linux-kernel - Re: [PATCH] memcg: cleanup racy sum avoidance code

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Message-ID: <YQDCkeFxSnh2GR7I@carbon.dhcp.thefacebook.com>
Date:   Tue, 27 Jul 2021 19:36:01 -0700
From:   Roman Gushchin <guro@...com>
To:     Shakeel Butt <shakeelb@...gle.com>
CC:     Michal Hocko <mhocko@...e.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        <cgroups@...r.kernel.org>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] memcg: cleanup racy sum avoidance code

On Tue, Jul 27, 2021 at 06:22:43PM -0700, Shakeel Butt wrote:
> We used to have per-cpu memcg and lruvec stats and the readers have to
> traverse and sum the stats from each cpu. This summing was racy and may
> expose transient negative values. So, an explicit check was added to
> avoid such scenarios. Now these stats are moved to rstat infrastructure
> and are no more per-cpu, so we can remove the fixup for transient
> negative values.
> 
> Signed-off-by: Shakeel Butt <shakeelb@...gle.com>

Acked-by: Roman Gushchin <guro@...com>

Thanks!