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Wed, 22 Mar 2023 22:08:22 -0700 (PDT) MIME-Version: 1.0 References: <20230323040037.2389095-1-yosryahmed@google.com> In-Reply-To: From: Yosry Ahmed Date: Wed, 22 Mar 2023 22:07:43 -0700 Message-ID: Subject: Re: [RFC PATCH 0/7] Make rstat flushing IRQ and sleep friendly To: Shakeel Butt Cc: Tejun Heo , Josef Bacik , Jens Axboe , Zefan Li , Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Andrew Morton , 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-Server: rspam05 X-Rspamd-Queue-Id: 9FAD3180004 X-Stat-Signature: n8dh9n3jk5jiqy9uh7zukuthpxcqptz1 X-Rspam-User: X-HE-Tag: 1679548104-735434 X-HE-Meta: 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 4kpkZJs3 XcDNnqIloF798NJSoR80TAXh0igUkj+1whEFun1Xe9kkNRvePVotvSpUByWKqEyfyWnCoYZjBNjlxb7ULP5egfHb1PdYFGtOfbz+AVpv282NYnufmKkK+PMlMDfIyeI4Bp/oEXxco9yn/v0wNcBlUDx7SyuiEbRdJgIkNvVKeRIQItcOFU8MZDPB5sjSDcrRcS5BigZUtYfHcOtjd9JvKa22s3yH30dadmQr3S8MJoRlDHLq9T3UZ6G2mq8fPhxrKcEOA4d42Yjr9zYQ= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000039, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Mar 22, 2023 at 9:10=E2=80=AFPM Shakeel Butt = wrote: > > On Wed, Mar 22, 2023 at 9:00=E2=80=AFPM Yosry Ahmed wrote: > > > > Currently, if rstat flushing is invoked using the irqsafe variant > > cgroup_rstat_flush_irqsafe(), we keep interrupts disabled and do not > > sleep for the entire flush operation, which is O(# cpus * # cgroups). > > This can be rather dangerous. > > > > Not all contexts that use cgroup_rstat_flush_irqsafe() actually cannot > > sleep, and among those that cannot sleep, not all contexts require > > interrupts to be disabled. > > Too many negations in the above sentence is making it very confusing. Sorry, this is indeed very confusing. I guess a better rephrasing is: Multiple code paths use cgroup_rstat_flush_irqsafe(), but many of them can sleep. Even among the code paths that actually cannot sleep, multiple ones are interruptible.