Re: [PATCH v2 21/28] vmscan: also shrink slab in memcg pressure

[Sha Zhengju <handai.szj@gmail.com>]

Hi Glauber,

On Fri, Mar 29, 2013 at 5:14 PM, Glauber Costa <glommer@parallels.com> wrote:
> Without the surrounding infrastructure, this patch is a bit of a hammer:
> it will basically shrink objects from all memcgs under memcg pressure.
> At least, however, we will keep the scan limited to the shrinkers marked
> as per-memcg.
>
> Future patches will implement the in-shrinker logic to filter objects
> based on its memcg association.
>
> Signed-off-by: Glauber Costa <glommer@parallels.com>
> Cc: Dave Chinner <dchinner@redhat.com>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Rik van Riel <riel@redhat.com>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Michal Hocko <mhocko@suse.cz>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> ---
>  include/linux/memcontrol.h | 17 +++++++++++++++++
>  include/linux/shrinker.h   |  4 ++++
>  mm/memcontrol.c            | 16 +++++++++++++++-
>  mm/vmscan.c                | 46 +++++++++++++++++++++++++++++++++++++++++++---
>  4 files changed, 79 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index d6183f0..4c24249 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -199,6 +199,9 @@ void mem_cgroup_split_huge_fixup(struct page *head);
>  bool mem_cgroup_bad_page_check(struct page *page);
>  void mem_cgroup_print_bad_page(struct page *page);
>  #endif
> +
> +unsigned long
> +memcg_zone_reclaimable_pages(struct mem_cgroup *memcg, struct zone *zone);
>  #else /* CONFIG_MEMCG */
>  struct mem_cgroup;
>
> @@ -377,6 +380,12 @@ static inline void mem_cgroup_replace_page_cache(struct page *oldpage,
>                                 struct page *newpage)
>  {
>  }
> +
> +static inline unsigned long
> +memcg_zone_reclaimable_pages(struct mem_cgroup *memcg, struct zone *zone)
> +{
> +       return 0;
> +}
>  #endif /* CONFIG_MEMCG */
>
>  #if !defined(CONFIG_MEMCG) || !defined(CONFIG_DEBUG_VM)
> @@ -429,6 +438,8 @@ static inline bool memcg_kmem_enabled(void)
>         return static_key_false(&memcg_kmem_enabled_key);
>  }
>
> +bool memcg_kmem_is_active(struct mem_cgroup *memcg);
> +
>  /*
>   * In general, we'll do everything in our power to not incur in any overhead
>   * for non-memcg users for the kmem functions. Not even a function call, if we
> @@ -562,6 +573,12 @@ memcg_kmem_get_cache(struct kmem_cache *cachep, gfp_t gfp)
>         return __memcg_kmem_get_cache(cachep, gfp);
>  }
>  #else
> +
> +static inline bool memcg_kmem_is_active(struct mem_cgroup *memcg)
> +{
> +       return false;
> +}
> +
>  #define for_each_memcg_cache_index(_idx)       \
>         for (; NULL; )
>
> diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
> index d4636a0..4e9e53b 100644
> --- a/include/linux/shrinker.h
> +++ b/include/linux/shrinker.h
> @@ -20,6 +20,9 @@ struct shrink_control {
>
>         /* shrink from these nodes */
>         nodemask_t nodes_to_scan;
> +
> +       /* reclaim from this memcg only (if not NULL) */
> +       struct mem_cgroup *target_mem_cgroup;
>  };
>
>  /*
> @@ -45,6 +48,7 @@ struct shrinker {
>
>         int seeks;      /* seeks to recreate an obj */
>         long batch;     /* reclaim batch size, 0 = default */
> +       bool memcg_shrinker; /* memcg-aware shrinker */
>
>         /* These are for internal use */
>         struct list_head list;
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 2b55222..ecdae39 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -386,7 +386,7 @@ static inline void memcg_kmem_set_active(struct mem_cgroup *memcg)
>         set_bit(KMEM_ACCOUNTED_ACTIVE, &memcg->kmem_account_flags);
>  }
>
> -static bool memcg_kmem_is_active(struct mem_cgroup *memcg)
> +bool memcg_kmem_is_active(struct mem_cgroup *memcg)
>  {
>         return test_bit(KMEM_ACCOUNTED_ACTIVE, &memcg->kmem_account_flags);
>  }
> @@ -942,6 +942,20 @@ mem_cgroup_zone_nr_lru_pages(struct mem_cgroup *memcg, int nid, int zid,
>         return ret;
>  }
>
> +unsigned long
> +memcg_zone_reclaimable_pages(struct mem_cgroup *memcg, struct zone *zone)
> +{
> +       int nid = zone_to_nid(zone);
> +       int zid = zone_idx(zone);
> +       unsigned long val;
> +
> +       val = mem_cgroup_zone_nr_lru_pages(memcg, nid, zid, LRU_ALL_FILE);
> +       if (do_swap_account)

IMHO May get_nr_swap_pages() be more appropriate here?

> +               val += mem_cgroup_zone_nr_lru_pages(memcg, nid, zid,
> +                                                   LRU_ALL_ANON);
> +       return val;
> +}
> +
>  static unsigned long
>  mem_cgroup_node_nr_lru_pages(struct mem_cgroup *memcg,
>                         int nid, unsigned int lru_mask)
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 232dfcb..43928fd 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -138,11 +138,42 @@ static bool global_reclaim(struct scan_control *sc)
>  {
>         return !sc->target_mem_cgroup;
>  }
> +
> +/*
> + * kmem reclaim should usually not be triggered when we are doing targetted
> + * reclaim. It is only valid when global reclaim is triggered, or when the
> + * underlying memcg has kmem objects.
> + */
> +static bool has_kmem_reclaim(struct scan_control *sc)
> +{
> +       return !sc->target_mem_cgroup ||
> +               memcg_kmem_is_active(sc->target_mem_cgroup);
> +}
> +
> +static unsigned long
> +zone_nr_reclaimable_pages(struct scan_control *sc, struct zone *zone)
> +{
> +       if (global_reclaim(sc))
> +               return zone_reclaimable_pages(zone);
> +       return memcg_zone_reclaimable_pages(sc->target_mem_cgroup, zone);
> +}
> +
>  #else
>  static bool global_reclaim(struct scan_control *sc)
>  {
>         return true;
>  }
> +
> +static bool has_kmem_reclaim(struct scan_control *sc)
> +{
> +       return true;
> +}
> +
> +static unsigned long
> +zone_nr_reclaimable_pages(struct scan_control *sc, struct zone *zone)
> +{
> +       return zone_reclaimable_pages(zone);
> +}
>  #endif
>
>  static unsigned long get_lru_size(struct lruvec *lruvec, enum lru_list lru)
> @@ -221,6 +252,14 @@ unsigned long shrink_slab(struct shrink_control *sc,
>                 long batch_size = shrinker->batch ? shrinker->batch
>                                                   : SHRINK_BATCH;
>
> +               /*
> +                * If we don't have a target mem cgroup, we scan them all.
> +                * Otherwise we will limit our scan to shrinkers marked as
> +                * memcg aware
> +                */
> +               if (sc->target_mem_cgroup && !shrinker->memcg_shrinker)
> +                       continue;
> +
>                 max_pass = shrinker->count_objects(shrinker, sc);
>                 WARN_ON(max_pass < 0);
>                 if (max_pass <= 0)
> @@ -2163,9 +2202,9 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
>
>                 /*
>                  * Don't shrink slabs when reclaiming memory from
> -                * over limit cgroups
> +                * over limit cgroups, unless we know they have kmem objects
>                  */
> -               if (global_reclaim(sc)) {
> +               if (has_kmem_reclaim(sc)) {
>                         unsigned long lru_pages = 0;
>
>                         nodes_clear(shrink->nodes_to_scan);
> @@ -2174,7 +2213,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
>                                 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
>                                         continue;
>
> -                               lru_pages += zone_reclaimable_pages(zone);
> +                               lru_pages += zone_nr_reclaimable_pages(sc, zone);
>                                 node_set(zone_to_nid(zone),
>                                          shrink->nodes_to_scan);
>                         }
> @@ -2443,6 +2482,7 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
>         };
>         struct shrink_control shrink = {
>                 .gfp_mask = sc.gfp_mask,
> +               .target_mem_cgroup = memcg,
>         };
>
>         /*
> --
> 1.8.1.4
>
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> Containers@lists.linux-foundation.org
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--
Thanks,
Sha

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