On Tue 22-05-18 14:25:27, Roman Gushchin wrote:
> Explicitly propagate effective memory min/low values down by the tree.
>
> If there is the global memory pressure, it's not really necessary.
> Effective memory guarantees will be propagated automatically
> as we traverse memory cgroup tree in the reclaim path.
>
> But if there is no global memory pressure, effective memory protection
> still matters for local (memcg-scoped) memory pressure.
> So, we have to update effective limits in the subtree,
> if a user changes memory.min and memory.low values.
Please be explicit about the exact problem. Ideally with a memcg tree example.
> Signed-off-by: Roman Gushchin <guro@xxxxxx>
> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxxxx>
> Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
> Cc: Greg Thelen <gthelen@xxxxxxxxxx>
> Cc: Tejun Heo <tj@xxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> ---
> mm/memcontrol.c | 14 ++++++++++++--
> 1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index ab5673dbfc4e..b9cd0bb63759 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -5374,7 +5374,7 @@ static int memory_min_show(struct seq_file *m, void *v)
> static ssize_t memory_min_write(struct kernfs_open_file *of,
> char *buf, size_t nbytes, loff_t off)
> {
> - struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
> + struct mem_cgroup *iter, *memcg = mem_cgroup_from_css(of_css(of));
> unsigned long min;
> int err;
>
> @@ -5385,6 +5385,11 @@ static ssize_t memory_min_write(struct kernfs_open_file *of,
>
> page_counter_set_min(&memcg->memory, min);
>
> + rcu_read_lock();
> + for_each_mem_cgroup_tree(iter, memcg)
> + mem_cgroup_protected(NULL, iter);
> + rcu_read_unlock();
> +
> return nbytes;
> }
>
> @@ -5404,7 +5409,7 @@ static int memory_low_show(struct seq_file *m, void *v)
> static ssize_t memory_low_write(struct kernfs_open_file *of,
> char *buf, size_t nbytes, loff_t off)
> {
> - struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
> + struct mem_cgroup *iter, *memcg = mem_cgroup_from_css(of_css(of));
> unsigned long low;
> int err;
>
> @@ -5415,6 +5420,11 @@ static ssize_t memory_low_write(struct kernfs_open_file *of,
>
> page_counter_set_low(&memcg->memory, low);
>
> + rcu_read_lock();
> + for_each_mem_cgroup_tree(iter, memcg)
> + mem_cgroup_protected(NULL, iter);
> + rcu_read_unlock();
> +
> return nbytes;
> }
>
> --
> 2.14.3
--
Michal Hocko
SUSE Labs
