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Thu, 30 Mar 2023 00:43:12 -0700 (PDT) MIME-Version: 1.0 References: <20230328221644.803272-1-yosryahmed@google.com> <20230328221644.803272-8-yosryahmed@google.com> In-Reply-To: From: Yosry Ahmed Date: Thu, 30 Mar 2023 00:42:36 -0700 Message-ID: Subject: Re: [PATCH v2 7/9] workingset: memcg: sleep when flushing stats in workingset_refault() To: Michal Hocko Cc: Tejun Heo , Josef Bacik , Jens Axboe , Zefan Li , Johannes Weiner , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , =?UTF-8?Q?Michal_Koutn=C3=BD?= , Vasily Averin , cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 226051C0017 X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: b6t4j5po5f5ujsexdbsdmkbhbsgycx5s X-HE-Tag: 1680162193-690009 X-HE-Meta: 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 1pDSbd6a hxZxWXbAaeORbTfEx2oOosVup4En7BM4fqPfdvpri3y+JM+RIQvn8suZnQpOkBYWlNlk+ErbALwSmmSYFMwq8WGgrO0WIEhPoZHNFF5aW9GsMkhBJXyUh0D6e48yFgD1AtRjeJ9AyMxcgd5dsqvWgRQuIVK13ZqfhKGj7XNwPFySsW0tXIGgoWXi7S/BAFFiMWnVrQDngzziSSoK7i12xinJP+7x6YdntHY6zTwSnC1e5Mvrb5Y37lcIqpgr4y2jwIQEqyd/M6r7pZDSxXBh1qKYb/pg6zAh5dL1R0oqDCtwYQ+pOEjTaQnIwr7aS7XGv3f4NKeszMTPL/zdvxPfAGG4Wf8Z9GXBv5r0U X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Mar 30, 2023 at 12:39=E2=80=AFAM Michal Hocko wro= te: > > On Tue 28-03-23 22:16:42, Yosry Ahmed wrote: > > In workingset_refault(), we call > > mem_cgroup_flush_stats_atomic_ratelimited() to flush stats within an > > RCU read section and with sleeping disallowed. Move the call above > > the RCU read section and allow sleeping to avoid unnecessarily > > performing a lot of work without sleeping. > > Could you say few words why the flushing is done before counters are > updated rather than after (the RCU section)? It's not about the counters that are updated, it's about the counters that we read. Stats readers do a flush first to read accurate stats. We flush before a read, not after an update. > -- > Michal Hocko > SUSE Labs