Re: [PATCH] mm: memcontrol: reset memory.low on css offline
From: Michal Hocko
Date: Mon Feb 29 2016 - 13:29:31 EST
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->low = 0;
> static void mem_cgroup_css_released(struct cgroup_subsys_state *css)