From db33ec371be8e45956e8cebb5b0fe641f008430b Mon Sep 17 00:00:00 2001 From: Konstantin Khlebnikov Date: Sun, 7 Jun 2020 21:42:55 -0700 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] Signed-off-by: Konstantin Khlebnikov Signed-off-by: Andrew Morton Acked-by: Michal Hocko Cc: Roman Gushchin Cc: Randy Dunlap Link: http://lkml.kernel.org/r/158894738928.208854.5244393925922074518.stgit@buzz Signed-off-by: Linus Torvalds --- Documentation/admin-guide/cgroup-v2.rst | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-) (limited to 'Documentation/admin-guide') diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst index c2a4b652bd1a..ce3e05e41724 100644 --- a/Documentation/admin-guide/cgroup-v2.rst +++ b/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. - This event is not raised if the OOM killer is not considered as an option, e.g. for failed high-order - allocations. + allocations or if caller asked to not retry attempts. oom_kill The number of processes belonging to this cgroup -- cgit v1.2.3