On Mon, Apr 28, 2014 at 02:26:44PM +0200, Michal Hocko wrote: > Be explicit about global and hard limit reclaims in our documentation. > > Signed-off-by: Michal Hocko <mho...@suse.cz> > --- > Documentation/cgroups/memory.txt | 31 +++++++++++++++++-------------- > 1 file changed, 17 insertions(+), 14 deletions(-) > > diff --git a/Documentation/cgroups/memory.txt > b/Documentation/cgroups/memory.txt > index 4937e6fff9b4..add1be001416 100644 > --- a/Documentation/cgroups/memory.txt > +++ b/Documentation/cgroups/memory.txt > @@ -236,23 +236,26 @@ it by cgroup. > 2.5 Reclaim > > Each cgroup maintains a per cgroup LRU which has the same structure as > -global VM. When a cgroup goes over its limit, we first try > -to reclaim memory from the cgroup so as to make space for the new > -pages that the cgroup has touched. If the reclaim is unsuccessful, > -an OOM routine is invoked to select and kill the bulkiest task in the > -cgroup. (See 10. OOM Control below.) > - > -The reclaim algorithm has not been modified for cgroups, except that > -pages that are selected for reclaiming come from the per-cgroup LRU > -list. > - > -NOTE: Reclaim does not work for the root cgroup, since we cannot set any > -limits on the root cgroup. > +global VM. Cgroups can get reclaimed basically under two conditions > + - under global memory pressure when all cgroups are reclaimed > + proportionally wrt. their LRU size in a round robin fashion > + - when a cgroup or its hierarchical parent (see 6. Hierarchical support) > + hits hard limit. If the reclaim is unsuccessful, an OOM routine is invoked > + to select and kill the bulkiest task in the cgroup. (See 10. OOM Control > + below.)
In the whole hierarchy, not just that cgroup. > +Global and hard-limit reclaims share the same code the only difference > +is the objective of the reclaim. The global reclaim aims at balancing > +zones' watermarks while the limit reclaim frees some memory to allow new > +charges. This is a kswapd vs. direct reclaim issue, not global vs. memcg. Memcg reclaim just happens to be direct reclaim. Either way, I'd rather not have such implementation details in the user documentation. > +NOTE: Hard limit reclaim does not work for the root cgroup, since we cannot > set > +any limits on the root cgroup. Not sure it's necessary to include this... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
