From: Michal Hocko <mhocko@suse.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Muchun Song <songmuchun@bytedance.com>,
vdavydov.dev@gmail.com, akpm@linux-foundation.org,
cgroups@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: memcontrol: skip propagate percpu vmstat values to current memcg
Date: Wed, 20 Jan 2021 08:49:56 +0100 [thread overview]
Message-ID: <20210120074956.GB9371@dhcp22.suse.cz> (raw)
In-Reply-To: <YAcPwhl//jF/WpHu@cmpxchg.org>
On Tue 19-01-21 11:58:42, Johannes Weiner wrote:
> On Tue, Jan 19, 2021 at 01:27:44PM +0800, Muchun Song wrote:
> > The current memcg will be freed soon, so updating it's vmstat and
> > vmevent values is pointless. Just skip updating it.
> >
> > Signed-off-by: Muchun Song <songmuchun@bytedance.com>
>
> Oof, that's pretty subtle! Somebody trying to refactor that code for
> other purposes may not immediately notice that optimization and add
> potentially tedious bugs.
Absolutely agreed!
> How much does this save? Cgroup creation and deletion isn't really
> considered a hot path. It takes global locks and such...
This is not the first time when an (micro)optimization is posted without
any data showing benefit or otherwise appealing justification. Sigh.
--
Michal Hocko
SUSE Labs
prev parent reply other threads:[~2021-01-20 7:50 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-19 5:27 Muchun Song
2021-01-19 16:58 ` Johannes Weiner
2021-01-20 7:49 ` Michal Hocko [this message]
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