On Thu, 14 Apr 2011 15:54:24 -0700
Ying Han <yinghan@google.com> wrote:

> This add the mechanism for background reclaim which we remember the
> last scanned node and always starting from the next one each time.
> The simple round-robin fasion provide the fairness between nodes for
> each memcg.
>
> changelog v4..v3:
> 1. split off from the per-memcg background reclaim patch.
>
> Signed-off-by: Ying Han <yinghan@google.com>

Yeah, looks nice. Thank you for splitting.

> ---
>  include/linux/memcontrol.h |    3 +++
>  mm/memcontrol.c            |   40 ++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 43 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index f7ffd1f..d4ff7f2 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -88,6 +88,9 @@ extern int mem_cgroup_init_kswapd(struct mem_cgroup *mem,
>                                 struct kswapd *kswapd_p);
>  extern void mem_cgroup_clear_kswapd(struct mem_cgroup *mem);
>  extern wait_queue_head_t *mem_cgroup_kswapd_wait(struct mem_cgroup *mem);
> +extern int mem_cgroup_last_scanned_node(struct mem_cgroup *mem);
> +extern int mem_cgroup_select_victim_node(struct mem_cgroup *mem,
> +                                     const nodemask_t *nodes);
>
>  static inline
>  int mm_match_cgroup(const struct mm_struct *mm, const struct mem_cgroup *cgroup)
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index c4e1904..e22351a 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -279,6 +279,11 @@ struct mem_cgroup {
>       u64 high_wmark_distance;
>       u64 low_wmark_distance;
>
> +     /* While doing per cgroup background reclaim, we cache the
> +      * last node we reclaimed from
> +      */
> +     int last_scanned_node;
> +
>       wait_queue_head_t *kswapd_wait;
>  };
>
> @@ -1536,6 +1541,32 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
>  }
>
>  /*
> + * Visit the first node after the last_scanned_node of @mem and use that to
> + * reclaim free pages from.
> + */
> +int
> +mem_cgroup_select_victim_node(struct mem_cgroup *mem, const nodemask_t *nodes)
> +{
> +     int next_nid;
> +     int last_scanned;
> +
> +     last_scanned = mem->last_scanned_node;
> +
> +     /* Initial stage and start from node0 */
> +     if (last_scanned == -1)
> +             next_nid = 0;
> +     else
> +             next_nid = next_node(last_scanned, *nodes);
> +

IIUC, mem->last_scanned_node should be initialized to MAX_NUMNODES.
Then, we can remove above check.

Thanks,
-Kame

> +     if (next_nid == MAX_NUMNODES)
> +             next_nid = first_node(*nodes);
> +
> +     mem->last_scanned_node = next_nid;
> +
> +     return next_nid;
> +}
> +
> +/*
>   * Check OOM-Killer is already running under our hierarchy.
>   * If someone is running, return false.
>   */
> @@ -4693,6 +4724,14 @@ wait_queue_head_t *mem_cgroup_kswapd_wait(struct mem_cgroup *mem)
>       return mem->kswapd_wait;
>  }
>
> +int mem_cgroup_last_scanned_node(struct mem_cgroup *mem)
> +{
> +     if (!mem)
> +             return -1;
> +
> +     return mem->last_scanned_node;
> +}
> +
>  static int mem_cgroup_soft_limit_tree_init(void)
>  {
>       struct mem_cgroup_tree_per_node *rtpn;
> @@ -4768,6 +4807,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
>               res_counter_init(&mem->memsw, NULL);
>       }
>       mem->last_scanned_child = 0;
> +     mem->last_scanned_node = -1;
>       INIT_LIST_HEAD(&mem->oom_notify);
>
>       if (parent)
> --
> 1.7.3.1
>

> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@kvack.org.  For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
>