Refine cgroup v2 docs after latest memory.low changes. Signed-off-by: Roman Gushchin <guro@xxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx> Cc: Tejun Heo <tj@xxxxxxxxxx> Cc: kernel-team@xxxxxx Cc: linux-mm@xxxxxxxxx Cc: cgroups@xxxxxxxxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx Cc: linux-doc@xxxxxxxxxxxxxxx --- 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 -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
