lkml.org 
[lkml]   [2018]   [Apr]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v3 4/4] mm/docs: describe memory.low refinements
Date
Refine cgroup v2 docs after latest memory.low changes.

Signed-off-by: Roman Gushchin <guro@fb.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: kernel-team@fb.com
Cc: linux-mm@kvack.org
Cc: cgroups@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-doc@vger.kernel.org
---
Documentation/cgroup-v2.txt | 28 +++++++++++++---------------
1 file changed, 13 insertions(+), 15 deletions(-)

diff --git a/Documentation/cgroup-v2.txt b/Documentation/cgroup-v2.txt
index f728e55602b2..7ee462b8a6ac 100644
--- a/Documentation/cgroup-v2.txt
+++ b/Documentation/cgroup-v2.txt
@@ -1006,10 +1006,17 @@ PAGE_SIZE multiple when read back.
A read-write single value file which exists on non-root
cgroups. The default is "0".

- Best-effort memory protection. If the memory usages of a
- cgroup and all its ancestors are below their low boundaries,
- the cgroup's memory won't be reclaimed unless memory can be
- reclaimed from unprotected cgroups.
+ Best-effort memory protection. If the memory usage of a
+ cgroup is within its effective low boundary, the cgroup's
+ memory won't be reclaimed unless memory can be reclaimed
+ from unprotected cgroups.
+
+ Effective low boundary is limited by memory.low values of
+ all ancestor cgroups. If there is memory.low overcommitment
+ (child cgroup or cgroups are requiring more protected memory,
+ than parent will allow), then each child cgroup will get
+ the part of parent's protection proportional to the its
+ actual memory usage below memory.low.

Putting more memory than generally available under this
protection is discouraged.
@@ -2008,17 +2015,8 @@ system performance due to overreclaim, to the point where the feature
becomes self-defeating.

The memory.low boundary on the other hand is a top-down allocated
-reserve. A cgroup enjoys reclaim protection when it and all its
-ancestors are below their low boundaries, which makes delegation of
-subtrees possible. Secondly, new cgroups have no reserve per default
-and in the common case most cgroups are eligible for the preferred
-reclaim pass. This allows the new low boundary to be efficiently
-implemented with just a minor addition to the generic reclaim code,
-without the need for out-of-band data structures and reclaim passes.
-Because the generic reclaim code considers all cgroups except for the
-ones running low in the preferred first reclaim pass, overreclaim of
-individual groups is eliminated as well, resulting in much better
-overall workload performance.
+reserve. A cgroup enjoys reclaim protection when it's within its low,
+which makes delegation of subtrees possible.

The original high boundary, the hard limit, is defined as a strict
limit that can not budge, even if the OOM killer has to be called.
--
2.14.3
\
 
 \ /
  Last update: 2018-04-05 21:01    [W:0.083 / U:1.224 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site