linux-kernel - Re: [PATCH 2/3] mm: memcg: add a helper for non-unified stats flushing

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Message-ID: <5y3e32ek6owren3q5e3gzonzxzdhs53ihywj3mtbhz56hnizfy@fctafygsnfaq>
Date:   Tue, 22 Aug 2023 18:35:00 +0200
From:   Michal Koutný <mkoutny@...e.com>
To:     Yosry Ahmed <yosryahmed@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Shakeel Butt <shakeelb@...gle.com>,
        Muchun Song <muchun.song@...ux.dev>,
        Ivan Babrou <ivan@...udflare.com>, Tejun Heo <tj@...nel.org>,
        linux-mm@...ck.org, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] mm: memcg: add a helper for non-unified stats
 flushing

On Tue, Aug 22, 2023 at 09:00:06AM -0700, Yosry Ahmed <yosryahmed@...gle.com> wrote:
> We can probably also kick FLUSH_TIME forward as well.

True, they guard same work.

> Perhaps I can move both into do_stats_flush() then. If I understand
> correctly this is what you mean?

Yes.

> What do you think?

The latter is certainly better looking code.

I wasn't sure at first about moving stats_flush_threshold reset before
actual flush but on second thought it should not be a significant change
- readers: may skip flushing, the values that they read should still be
  below the error threshold,
- writers: may be slowed down a bit (because of conditional atomic write
  optimization in memcg_rstat_updates), presumably not on average
  though.

So the latter should work too.

Michal

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