linux-kernel - Re: [PATCH v2 5/6] mm: flush memcg percpu stats and events before releasing

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Message-ID: <20190313160017.GA31891@cmpxchg.org>
Date:   Wed, 13 Mar 2019 12:00:17 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Roman Gushchin <guroan@...il.com>
Cc:     linux-mm@...ck.org, kernel-team@...com,
        linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>,
        Rik van Riel <riel@...riel.com>,
        Michal Hocko <mhocko@...nel.org>, Roman Gushchin <guro@...com>
Subject: Re: [PATCH v2 5/6] mm: flush memcg percpu stats and events before
 releasing

On Tue, Mar 12, 2019 at 03:34:02PM -0700, Roman Gushchin wrote:
> Flush percpu stats and events data to corresponding before releasing
> percpu memory.
> 
> Although per-cpu stats are never exactly precise, dropping them on
> floor regularly may lead to an accumulation of an error. So, it's
> safer to flush them before releasing.
> 
> To minimize the number of atomic updates, let's sum all stats/events
> on all cpus locally, and then make a single update per entry.
> 
> Signed-off-by: Roman Gushchin <guro@...com>

Acked-by: Johannes Weiner <hannes@...xchg.org>

Do you mind merging 6/6 into this one? That would make it easier to
verify that the code added in this patch and the code removed in 6/6
are indeed functionally equivalent.