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[86.5.41.89]) by smtp.gmail.com with ESMTPSA id y2sm8806139wrn.31.2020.11.26.03.02.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Nov 2020 03:02:21 -0800 (PST) Date: Thu, 26 Nov 2020 11:02:20 +0000 From: Aaron Tomlin To: Michal Hocko Cc: linux-kernel , hannes@cmpxchg.org, vdavydov.dev@gmail.com, Andrew Morton , cgroups@vger.kernel.org, linux-mm Subject: Re: [PATCH] memcg: add support to generate the total count of children from root Message-ID: <20201126110220.k4o6s32er5jy2mdk@ava.usersys.com> X-PGP-Key: http://pgp.mit.edu/pks/lookup?search=atomlin%40redhat.com X-PGP-Fingerprint: 7906 84EB FA8A 9638 8D1E 6E9B E2DE 9658 19CC 77D6 References: <20201124105836.713371-1-atomlin@redhat.com> <20201124112612.GV27488@dhcp22.suse.cz> <20201124133644.GA31550@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 2020-11-24 13:47 +0000, Aaron Tomlin wrote: > On Tue, 24 Nov 2020 at 13:36, Michal Hocko wrote: > > This like any other user visible interface would be a much easier sell > > if there was a clear usecase to justify it. I do not see anything > > controversial about exporting such a value but my general take is that > > we are only adding new interface when existing ones are insufficient. A > > performance might be a very good reason but that would really require to > > come with some real life numbers. Michal, > Fair enough and understood. > > At this stage, I unfortunately do not have such supporting data. This was only > useful in an isolated situation. Having said this, I thought that the > aforementioned interface would be helpful to others, in particular, given the > known limitation. Furthermore, I can see that this is already provided via /proc/cgroups (see proc_cgroupstats_show()). As such, another possibility: the proposed interface could reliably produce the difference between the maximum permitted memory-controlled cgroup count and the used count (i.e. the remaining memory cgroup count, from root); albeit, I doubt that this would be particularly useful to others i.e., the use-case would be rather limited. Kind regards, -- Aaron Tomlin