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doc: cgroup: update note about conditions when oom killer is invoked 

Starting from v4.19 commit 29ef680ae7 ("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 <khlebnikov@yandex-team.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Link: http://lkml.kernel.org/r/158894738928.208854.5244393925922074518.stgit@buzz
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Konstantin Khlebnikov 2020-06-07 21:42:55 -07:00 committed by Linus Torvalds
parent 490741ab1b
commit db33ec371b
1 changed files with 8 additions and 9 deletions
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17
Documentation/admin-guide/cgroup-v2.rst
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@ -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