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Sat, 02 Nov 2019 16:55:38 -0700 (PDT) Received: from [2620:15c:17:3:3a5:23a7:5e32:4598] ([2620:15c:17:3:3a5:23a7:5e32:4598]) by smtp.gmail.com with ESMTPSA id c66sm11767706pfb.25.2019.11.02.16.55.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 02 Nov 2019 16:55:38 -0700 (PDT) Date: Sat, 2 Nov 2019 16:55:37 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Konstantin Khlebnikov cc: linux-mm@kvack.org, Andrew Morton , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Michal Hocko Subject: Re: [PATCH] mm/memcontrol: update documentation about invoking oom killer In-Reply-To: <157270779336.1961.6528158720593572480.stgit@buzz> Message-ID: References: <157270779336.1961.6528158720593572480.stgit@buzz> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII 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: On Sat, 2 Nov 2019, Konstantin Khlebnikov wrote: > Since commit 29ef680ae7c2 ("memcg, oom: move out_of_memory back to the > charge path") memcg invokes oom killer not only for user page-faults. > This means 0-order allocation will either succeed or task get killed. > > Fixes: 8e675f7af507 ("mm/oom_kill: count global and memory cgroup oom kills") > Signed-off-by: Konstantin Khlebnikov > --- > Documentation/admin-guide/cgroup-v2.rst | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst > index 5361ebec3361..eb47815e137b 100644 > --- a/Documentation/admin-guide/cgroup-v2.rst > +++ b/Documentation/admin-guide/cgroup-v2.rst > @@ -1219,8 +1219,13 @@ PAGE_SIZE multiple when read back. > > Failed allocation in its turn could be returned into > userspace as -ENOMEM or silently ignored in cases like > - disk readahead. For now OOM in memory cgroup kills > - tasks iff shortage has happened inside page fault. > + disk readahead. > + > + Before 4.19 OOM in memory cgroup killed tasks iff > + shortage has happened inside page fault, random > + syscall may fail with ENOMEM or EFAULT. Since 4.19 > + failed memory cgroup allocation invokes oom killer and > + keeps retrying until it succeeds. > > This event is not raised if the OOM killer is not > considered as an option, e.g. for failed high-order The previous text is obviously incorrect for today's kernels, but I'm curious if we should be conflating the documentation here by describing the pre-4.19 behavior. OOM killing no longer happens only on page fault so maybe better to document the exact behavior today and not attempt to describe differences with previous versions?