This patch makes direct reclaim path shrink slabs not only on global
memory pressure, but also when we reach memory cgroup limit. To achieve
that, it introduces a new per-shrinker flag, SHRINKER_MEMCG_AWARE, which
should be set if the shrinker can handle per-memcg reclaim. For such
shrinkers, shrink_slab() will iterate over all eligible memory cgroups
(i.e. the cgroup that triggered the reclaim and all its descendants) and
pass the current memory cgroup to the shrinker in shrink_control.memcg
just like it passes the current NUMA node to NUMA-aware shrinkers. It
is completely up to memcg-aware shrinkers how to organize objects in
order to provide required functionality. Currently none of the existing
shrinkers is memcg-aware, but next patches will introduce per-memcg
list_lru, which will facilitate the process of turning shrinkers that
use list_lru to be memcg-aware.
The number of slab objects scanned on memcg pressure is calculated in
the same way as on global pressure - it is proportional to the number of
pages scanned over the number of pages eligible for reclaim (i.e. the
number of on-LRU pages in the target memcg and all its descendants) -
except we do not employ the nr_deferred per-shrinker counter to avoid
memory cgroup isolation issues. Ideally, this counter should be made
per-memcg.
Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Cc: Dave Chinner <dchinner@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Balbir Singh <bsingharora@xxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
---
include/linux/memcontrol.h | 22 +++++++++
include/linux/shrinker.h | 10 +++-
mm/memcontrol.c | 37 +++++++++++++-
mm/vmscan.c | 117 +++++++++++++++++++++++++++++++-------------
4 files changed, 150 insertions(+), 36 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index b3e7a66..c0f24a9 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -80,6 +80,9 @@ extern int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
struct lruvec *mem_cgroup_zone_lruvec(struct zone *, struct mem_cgroup *);
struct lruvec *mem_cgroup_page_lruvec(struct page *, struct zone *);
+unsigned long mem_cgroup_zone_reclaimable_pages(struct zone *,
+ struct mem_cgroup *);
+
/* For coalescing uncharge for reducing memcg' overhead*/
extern void mem_cgroup_uncharge_start(void);
extern void mem_cgroup_uncharge_end(void);
@@ -289,6 +292,12 @@ static inline struct lruvec *mem_cgroup_page_lruvec(struct page *page,
return &zone->lruvec;
}
+static inline unsigned long mem_cgroup_zone_reclaimable_pages(struct zone *zone,
+ struct mem_cgroup *)
+{
+ return 0;
+}
+
static inline struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
{
return NULL;
@@ -479,6 +488,9 @@ static inline bool memcg_kmem_enabled(void)
return static_key_false(&memcg_kmem_enabled_key);
}
+bool memcg_kmem_is_active(struct mem_cgroup *memcg);
+bool memcg_kmem_should_reclaim(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
@@ -620,6 +632,16 @@ static inline bool memcg_kmem_enabled(void)
return false;
}
+static inline bool memcg_kmem_is_active(struct mem_cgroup *memcg)
+{
+ return false;
+}
+
+static inline bool memcg_kmem_should_reclaim(struct mem_cgroup *memcg)
+{
+ return false;
+}
+
static inline bool
memcg_kmem_newpage_charge(gfp_t gfp, struct mem_cgroup **memcg, int order)
{
diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
index 68c0970..ab79b17 100644
--- a/include/linux/shrinker.h
+++ b/include/linux/shrinker.h
@@ -20,8 +20,15 @@ struct shrink_control {
/* shrink from these nodes */
nodemask_t nodes_to_scan;
+
+ /* shrink from this memory cgroup hierarchy (if not NULL) */
+ struct mem_cgroup *target_mem_cgroup;
+
/* current node being shrunk (for NUMA aware shrinkers) */
int nid;
+
+ /* current memcg being shrunk (for memcg aware shrinkers) */
+ struct mem_cgroup *memcg;
};
#define SHRINK_STOP (~0UL)
@@ -63,7 +70,8 @@ struct shrinker {
#define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
/* Flags */
-#define SHRINKER_NUMA_AWARE (1 << 0)
+#define SHRINKER_NUMA_AWARE (1 << 0)
+#define SHRINKER_MEMCG_AWARE (1 << 1)
extern int register_shrinker(struct shrinker *);
extern void unregister_shrinker(struct shrinker *);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 3a92ab3..3f12cec 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -358,7 +358,7 @@ 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);
}
@@ -1333,6 +1333,26 @@ out:
return lruvec;
}
+unsigned long mem_cgroup_zone_reclaimable_pages(struct zone *zone,
+ struct mem_cgroup *memcg)
+{
+ int nid = zone_to_nid(zone);
+ int zid = zone_idx(zone);
+ unsigned long nr = 0;
+ struct mem_cgroup *iter;
+
+ iter = memcg;
+ do {
+ nr += mem_cgroup_zone_nr_lru_pages(iter, nid, zid,
+ LRU_ALL_FILE);
+ if (do_swap_account)
+ nr += mem_cgroup_zone_nr_lru_pages(iter, nid, zid,
+ LRU_ALL_ANON);
+ iter = mem_cgroup_iter(memcg, iter, NULL);
+ } while (iter);
+ return nr;
+}
+
/*
* Following LRU functions are allowed to be used without PCG_LOCK.
* Operations are called by routine of global LRU independently from memcg.
@@ -2959,6 +2979,21 @@ static inline bool memcg_can_account_kmem(struct mem_cgroup *memcg)
(memcg->kmem_account_flags & KMEM_ACCOUNTED_MASK);
}
+bool memcg_kmem_should_reclaim(struct mem_cgroup *memcg)
+{
+ struct mem_cgroup *iter;
+
+ iter = memcg;
+ do {
+ if (memcg_kmem_is_active(iter)) {
+ mem_cgroup_iter_break(memcg, iter);
+ return true;
+ }
+ iter = mem_cgroup_iter(memcg, iter, NULL);
+ } while (iter);
+ return false;
+}
+
/*
* helper for acessing a memcg's index. It will be used as an index in the
* child cache array in kmem_cache, and also to derive its name. This function
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 7601b95..04df967 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -225,7 +225,7 @@ shrink_slab_node(struct shrink_control *shrinkctl, struct shrinker *shrinker,
unsigned long long delta;
long total_scan;
long max_pass;
- long nr;
+ long nr = 0;
long new_nr;
int nid = shrinkctl->nid;
long batch_size = shrinker->batch ? shrinker->batch
@@ -236,11 +236,17 @@ shrink_slab_node(struct shrink_control *shrinkctl, struct shrinker *shrinker,
return 0;
/*
- * copy the current shrinker scan count into a local variable
- * and zero it so that other concurrent shrinker invocations
- * don't also do this scanning work.
+ * Do not touch global counter of deferred objects on memcg pressure to
+ * avoid isolation issues. Ideally the counter should be per-memcg.
*/
- nr = atomic_long_xchg(&shrinker->nr_deferred[nid], 0);
+ if (!shrinkctl->target_mem_cgroup) {
+ /*
+ * copy the current shrinker scan count into a local variable
+ * and zero it so that other concurrent shrinker invocations
+ * don't also do this scanning work.
+ */
+ nr = atomic_long_xchg(&shrinker->nr_deferred[nid], 0);
+ }
total_scan = nr;
delta = (4 * fraction) / shrinker->seeks;
@@ -296,21 +302,46 @@ shrink_slab_node(struct shrink_control *shrinkctl, struct shrinker *shrinker,
cond_resched();
}
- /*
- * move the unused scan count back into the shrinker in a
- * manner that handles concurrent updates. If we exhausted the
- * scan, there is no need to do an update.
- */
- if (total_scan > 0)
- new_nr = atomic_long_add_return(total_scan,
+ if (!shrinkctl->target_mem_cgroup) {
+ /*
+ * move the unused scan count back into the shrinker in a
+ * manner that handles concurrent updates. If we exhausted the
+ * scan, there is no need to do an update.
+ */
+ if (total_scan > 0)
+ new_nr = atomic_long_add_return(total_scan,
&shrinker->nr_deferred[nid]);
- else
- new_nr = atomic_long_read(&shrinker->nr_deferred[nid]);
+ else
+ new_nr = atomic_long_read(&shrinker->nr_deferred[nid]);
+ }
trace_mm_shrink_slab_end(shrinker, freed, nr, new_nr);
return freed;
}
+static unsigned long
+shrink_slab_memcg(struct shrink_control *shrinkctl, struct shrinker *shrinker,
+ unsigned long fraction, unsigned long denominator)
+{
+ unsigned long freed = 0;
+
+ if (shrinkctl->memcg && !memcg_kmem_is_active(shrinkctl->memcg))
+ return 0;
+
+ for_each_node_mask(shrinkctl->nid, shrinkctl->nodes_to_scan) {
+ if (!node_online(shrinkctl->nid))
+ continue;
+
+ if (!(shrinker->flags & SHRINKER_NUMA_AWARE) &&
+ (shrinkctl->nid != 0))
+ break;
+
+ freed += shrink_slab_node(shrinkctl, shrinker,
+ fraction, denominator);
+ }
+ return freed;
+}
+
/*
* Call the shrink functions to age shrinkable caches
*
@@ -352,18 +383,23 @@ unsigned long shrink_slab(struct shrink_control *shrinkctl,
}
list_for_each_entry(shrinker, &shrinker_list, list) {
- for_each_node_mask(shrinkctl->nid, shrinkctl->nodes_to_scan) {
- if (!node_online(shrinkctl->nid))
- continue;
-
- if (!(shrinker->flags & SHRINKER_NUMA_AWARE) &&
- (shrinkctl->nid != 0))
+ shrinkctl->memcg = shrinkctl->target_mem_cgroup;
+ do {
+ if (!(shrinker->flags & SHRINKER_MEMCG_AWARE) &&
+ (shrinkctl->memcg != NULL)) {
+ mem_cgroup_iter_break(
+ shrinkctl->target_mem_cgroup,
+ shrinkctl->memcg);
break;
+ }
- freed += shrink_slab_node(shrinkctl, shrinker,
- fraction, denominator);
+ freed += shrink_slab_memcg(shrinkctl, shrinker,
+ fraction, denominator);
- }
+ shrinkctl->memcg = mem_cgroup_iter(
+ shrinkctl->target_mem_cgroup,
+ shrinkctl->memcg, NULL);
+ } while (shrinkctl->memcg);
}
up_read(&shrinker_rwsem);
out:
@@ -2285,6 +2321,7 @@ static bool shrink_zones(struct zonelist *zonelist,
struct reclaim_state *reclaim_state = current->reclaim_state;
struct shrink_control shrink = {
.gfp_mask = sc->gfp_mask,
+ .target_mem_cgroup = sc->target_mem_cgroup,
};
/*
@@ -2301,17 +2338,22 @@ static bool shrink_zones(struct zonelist *zonelist,
gfp_zone(sc->gfp_mask), sc->nodemask) {
if (!populated_zone(zone))
continue;
+
+ if (global_reclaim(sc) &&
+ !cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
+ continue;
+
+ lru_pages += global_reclaim(sc) ?
+ zone_reclaimable_pages(zone) :
+ mem_cgroup_zone_reclaimable_pages(zone,
+ sc->target_mem_cgroup);
+ node_set(zone_to_nid(zone), shrink.nodes_to_scan);
+
/*
* Take care memory controller reclaiming has small influence
* to global LRU.
*/
if (global_reclaim(sc)) {
- if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
- continue;
-
- lru_pages += zone_reclaimable_pages(zone);
- node_set(zone_to_nid(zone), shrink.nodes_to_scan);
-
if (sc->priority != DEF_PRIORITY &&
!zone_reclaimable(zone))
continue; /* Let kswapd poll it */
@@ -2349,12 +2391,11 @@ static bool shrink_zones(struct zonelist *zonelist,
}
/*
- * Don't shrink slabs when reclaiming memory from over limit
- * cgroups but do shrink slab at least once when aborting
- * reclaim for compaction to avoid unevenly scanning file/anon
- * LRU pages over slab pages.
+ * Shrink slabs at least once when aborting reclaim for compaction
+ * to avoid unevenly scanning file/anon LRU pages over slab pages.
*/
- if (global_reclaim(sc)) {
+ if (global_reclaim(sc) ||
+ memcg_kmem_should_reclaim(sc->target_mem_cgroup)) {
shrink_slab(&shrink, sc->nr_scanned, lru_pages);
if (reclaim_state) {
sc->nr_reclaimed += reclaim_state->reclaimed_slab;
@@ -2648,6 +2689,7 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
struct zonelist *zonelist;
unsigned long nr_reclaimed;
int nid;
+ struct reclaim_state reclaim_state;
struct scan_control sc = {
.may_writepage = !laptop_mode,
.may_unmap = 1,
@@ -2670,6 +2712,10 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
zonelist = NODE_DATA(nid)->node_zonelists;
+ lockdep_set_current_reclaim_state(sc.gfp_mask);
+ reclaim_state.reclaimed_slab = 0;
+ current->reclaim_state = &reclaim_state;
+
trace_mm_vmscan_memcg_reclaim_begin(0,
sc.may_writepage,
sc.gfp_mask);
@@ -2678,6 +2724,9 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
+ current->reclaim_state = NULL;
+ lockdep_clear_current_reclaim_state();
+
return nr_reclaimed;
}
#endif
--
1.7.10.4
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