[v2 PATCH 1/5] doc: memcontrol: fix the obsolete content about force empty

From: Yang Shi
Date: Fri Jan 04 2019 - 19:23:20 EST

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

Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
Documentation/cgroup-v1/memory.txt | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/Documentation/cgroup-v1/memory.txt b/Documentation/cgroup-v1/memory.txt
index 3682e99..8e2cb1d 100644
--- a/Documentation/cgroup-v1/memory.txt
+++ b/Documentation/cgroup-v1/memory.txt
@@ -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