Re: [PATCH 6/8] mm: vmscan: simplify memcg vs. global shrinker invocation

Michal Hocko
2015-10-23T13:26:27Z

On Thu 22-10-15 00:21:34, Johannes Weiner wrote:
> Letting shrink_slab() handle the root_mem_cgroup, and implicitely the
> !CONFIG_MEMCG case, allows shrink_zone() to invoke the shrinkers
> unconditionally from within the memcg iteration loop.
>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
> include/linux/memcontrol.h | 2 ++
> mm/vmscan.c | 31 ++++++++++++++++---------------
> 2 files changed, 18 insertions(+), 15 deletions(-)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 6f1e0f8..d66ae18 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -482,6 +482,8 @@ void mem_cgroup_split_huge_fixup(struct page *head);
> #else /* CONFIG_MEMCG */
> struct mem_cgroup;
>
> +#define root_mem_cgroup NULL
> +
> static inline void mem_cgroup_events(struct mem_cgroup *memcg,
> enum mem_cgroup_events_index idx,
> unsigned int nr)
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 9b52ecf..ecc2125 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -411,6 +411,10 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
> struct shrinker *shrinker;
> unsigned long freed = 0;
>
> + /* Global shrinker mode */
> + if (memcg == root_mem_cgroup)
> + memcg = NULL;
> +
> if (memcg && !memcg_kmem_is_active(memcg))
> return 0;
>
> @@ -2417,11 +2421,22 @@ static bool shrink_zone(struct zone *zone, struct scan_control *sc,
> shrink_lruvec(lruvec, swappiness, sc, &lru_pages);
> zone_lru_pages += lru_pages;
>
> - if (memcg && is_classzone)
> + /*
> + * Shrink the slab caches in the same proportion that
> + * the eligible LRU pages were scanned.
> + */
> + if (is_classzone) {
> shrink_slab(sc->gfp_mask, zone_to_nid(zone),
> memcg, sc->nr_scanned - scanned,
> lru_pages);
>
> + if (reclaim_state) {
> + sc->nr_reclaimed +=
> + reclaim_state->reclaimed_slab;
> + reclaim_state->reclaimed_slab = 0;
> + }
> + }
> +
> /*
> * Direct reclaim and kswapd have to scan all memory
> * cgroups to fulfill the overall scan target for the
> @@ -2439,20 +2454,6 @@ static bool shrink_zone(struct zone *zone, struct scan_control *sc,
> }
> } while ((memcg = mem_cgroup_iter(root, memcg, &reclaim)));
>
> - /*
> - * Shrink the slab caches in the same proportion that
> - * the eligible LRU pages were scanned.
> - */
> - if (global_reclaim(sc) && is_classzone)
> - shrink_slab(sc->gfp_mask, zone_to_nid(zone), NULL,
> - sc->nr_scanned - nr_scanned,
> - zone_lru_pages);
> -
> - if (reclaim_state) {
> - sc->nr_reclaimed += reclaim_state->reclaimed_slab;
> - reclaim_state->reclaimed_slab = 0;
> - }
> -
> vmpressure(sc->gfp_mask, sc->target_mem_cgroup,
> sc->nr_scanned - nr_scanned,
> sc->nr_reclaimed - nr_reclaimed);
> --
> 2.6.1

--
Michal Hocko
SUSE Labs