On Tue 13-11-12 08:14:42, Tejun Heo wrote:
> On Tue, Nov 13, 2012 at 04:30:36PM +0100, Michal Hocko wrote:
> > @@ -1063,8 +1063,8 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
> > struct mem_cgroup *prev,
> > struct mem_cgroup_reclaim_cookie *reclaim)
> > {
> > - struct mem_cgroup *memcg = NULL;
> > - int id = 0;
> > + struct mem_cgroup *memcg = NULL,
> > + *last_visited = NULL;
>
> Nitpick but please don't do this.
OK, will make it grep friendlier;
> > + /*
> > + * Root is not visited by cgroup iterators so it needs a special
> > + * treatment.
> > + */
> > + if (!last_visited) {
> > + css = &root->css;
> > + } else {
> > + struct cgroup *next_cgroup;
> > +
> > + next_cgroup = cgroup_next_descendant_pre(
> > + last_visited->css.cgroup,
> > + root->css.cgroup);
> > + if (next_cgroup)
> > + css = cgroup_subsys_state(next_cgroup,
> > + mem_cgroup_subsys_id);
>
> Hmmm... wouldn't it be better to move the reclaim logic into a
> function and do the following?
>
> reclaim(root);
> for_each_descendent_pre()
> reclaim(descendant);
We cannot do for_each_descendent_pre here because we do not iterate
through the whole hierarchy all the time. Check shrink_zone.
> If this is a problem, I'd be happy to add a iterator which includes
> the top node.
This would help with the above if-else but I do not think this is the
worst thing in the function ;)
> I'd prefer controllers not using the next functions directly.
Well, we will need to use it directly because of the single group
reclaim mentioned above.
--
Michal Hocko
SUSE Labs
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