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Tue, 28 Mar 2023 10:43:40 -0700 (PDT) Date: Tue, 28 Mar 2023 13:43:39 -0400 From: Johannes Weiner To: Yosry Ahmed Cc: Tejun Heo , Josef Bacik , Jens Axboe , Zefan Li , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , Michal =?iso-8859-1?Q?Koutn=FD?= , Vasily Averin , cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org Subject: Re: [PATCH v1 3/9] memcg: do not flush stats in irq context Message-ID: References: <20230328061638.203420-1-yosryahmed@google.com> <20230328061638.203420-4-yosryahmed@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230328061638.203420-4-yosryahmed@google.com> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: D2A1310000B X-Stat-Signature: idzdtyia4yifo3iy3aas5swejqy8gxji X-Rspam-User: X-HE-Tag: 1680025421-717220 X-HE-Meta: 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 tKb4TMaQ 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 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 Tue, Mar 28, 2023 at 06:16:32AM +0000, Yosry Ahmed wrote: > Currently, the only context in which we can invoke an rstat flush from > irq context is through mem_cgroup_usage() on the root memcg when called > from memcg_check_events(). An rstat flush is an expensive operation that > should not be done in irq context, so do not flush stats and use the > stale stats in this case. > > Arguably, usage threshold events are not reliable on the root memcg > anyway since its usage is ill-defined. > > Suggested-by: Johannes Weiner > Suggested-by: Shakeel Butt > Signed-off-by: Yosry Ahmed Excellent, thanks! Acked-by: Johannes Weiner