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From: Shakeel Butt To: Roman Gushchin Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Muchun Song , Harry Yoo , Qi Zheng , Vlastimil Babka , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Meta kernel team Subject: Re: [PATCH 0/4] memcg: cleanup the memcg stats interfaces Message-ID: References: <20251110232008.1352063-1-shakeel.butt@linux.dev> <87pl9oqtpg.fsf@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87pl9oqtpg.fsf@linux.dev> X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: 9C71B1C0007 X-Stat-Signature: 7d5454yx3izgm75udgdfq8phfdb8wk48 X-Rspamd-Server: rspam02 X-Rspam-User: X-HE-Tag: 1762889659-283086 X-HE-Meta: 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 GLKvePvd 3f2VAIt6+/75Fy29VWY4OiMCkR0zB4+IdZCXnZm9hT0Y/r1MHpWw/zTG8vHgy4/f01ErBojJ/CzdzzdaIw3yUe9UBMnXKFcPN7CVggdDsxm+oWI/tpfVSEK7KenG1CMJ3+BU4WdOGMBUvDyKsbsIWD0AR2nk2kGQJzm8eRNgurtj9GwEJEVgVqQbhXHvSvdPc2BbfQCBAPoPR82OpGEDmGrIK0A== 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 Tue, Nov 11, 2025 at 11:01:47AM -0800, Roman Gushchin wrote: > Shakeel Butt writes: > > > The memcg stats are safe against irq (and nmi) context and thus does not > > require disabling irqs. However for some stats which are also maintained > > at node level, it is using irq unsafe interface and thus requiring the > > users to still disables irqs or use interfaces which explicitly disables > > irqs. Let's move memcg code to use irq safe node level stats function > > which is already optimized for architectures with HAVE_CMPXCHG_LOCAL > > (all major ones), so there will not be any performance penalty for its > > usage. > > Do you have any production data for this or it's theory-based? At the moment it is theory-based or more specifically based on the comments on HAVE_CMPXCHG_LOCAL variants of stats update functions. > > In general I feel we need a benchmark focused on memcg stats: > there was a number of performance improvements and regressions in this > code over last years, so a dedicated benchmark can help with measuring > them. Yeah it makes sense to have a benchmark. Let me see which benchmark trigger this code paths a lot. At the high level, these interfaces are used in reclaim and migration which are not really that performance critical. I will try benchmarks with a lot of allocs/frees. > > Nice cleanup btw, thanks! Thanks.