On Mon 29-02-16 20:16:33, Vladimir Davydov wrote: > When a cgroup directory is removed, the memory cgroup subsys state does > not disappear immediately. Instead, it's left hanging around until the > last reference to it is gone, which implies reclaiming all pages from > its lruvec. > > In the unified hierarchy, there's the memory.low knob, which can be used > to set a best-effort protection for a memory cgroup - the reclaimer > first scans those cgroups whose consumption is above memory.low, and > only if it fails to reclaim enough pages, it gets to the rest. > > Currently this protection is not reset when the cgroup directory is > removed. As a result, if a dead memory cgroup has a lot of page cache > charged to it and a high value of memory.low, it will result in higher > pressure exerted on live cgroups, and userspace will have no ways to > detect such consumers and reconfigure memory.low properly. > > To fix this, let's reset memory.low on css offline. Makes sense to me > Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> > --- > mm/memcontrol.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index ae8b81c55685..ab7bfe870c7d 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -4214,6 +4214,8 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css) > > memcg_offline_kmem(memcg); > wb_memcg_offline(memcg); > + > + memcg->low = 0; > } > > static void mem_cgroup_css_released(struct cgroup_subsys_state *css) > -- > 2.1.4 -- Michal Hocko SUSE Labs -- 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>