I like the approach in general but see the comments bellow:
On Mon 10-09-12 15:33:55, Tejun Heo wrote:
[...]
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3855,12 +3855,17 @@ static int mem_cgroup_hierarchy_write(st
> */
> if ((!parent_memcg || !parent_memcg->use_hierarchy) &&
> (val == 1 || val == 0)) {
> - if (list_empty(&cont->children))
> + if (list_empty(&cont->children)) {
> memcg->use_hierarchy = val;
> - else
> + /* we're fully hierarchical iff root uses hierarchy */
> + if (mem_cgroup_is_root(memcg))
> + mem_cgroup_subsys.broken_hierarchy = !val;
> + } else {
> retval = -EBUSY;
> - } else
> + }
> + } else {
> retval = -EINVAL;
> + }
>
> out:
> cgroup_unlock();
> @@ -4953,6 +4958,7 @@ mem_cgroup_create(struct cgroup *cont)
> &per_cpu(memcg_stock, cpu);
> INIT_WORK(&stock->work, drain_local_stock);
> }
> + mem_cgroup_subsys.broken_hierarchy = !memcg->use_hierarchy;
Hmmm, this will warn even if we have
root (default use_hierarchy=0)
\
A (use_hierarchy=1)
\
B <- here
which is unfortunate because it will add a noise to a reasonable
configuration.
I think this is fixable if you move the warning after
cgroup_subsys_state::create and broken_hierarchy would be set only if
parent is not root and use_hierarchy==0 in mem_cgroup_create. Something
like:
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 795e525..d5c93ab 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4973,6 +4973,13 @@ mem_cgroup_create(struct cgroup *cont)
} else {
res_counter_init(&memcg->res, NULL);
res_counter_init(&memcg->memsw, NULL);
+ /*
+ * Deeper hierachy with use_hierarchy == false doesn't make
+ * much sense so let cgroup subsystem know about this
unfortunate
+ * state in our controller.
+ */
+ if (parent && parent != root_mem_cgroup)
+ mem_cgroup_subsys.broken_hierarchy = true;
}
memcg->last_scanned_node = MAX_NUMNODES;
INIT_LIST_HEAD(&memcg->oom_notify);
What do you think?
> hotcpu_notifier(memcg_cpu_hotplug_callback, 0);
> } else {
> parent = mem_cgroup_from_cont(cont->parent);
> --- a/net/core/netprio_cgroup.c
> +++ b/net/core/netprio_cgroup.c
> @@ -330,7 +330,17 @@ struct cgroup_subsys net_prio_subsys = {
> .subsys_id = net_prio_subsys_id,
> #endif
> .base_cftypes = ss_files,
> - .module = THIS_MODULE
> + .module = THIS_MODULE,
> +
> + /*
> + * net_prio has artificial limit on the number of cgroups and
> + * disallows nesting making it impossible to co-mount it with other
> + * hierarchical subsystems. Remove the artificially low PRIOIDX_SZ
> + * limit and properly nest configuration such that children follow
> + * their parents' configurations by default and are allowed to
> + * override and remove the following.
> + */
> + .broken_hierarchy = trye,
typo
--
Michal Hocko
SUSE Labs
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