Messages in this thread | | | Date | Fri, 16 Jan 2009 09:29:48 +0800 | From | Li Zefan <> | Subject | Re: [PATCH 3/4] memcg: hierarchical reclaim by CSS ID |
| |
> /* > - * Dance down the hierarchy if needed to reclaim memory. We remember the > - * last child we reclaimed from, so that we don't end up penalizing > - * one child extensively based on its position in the children list. > + * Visit the first child (need not be the first child as per the ordering > + * of the cgroup list, since we track last_scanned_child) of @mem and use > + * that to reclaim free pages from. > + */ > +static struct mem_cgroup * > +mem_cgroup_select_victim(struct mem_cgroup *root_mem) > +{ > + struct mem_cgroup *ret = NULL; > + struct cgroup_subsys_state *css; > + int nextid, found; > + > + if (!root_mem->use_hierarchy) { > + spin_lock(&root_mem->reclaim_param_lock); > + root_mem->scan_age++; > + spin_unlock(&root_mem->reclaim_param_lock); > + css_get(&root_mem->css); > + ret = root_mem; > + } > + > + while (!ret) { > + rcu_read_lock(); > + nextid = root_mem->last_scanned_child + 1; > + css = css_get_next(&mem_cgroup_subsys, nextid, &root_mem->css, > + &found); > + if (css && css_is_populated(css) && css_tryget(css))
I don't see why you need to check css_is_populated(css) ?
> + ret = container_of(css, struct mem_cgroup, css); > + > + rcu_read_unlock(); > + /* Updates scanning parameter */ > + spin_lock(&root_mem->reclaim_param_lock); > + if (!css) { > + /* this means start scan from ID:1 */ > + root_mem->last_scanned_child = 0; > + root_mem->scan_age++; > + } else > + root_mem->last_scanned_child = found; > + spin_unlock(&root_mem->reclaim_param_lock); > + } > + > + return ret; > +} > +
| |