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bh=96IRGBfcr5J9/GRtulzalfsCYmkGXye7ZPp+1XPMemc=; b=6MDAtvpSGwX3LK8O9qM1rOGpWAdregiwBXM834bZT+hHzwDlXrMJVn1CmhFvgADN+kr0eE bkUty+OqNRYsoI3LmBMyz99GhbjJPooYX3tUQD7Act1twNH27nSwLQ4oV43AgXT4sootm6 8HC2TaWerhTJ/FZ3eGFsw0f8l9gwddk= X-Rspam-User: X-Rspamd-Queue-Id: BE502140053 X-Rspamd-Server: rspam12 X-Stat-Signature: 7kyopw6bj7jwi8kgsxuw5i8b8jzqus1p Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=ZaLX9vwl; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf26.hostedemail.com: domain of ryncsn@gmail.com designates 209.85.214.169 as permitted sender) smtp.mailfrom=ryncsn@gmail.com X-HE-Tag: 1661845515-618325 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: Michal Hocko =E4=BA=8E2022=E5=B9=B48=E6=9C=8830=E6=97=A5= =E5=91=A8=E4=BA=8C 15:12=E5=86=99=E9=81=93=EF=BC=9A > > On Tue 30-08-22 15:06:57, Kairui Song wrote: > > Michal Hocko =E4=BA=8E2022=E5=B9=B48=E6=9C=8830=E6=97= =A5=E5=91=A8=E4=BA=8C 14:45=E5=86=99=E9=81=93=EF=BC=9A > > > > > > On Tue 30-08-22 13:59:48, Kairui Song wrote: > > > > From: Kairui Song > > > > > > > > There are currently two helpers for checking if cgroup kmem > > > > accounting is enabled: > > > > > > > > - mem_cgroup_kmem_disabled > > > > - memcg_kmem_enabled > > > > > > Yes, this is a bit confusing indeed! > > > > > > > mem_cgroup_kmem_disabled is a simple helper that returns true if > > > > cgroup.memory=3Dnokmem is specified, otherwise returns false. > > > > > > > > memcg_kmem_enabled is a bit different, it returns true if > > > > cgroup.memory=3Dnokmem is not specified and there is at least one > > > > non-root cgroup ever created. And once there is any non-root memcg > > > > created, it won't go back to return false again. > > > > > > > > This may help improve performance for some corner use cases where > > > > the user enables memory cgroup and kmem accounting globally but nev= er > > > > create any cgroup. > > > > > > > > Considering that corner case is rare, especially nowadays cgroup is > > > > widely used as a standard way to organize services. > > > > > > Is it really that rare? Most configurations would use a default setup= , so > > > both MEMCG enabled and without nokmem on cmd line yet the memory > > > controller is not enabled in their setups. > > > > Actually I don't have too much confidence saying that as well... but > > AFAIK, almost all distros will create a few sub cgroup on boot by the > > init (eg. openrc, finit, systemd). > > Yeah, but do they enable the memory controller as well? Unless I am > missing something this will require at least one memcg enabled cgroup to > be created. Systemd enable memory controller by default since ver 238 from 2018, but I'm not sure about the others. Now I think I was wrong about the assumption, will be sure to do more homework next time. And thanks for the review!