doc: memcontrol: fix the obsolete content about force empty

We don't do page cache reparent anymore when offlining memcg, so update
force empty related content accordingly.

Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Yang Shi 2019-01-16 07:51:35 +08:00 committed by Jonathan Corbet
parent b631c7f513
commit 053bc56938

View File

@ -70,7 +70,7 @@ Brief summary of control files.
memory.soft_limit_in_bytes # set/show soft limit of memory usage
memory.stat # show various statistics
memory.use_hierarchy # set/show hierarchical account enabled
memory.force_empty # trigger forced move charge to parent
memory.force_empty # trigger forced page reclaim
memory.pressure_level # set memory pressure notifications
memory.swappiness # set/show swappiness parameter of vmscan
(See sysctl's vm.swappiness)
@ -459,8 +459,9 @@ About use_hierarchy, see Section 6.
the cgroup will be reclaimed and as many pages reclaimed as possible.
The typical use case for this interface is before calling rmdir().
Because rmdir() moves all pages to parent, some out-of-use page caches can be
moved to the parent. If you want to avoid that, force_empty will be useful.
Though rmdir() offlines memcg, but the memcg may still stay there due to
charged file caches. Some out-of-use page caches may keep charged until
memory pressure happens. If you want to avoid that, force_empty will be useful.
Also, note that when memory.kmem.limit_in_bytes is set the charges due to
kernel pages will still be seen. This is not considered a failure and the