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| -rw-r--r-- | Documentation/admin-guide/cgroup-v2.rst | 28 |
1 files changed, 13 insertions, 15 deletions
diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst index b0dda10b9382..7b56ca80e37a 100644 --- a/Documentation/admin-guide/cgroup-v2.rst +++ b/Documentation/admin-guide/cgroup-v2.rst @@ -1005,10 +1005,17 @@ 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. @@ -1950,17 +1957,8 @@ 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. |