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Thu, 09 Apr 2020 10:50:46 -0700 (PDT) Received: from localhost ([2620:10d:c092:180::1:9ebe]) by smtp.gmail.com with ESMTPSA id c4sm4720748wmb.5.2020.04.09.10.50.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 09 Apr 2020 10:50:45 -0700 (PDT) Date: Thu, 9 Apr 2020 18:50:44 +0100 From: Chris Down To: Bruno =?iso-8859-1?Q?Pr=E9mont?= Cc: Michal Hocko , cgroups@vger.kernel.org, linux-mm@kvack.org, Johannes Weiner , Vladimir Davydov Subject: Re: Memory CG and 5.1 to 5.6 uprade slows backup Message-ID: <20200409175044.GC1040020@chrisdown.name> References: <20200409112505.2e1fc150@hemera.lan.sysophe.eu> <20200409094615.GE18386@dhcp22.suse.cz> <20200409121733.1a5ba17c@hemera.lan.sysophe.eu> <20200409103400.GF18386@dhcp22.suse.cz> <20200409170926.182354c3@hemera.lan.sysophe.eu> <20200409152417.GB1040020@chrisdown.name> <20200409174042.2a3389ba@hemera.lan.sysophe.eu> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Disposition: inline In-Reply-To: <20200409174042.2a3389ba@hemera.lan.sysophe.eu> Content-Transfer-Encoding: quoted-printable 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: Bruno Pr=E9mont writes: >On Thu, 9 Apr 2020 16:24:17 +0100 wrote: > >> Bruno Pr=E9mont writes: >> >Could it be that cache is being prevented from being reclaimed by a t= ask >> >in another cgroup? >> > >> >e.g. >> > cgroup/system/backup >> > first reads $files (reads each once) >> > cgroup/workload/bla >> > second&more reads $files >> > >> >Would $files remain associated to cgroup/system/backup and not >> >reclaimed there instead of being reassigned to cgroup/workload/bla? >> >> Yes, that's entirely possible. The first cgroup to fault in the pages = is >> charged for the memory. Other cgroups may use them, but they are not a= ccounted >> for as part of that other cgroup. They may also still be "active" as a= result >> of use by another cgroup. > >But the memory would then be 'active' in the original cgroup? which is >not the case here I feel. Yes, that's correct. I don't think it's the case here (since active_file = is not=20 that large in the affected cgroup), but it's certainly generally a possib= ility.