On Wed, Apr 16, 2014 at 02:34:25PM -0700, Andrew Morton wrote: > On Wed, 16 Apr 2014 17:13:18 -0400 Johannes Weiner <hannes@xxxxxxxxxxx> wrote: > > > Per-memcg swappiness and oom killing can currently not be tweaked on a > > memcg that is part of a hierarchy, but not the root of that hierarchy. > > Users have complained that they can't configure this when they turned > > on hierarchy mode. In fact, with hierarchy mode becoming the default, > > this restriction disables the tunables entirely. > > > > But there is no good reason for this restriction. The settings for > > swappiness and OOM killing are taken from whatever memcg whose limit > > triggered reclaim and OOM invocation, regardless of its position in > > the hierarchy tree. > > > > Allow setting swappiness on any group. The knob on the root memcg > > already reads the global VM swappiness, make it writable as well. > > > > Allow disabling the OOM killer on any non-root memcg. > > Documentation/cgroups/memory.txt needs updates? Yes, that makes sense, thanks. How about this? --- Subject: [patch] mm: memcontrol: remove hierarchy restrictions for swappiness and oom_control fix Update Documentation/cgroups/memory.txt Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx> --- diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt index 2622115276aa..1829c65f8371 100644 --- a/Documentation/cgroups/memory.txt +++ b/Documentation/cgroups/memory.txt @@ -535,17 +535,15 @@ Note: 5.3 swappiness -Similar to /proc/sys/vm/swappiness, but affecting a hierarchy of groups only. +Similar to /proc/sys/vm/swappiness, but only affecting reclaim that is +triggered by this cgroup's hard limit. The tunable in the root cgroup +corresponds to the global swappiness setting. + Please note that unlike the global swappiness, memcg knob set to 0 really prevents from any swapping even if there is a swap storage available. This might lead to memcg OOM killer if there are no file pages to reclaim. -Following cgroups' swappiness can't be changed. -- root cgroup (uses /proc/sys/vm/swappiness). -- a cgroup which uses hierarchy and it has other cgroup(s) below it. -- a cgroup which uses hierarchy and not the root of hierarchy. - 5.4 failcnt A memory cgroup provides memory.failcnt and memory.memsw.failcnt files. @@ -754,7 +752,6 @@ You can disable the OOM-killer by writing "1" to memory.oom_control file, as: #echo 1 > memory.oom_control -This operation is only allowed to the top cgroup of a sub-hierarchy. If OOM-killer is disabled, tasks under cgroup will hang/sleep in memory cgroup's OOM-waitqueue when they request accountable memory. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>