On Thu, Apr 14, 2011 at 5:40 PM, KAMEZAWA Hiroyuki <
kamezawa.hiroyu@jp.fujitsu.com> wrote:

> 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.
>

make sense. will make the change on next post.

--Ying

>
> 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
> >
> > --
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