From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: [patch 54/54] doc: cgroup: update note about conditions when oom killer is invoked Date: Sun, 07 Jun 2020 21:42:55 -0700 Message-ID: <20200608044255.Jspt1z7ML%akpm@linux-foundation.org> References: <20200607212615.b050e41fac139a1e16fe00bd@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from mail.kernel.org ([198.145.29.99]:39450 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726929AbgFHEm4 (ORCPT ); Mon, 8 Jun 2020 00:42:56 -0400 In-Reply-To: <20200607212615.b050e41fac139a1e16fe00bd@linux-foundation.org> Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: akpm@linux-foundation.org, guro@fb.com, khlebnikov@yandex-team.ru, linux-mm@kvack.org, mhocko@suse.com, mm-commits@vger.kernel.org, rdunlap@infradead.org, torvalds@linux-foundation.org From: Konstantin Khlebnikov Subject: doc: cgroup: update note about conditions when oom killer is invoked Starting from v4.19 commit 29ef680ae7c2 ("memcg, oom: move out_of_memory back to the charge path") cgroup oom killer is no longer invoked only from page faults. Now it implements the same semantics as global OOM killer: allocation context invokes OOM killer and keeps retrying until success. [akpm@linux-foundation.org: fixes per Randy] Link: http://lkml.kernel.org/r/158894738928.208854.5244393925922074518.stgit@buzz Signed-off-by: Konstantin Khlebnikov Acked-by: Michal Hocko Cc: Roman Gushchin Cc: Randy Dunlap Signed-off-by: Andrew Morton --- Documentation/admin-guide/cgroup-v2.rst | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-) --- a/Documentation/admin-guide/cgroup-v2.rst~doc-cgroup-update-note-about-conditions-when-oom-killer-is-invoked +++ a/Documentation/admin-guide/cgroup-v2.rst @@ -1170,6 +1170,13 @@ PAGE_SIZE multiple when read back. Under certain circumstances, the usage may go over the limit temporarily. + In default configuration regular 0-order allocations always + succeed unless OOM killer chooses current task as a victim. + + Some kinds of allocations don't invoke the OOM killer. + Caller could retry them differently, return into userspace + as -ENOMEM or silently ignore in cases like disk readahead. + This is the ultimate protection mechanism. As long as the high limit is used and monitored properly, this limit's utility is limited to providing the final safety net. @@ -1226,17 +1233,9 @@ PAGE_SIZE multiple when read back. The number of time the cgroup's memory usage was reached the limit and allocation was about to fail. - Depending on context result could be invocation of OOM - killer and retrying allocation or failing allocation. - - 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.