[PATCH v6 21/31] vmscan: also shrink slab in memcg pressure

Glauber Costa
2013-05-12T18:13:42Z

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@openvz.org>
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 7b4d9d7..489c6d7 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -200,6 +200,9 @@ 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;

@@ -378,6 +381,12 @@ 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)
@@ -430,6 +439,8 @@ 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
@@ -563,6 +574,12 @@ 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 00a3e57..3b08869 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 e34da3c..980bd2d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -465,7 +465,7 @@ 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);
}
@@ -1044,6 +1044,20 @@ 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)
+ 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 64f66f6..eb5e67c 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -139,11 +139,42 @@ 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)
@@ -222,6 +253,14 @@ unsigned long shrink_slab(struct shrink_control *shrinkctl,
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 (shrinkctl->target_mem_cgroup && !shrinker->memcg_shrinker)
+ continue;
+
max_pass = shrinker->count_objects(shrinker, shrinkctl);
WARN_ON(max_pass < 0);
if (max_pass <= 0)
@@ -2172,9 +2211,9 @@ 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);
@@ -2183,7 +2222,7 @@ 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);
}
@@ -2452,6 +2491,7 @@ 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