal Hocko <mhocko@...e.cz>,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH] vmscan: retry without cache trim mode if nothing scanned

Hello,

On Sun, Mar 14, 2021 at 01:58:33PM -0700, Shakeel Butt wrote:
> > If my understanding were correct, what Tejun suggested is to add a fast
> > read interface to rstat to be used in hot path.  And its accuracy is
> > similar as that of traditional per-CPU counter.  But if we can regularly
> > update the lruvec rstat with something like vmstat_update(), that should
> > be OK for the issue described in this patch.
> >
> 
> This is also my understanding. Tejun, please correct us if we misunderstood you.

Yeah, that was what I had on mind. Instead of always flushing on read, have
a variant where flushing is explicit and trigger that periodically (or
whichever way appropriate).

Thanks.

-- 
tejun