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

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Message-ID: <20190313182301.GA7336@castle.DHCP.thefacebook.com>
Date:   Wed, 13 Mar 2019 18:23:09 +0000
From:   Roman Gushchin <guro@...com>
To:     Johannes Weiner <hannes@...xchg.org>
CC:     Roman Gushchin <guroan@...il.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Kernel Team <Kernel-team@...com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Tejun Heo <tj@...nel.org>, Rik van Riel <riel@...riel.com>,
        Michal Hocko <mhocko@...nel.org>
Subject: Re: [PATCH v2 5/6] mm: flush memcg percpu stats and events before
 releasing

On Wed, Mar 13, 2019 at 12:00:17PM -0400, Johannes Weiner wrote:
> 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.
> 

I did try, but the result is the mess of added and removed lines,
which are *almost* the same, but are slightly different (e.g. tabs).
So it's much easier to review it as two separate patches.

Thanks!