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[141.239.149.160]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-70b7ec7ecb2sm6709689b3a.103.2024.07.16.12.53.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 Jul 2024 12:53:59 -0700 (PDT) Date: Tue, 16 Jul 2024 09:53:57 -1000 From: Tejun Heo To: Roman Gushchin Cc: Michal Hocko , David Finkel , Muchun Song , Andrew Morton , core-services@vimeo.com, Jonathan Corbet , Shakeel Butt , Shuah Khan , Johannes Weiner , Zefan Li , cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH] mm, memcg: cg2 memory{.swap,}.peak write handlers Message-ID: References: <20240715203625.1462309-1-davidf@vimeo.com> <20240715203625.1462309-2-davidf@vimeo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: E7F384001A X-Stat-Signature: yefwwdkxe6zjc361aefemb3oaegeuozx X-HE-Tag: 1721159640-198767 X-HE-Meta: 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 Axlsrb0h mi3SvfHvwbYQkBEvBehtPO9Q8ju4D6GZyGvXNXC5LsvSLxoFQds2RhSvME0Qf26ZUg/AGZc9qQ4uGmBE4XnyplzPukqD2ZCMdxe67OTSuAAq7DukZ6iYRiztE4uusVdves3DQWRcayAnNz6gnoRpseDR1hMBZ3rflj50/zKnVCKvGv1Z+zVzdoFLhGV0VO8ghUxKAxsE9DrgrqVyktd/79nzkihvfMo4847KBYzB53W9f650M39EVRBrTSrECA44Nhvg8Ui/ziWitgcMFy/vQSlYGKSif/RbL/m3/lYceUsskr5Pzi27Xk/zZlUR4LXnmUzRCcw03feiwx4d7RKHbzyBUeHjZdOEEI3HycoTgPSZKWoWWi/hzkE35l8iEKH2l1SZU8CYJ0QkjThsvHJ3+Y/MKm9Joujo+aanu8T/c3ozAHO/U4U1n58GPW+ldoylwMcF2 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: Hello, On Tue, Jul 16, 2024 at 05:01:15PM +0000, Roman Gushchin wrote: > > If we want to allow peak measurement of time periods, I wonder whether we > > could do something similar to pressure triggers - ie. let users register > > watchers so that each user can define their own watch periods. This is more > > involved but more useful and less error-inducing than adding reset to a > > single counter. > > It's definitely a better user interface and I totally agree with you regarding > the shortcomings of the proposed interface with a global reset. But if you let > users to register a (potentially large) number of watchers, it might be quite > bad for the overall performance, isn't it? To mitigate it, we'll need to reduce > the accuracy of peak values. And then the question is why not just poll it > periodically from userspace? I haven't thought in detail but it's the same problem that PSI triggers have, right? PSI seems to have found a reasonable trade-off across accuracy, overhead and usage restrictions? Maybe peak usage isn't as widely useful and it doesn't justify to engineer something as sophisticated. I don't know. Thanks. -- tejun