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b=BzQIJgz6qwwMrNEgE2Vhlegj8TRaj5Urd1TV2M0cWusrt8kj1h6eUM7wqP3jxrq4Q TlP1+4hcS5DYeCDatHaj94lGjcyIeMEA5vTmilWisLftlfGmlu872l/7cZ51gZOJyo byDEVbcyIrEnpuIQJPrbdoG3DTrwZZGaZarGpnJdYe10VqJ0hOKHW1uPaxUak6p8Tz 6gp0SKFV2zUvlWn7RmylxzHc08M16K3edHAEwRogz6FwVA6IsY4e3kXiv4QqSX4up9 2nj9+e/2xRQeNdMUL26Zbc02CbhYblmKZHevFesrOdCIvp1E6j25PnHEkJYhowzdWg aux47erEG9FKQ== Date: Wed, 19 Mar 2025 07:26:57 -1000 From: Tejun Heo To: Mateusz Guzik Cc: Greg Thelen , Johannes Weiner , Michal =?iso-8859-1?Q?Koutn=FD?= , Andrew Morton , Eric Dumazet , Yosry Ahmed , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Eric Dumazet Subject: Re: [PATCH] cgroup/rstat: avoid disabling irqs for O(num_cpu) Message-ID: References: <20250319071330.898763-1-gthelen@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Queue-Id: 736A4180018 X-Rspamd-Server: rspam05 X-Stat-Signature: ir8kmpft8tbr65opth7gf6t55fkiafw5 X-HE-Tag: 1742405219-13490 X-HE-Meta: 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 t3LVVf+J dGlbHIvgcVXiAKFn1PXSIdXso3A2fGVXudDTu6XeKHeUF0Ovku4ClBMDMU1tlQYHUWKAVUFE+apzl6Spm+aGHKvc7M5krPb56x8Gz33l/1CJiPoRxlP4srWMUzftXpnFoOfVbc0M5lH9a/F9F6J09VP2JT/cwMF78SLXX8MmwPlfsjZV8cIPb56zDvNqtzjZfhcJDNAWk1R8KHhOQYybdbHF41NCemXZ9L7XcTnt95dwaQ68EhvEsLyt1rv6bcBjqZzMe2Rk7/SvU0y8= 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: List-Subscribe: List-Unsubscribe: On Wed, Mar 19, 2025 at 11:47:32AM +0100, Mateusz Guzik wrote: ... > Is not this going a little too far? > > the lock + irq trip is quite expensive in its own right and now is > going to be paid for each cpu, as in the total time spent executing > cgroup_rstat_flush_locked is going to go up. Lock/unlock when the cacheline is already on the cpu is pretty cheap and on modern x86 cpus at least irq on/off are also only a few cycles, so you probably wouldn't be able to tell the difference. Thanks. -- tejun