From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roman Gushchin Subject: [v11 6/6] mm, oom, docs: describe the cgroup-aware OOM killer Date: Thu, 5 Oct 2017 14:04:54 +0100 Message-ID: <20171005130454.5590-7-guro@fb.com> References: <20171005130454.5590-1-guro@fb.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-type; s=facebook; bh=CmrXeXt3KZUA2oaEEW2kw+ZTtpKE65GsU9ihFRLVXno=; b=Lg8o6HaLimbp7DCgCiaJ6twmwJPnlZEt0OEz3wSrmSvnU6JSR3bFi5TDVs07c1+WP/rc UcAoU4l2fYJwcOM2KjmMEgy3RHF2ObJS9F/7Ai/g5c6BdgCJeTbJ+mTUT3fU7f2VtI7D sWMwj76wODm98MDIY0o89LyoQToa9PgX3Ts= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.onmicrosoft.com; s=selector1-fb-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version; bh=CmrXeXt3KZUA2oaEEW2kw+ZTtpKE65GsU9ihFRLVXno=; b=TWhb7vU5nSqeIRaz09a6C9efVYGTCzpITVbpiD1PcBpodKERD4nlmPvbboewOSJn9tHP2LooUSCrZIqgrhNTJv5NIFUyt4NOptzEO2gcPA5Y4B/tJ+QGMVIAYkiPX+8afm9z0z9xyMIwuj4F6+TWPxA4LIKRs3F8Sxm3fRrT2Eo= In-Reply-To: <20171005130454.5590-1-guro@fb.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-mm@kvack.org Cc: Roman Gushchin , Michal Hocko , Vladimir Davydov , Johannes Weiner , Tetsuo Handa , Andrew Morton , David Rientjes , Tejun Heo , kernel-team@fb.com, cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Document the cgroup-aware OOM killer. Signed-off-by: Roman Gushchin Cc: Michal Hocko Cc: Vladimir Davydov Cc: Johannes Weiner Cc: Tetsuo Handa Cc: Andrew Morton Cc: David Rientjes Cc: Tejun Heo Cc: kernel-team@fb.com Cc: cgroups@vger.kernel.org Cc: linux-doc@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org --- Documentation/cgroup-v2.txt | 51 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 51 insertions(+) diff --git a/Documentation/cgroup-v2.txt b/Documentation/cgroup-v2.txt index 3f8216912df0..28429e62b0ea 100644 --- a/Documentation/cgroup-v2.txt +++ b/Documentation/cgroup-v2.txt @@ -48,6 +48,7 @@ v1 is available under Documentation/cgroup-v1/. 5-2-1. Memory Interface Files 5-2-2. Usage Guidelines 5-2-3. Memory Ownership + 5-2-4. OOM Killer 5-3. IO 5-3-1. IO Interface Files 5-3-2. Writeback @@ -1043,6 +1044,28 @@ PAGE_SIZE multiple when read back. high limit is used and monitored properly, this limit's utility is limited to providing the final safety net. + memory.oom_group + + A read-write single value file which exists on non-root + cgroups. The default is "0". + + If set, OOM killer will consider the memory cgroup as an + indivisible memory consumers and compare it with other memory + consumers by it's memory footprint. + If such memory cgroup is selected as an OOM victim, all + processes belonging to it or it's descendants will be killed. + + This applies to system-wide OOM conditions and reaching + the hard memory limit of the cgroup and their ancestor. + If OOM condition happens in a descendant cgroup with it's own + memory limit, the memory cgroup can't be considered + as an OOM victim, and OOM killer will not kill all belonging + tasks. + + Also, OOM killer respects the /proc/pid/oom_score_adj value -1000, + and will never kill the unkillable task, even if memory.oom_group + is set. + memory.events A read-only flat-keyed file which exists on non-root cgroups. The following entries are defined. Unless specified @@ -1246,6 +1269,34 @@ to be accessed repeatedly by other cgroups, it may make sense to use POSIX_FADV_DONTNEED to relinquish the ownership of memory areas belonging to the affected files to ensure correct memory ownership. +OOM Killer +~~~~~~~~~~ + +Cgroup v2 memory controller implements a cgroup-aware OOM killer. +It means that it treats cgroups as first class OOM entities. + +Under OOM conditions the memory controller tries to make the best +choice of a victim, looking for a memory cgroup with the largest +memory footprint, considering leaf cgroups and cgroups with the +memory.oom_group option set, which are considered to be an indivisible +memory consumers. + +By default, OOM killer will kill the biggest task in the selected +memory cgroup. A user can change this behavior by enabling +the per-cgroup memory.oom_group option. If set, it causes +the OOM killer to kill all processes attached to the cgroup, +except processes with oom_score_adj set to -1000. + +This affects both system- and cgroup-wide OOMs. For a cgroup-wide OOM +the memory controller considers only cgroups belonging to the sub-tree +of the OOM'ing cgroup. + +The root cgroup is treated as a leaf memory cgroup, so it's compared +with other leaf memory cgroups and cgroups with oom_group option set. + +If there are no cgroups with the enabled memory controller, +the OOM killer is using the "traditional" process-based approach. + IO -- -- 2.13.6