[PATCH v11 00/15] kmemcg shrinkers

[PATCH v11 00/15] kmemcg shrinkers

[Vladimir Davydov]

This patchset implements targeted shrinking for memcg when kmem limits are
present. So far, we've been accounting kernel objects but failing allocations
when short of memory. This is because our only option would be to call the
global shrinker, depleting objects from all caches and breaking isolation.

The main idea is to associate per-memcg lists with each of the LRUs. The main
LRU still provides a single entry point and when adding or removing an element
from the LRU, we use the page information to figure out which memcg it belongs
to and relay it to the right list.

The bulk of the code is written by Glauber Costa. The only change I introduced
myself in this iteration is reworking per-memcg LRU lists. Instead of extending
the existing list_lru structure, which seems to be neat as is, I introduced a
new one, memcg_list_lru, which aggregates list_lru objects for each kmem-active
memcg and keeps them uptodate as memcgs are created/destroyed. I hope this
simplified call paths and made the code easier to read.

The patchset is based on top of Linux 3.12-rc6.

Any comments and proposals are appreciated.

== Known issues ==

 * In case kmem limit is less than sum mem limit, reaching memcg kmem limit
   will result in an attempt to shrink all memcg slabs (see
   try_to_free_mem_cgroup_kmem()). Although this is better than simply failing
   allocation as it works now, it is still to be improved.

 * Since FS shrinkers can't be executed on __GFP_FS allocations, such
   allocations will fail if memcg kmem limit is less than sum mem limit and the
   memcg kmem usage is close to its limit. Glauber proposed to schedule a
   worker which would shrink kmem in the background on such allocations.
   However, this approach does not eliminate failures completely, it just makes
   them rarer. I'm thinking on implementing soft limits for memcg kmem so that
   striking the soft limit will trigger the reclaimer, but won't fail the
   allocation. I would appreciate any other proposals on how this can be fixed.

 * Only dcache and icache are reclaimed on memcg pressure. Other FS objects are
   left for global pressure only. However, it should not be a serious problem
   to make them reclaimable too by passing on memcg to the FS-layer and letting
   each FS decide if its internal objects are shrinkable on memcg pressure.

== Changes from v10 ==

 * Rework per-memcg list_lru infrastructure.

Previous iteration (with full changelog) can be found here:

http://www.spinics.net/lists/linux-fsdevel/msg66632.html

Glauber Costa (12):
  memcg: make cache index determination more robust
  memcg: consolidate callers of memcg_cache_id
  vmscan: also shrink slab in memcg pressure
  memcg: move initialization to memcg creation
  memcg: move stop and resume accounting functions
  memcg: per-memcg kmem shrinking
  memcg: scan cache objects hierarchically
  vmscan: take at least one pass with shrinkers
  memcg: allow kmem limit to be resized down
  vmpressure: in-kernel notifications
  memcg: reap dead memcgs upon global memory pressure
  memcg: flush memcg items upon memcg destruction

Vladimir Davydov (3):
  memcg,list_lru: add per-memcg LRU list infrastructure
  memcg,list_lru: add function walking over all lists of a per-memcg
    LRU
  super: make icache, dcache shrinkers memcg-aware

 fs/dcache.c                |   25 +-
 fs/inode.c                 |   16 +-
 fs/internal.h              |    9 +-
 fs/super.c                 |   47 +--
 include/linux/fs.h         |    4 +-
 include/linux/list_lru.h   |   77 +++++
 include/linux/memcontrol.h |   23 ++
 include/linux/shrinker.h   |    6 +-
 include/linux/swap.h       |    2 +
 include/linux/vmpressure.h |    5 +
 mm/memcontrol.c            |  704 +++++++++++++++++++++++++++++++++++++++-----
 mm/vmpressure.c            |   53 +++-
 mm/vmscan.c                |  178 +++++++++--
 13 files changed, 1014 insertions(+), 135 deletions(-)

-- 
1.7.10.4

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[PATCH v11 01/15] memcg: make cache index determination more robust

[Vladimir Davydov]

From: Glauber Costa <glommer@openvz.org>

I caught myself doing something like the following outside memcg core:

	memcg_id = -1;
	if (memcg && memcg_kmem_is_active(memcg))
		memcg_id = memcg_cache_id(memcg);

to be able to handle all possible memcgs in a sane manner. In particular, the
root cache will have kmemcg_id = -1 (just because we don't call memcg_kmem_init
to the root cache since it is not limitable). We have always coped with that by
making sure we sanitize which cache is passed to memcg_cache_id. Although this
example is given for root, what we really need to know is whether or not a
cache is kmem active.

But outside the memcg core testing for root, for instance, is not trivial since
we don't export mem_cgroup_is_root. I ended up realizing that this tests really
belong inside memcg_cache_id. This patch moves a similar but stronger test
inside memcg_cache_id and make sure it always return a meaningful value.

Signed-off-by: Glauber Costa <glommer@openvz.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 mm/memcontrol.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 34d3ca9..0712277 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3057,7 +3057,9 @@ void memcg_cache_list_add(struct mem_cgroup *memcg, struct kmem_cache *cachep)
  */
 int memcg_cache_id(struct mem_cgroup *memcg)
 {
-	return memcg ? memcg->kmemcg_id : -1;
+	if (!memcg || !memcg_can_account_kmem(memcg))
+		return -1;
+	return memcg->kmemcg_id;
 }
 
 /*
-- 
1.7.10.4

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[PATCH v11 02/15] memcg: consolidate callers of memcg_cache_id

[Vladimir Davydov]

From: Glauber Costa <glommer@openvz.org>

Each caller of memcg_cache_id ends up sanitizing its parameters in its own way.
Now that the memcg_cache_id itself is more robust, we can consolidate this.

Also, as suggested by Michal, a special helper memcg_cache_idx is used when the
result is expected to be used directly as an array index to make sure we never
accesses in a negative index.

Signed-off-by: Glauber Costa <glommer@openvz.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 mm/memcontrol.c |   49 +++++++++++++++++++++++++++++--------------------
 1 file changed, 29 insertions(+), 20 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0712277..0a5cc30 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2937,6 +2937,30 @@ static inline bool memcg_can_account_kmem(struct mem_cgroup *memcg)
 }
 
 /*
+ * 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
+ * will return -1 when this is not a kmem-limited memcg.
+ */
+int memcg_cache_id(struct mem_cgroup *memcg)
+{
+	if (!memcg || !memcg_can_account_kmem(memcg))
+		return -1;
+	return memcg->kmemcg_id;
+}
+
+/*
+ * This helper around memcg_cache_id is not intented for use outside memcg
+ * core. It is meant for places where the cache id is used directly as an array
+ * index
+ */
+static int memcg_cache_idx(struct mem_cgroup *memcg)
+{
+	int ret = memcg_cache_id(memcg);
+	BUG_ON(ret < 0);
+	return ret;
+}
+
+/*
  * This is a bit cumbersome, but it is rarely used and avoids a backpointer
  * in the memcg_cache_params struct.
  */
@@ -2946,7 +2970,7 @@ static struct kmem_cache *memcg_params_to_cache(struct memcg_cache_params *p)
 
 	VM_BUG_ON(p->is_root_cache);
 	cachep = p->root_cache;
-	return cachep->memcg_params->memcg_caches[memcg_cache_id(p->memcg)];
+	return cachep->memcg_params->memcg_caches[memcg_cache_idx(p->memcg)];
 }
 
 #ifdef CONFIG_SLABINFO
@@ -3051,18 +3075,6 @@ void memcg_cache_list_add(struct mem_cgroup *memcg, struct kmem_cache *cachep)
 }
 
 /*
- * 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
- * will return -1 when this is not a kmem-limited memcg.
- */
-int memcg_cache_id(struct mem_cgroup *memcg)
-{
-	if (!memcg || !memcg_can_account_kmem(memcg))
-		return -1;
-	return memcg->kmemcg_id;
-}
-
-/*
  * This ends up being protected by the set_limit mutex, during normal
  * operation, because that is its main call site.
  *
@@ -3224,7 +3236,7 @@ void memcg_release_cache(struct kmem_cache *s)
 		goto out;
 
 	memcg = s->memcg_params->memcg;
-	id  = memcg_cache_id(memcg);
+	id = memcg_cache_idx(memcg);
 
 	root = s->memcg_params->root_cache;
 	root->memcg_params->memcg_caches[id] = NULL;
@@ -3387,9 +3399,7 @@ static struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg,
 	struct kmem_cache *new_cachep;
 	int idx;
 
-	BUG_ON(!memcg_can_account_kmem(memcg));
-
-	idx = memcg_cache_id(memcg);
+	idx = memcg_cache_idx(memcg);
 
 	mutex_lock(&memcg_cache_mutex);
 	new_cachep = cachep->memcg_params->memcg_caches[idx];
@@ -3562,10 +3572,9 @@ struct kmem_cache *__memcg_kmem_get_cache(struct kmem_cache *cachep,
 	rcu_read_lock();
 	memcg = mem_cgroup_from_task(rcu_dereference(current->mm->owner));
 
-	if (!memcg_can_account_kmem(memcg))
-		goto out;
-
 	idx = memcg_cache_id(memcg);
+	if (idx < 0)
+		return cachep;
 
 	/*
 	 * barrier to mare sure we're always seeing the up to date value.  The
-- 
1.7.10.4

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[PATCH v11 03/15] vmscan: also shrink slab in memcg pressure

[Vladimir Davydov]

From: Glauber Costa <glommer@openvz.org>

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   |    6 +++++-
 mm/memcontrol.c            |   16 +++++++++++++-
 mm/vmscan.c                |   50 +++++++++++++++++++++++++++++++++++++++-----
 4 files changed, 82 insertions(+), 7 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index b3e7a66..d16ba51 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -231,6 +231,9 @@ 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;
 
@@ -427,6 +430,12 @@ 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)
@@ -479,6 +488,8 @@ 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
@@ -612,6 +623,12 @@ 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 68c0970..7d462b1 100644
--- a/include/linux/shrinker.h
+++ b/include/linux/shrinker.h
@@ -22,6 +22,9 @@ struct shrink_control {
 	nodemask_t nodes_to_scan;
 	/* current node being shrunk (for NUMA aware shrinkers) */
 	int nid;
+
+	/* reclaim from this memcg only (if not NULL) */
+	struct mem_cgroup *target_mem_cgroup;
 };
 
 #define SHRINK_STOP (~0UL)
@@ -63,7 +66,8 @@ 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 0a5cc30..41c216a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -356,7 +356,7 @@ 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);
 }
@@ -938,6 +938,20 @@ 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 eea668d..652dfa3 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -140,11 +140,41 @@ 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
 
 unsigned long zone_reclaimable_pages(struct zone *zone)
@@ -352,6 +382,15 @@ unsigned long shrink_slab(struct shrink_control *shrinkctl,
 	}
 
 	list_for_each_entry(shrinker, &shrinker_list, list) {
+		/*
+		 * 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->flags & SHRINKER_MEMCG_AWARE))
+			continue;
+
 		for_each_node_mask(shrinkctl->nid, shrinkctl->nodes_to_scan) {
 			if (!node_online(shrinkctl->nid))
 				continue;
@@ -2399,11 +2438,11 @@ static unsigned long do_try_to_free_pages(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.
+		 * cgroups unless we know they have kmem objects. But do shrink
+		 * slab at least once when aborting reclaim for compaction to
+		 * avoid unevenly scanning file/anon LRU pages over slab pages.
 		 */
-		if (global_reclaim(sc)) {
+		if (has_kmem_reclaim(sc)) {
 			unsigned long lru_pages = 0;
 
 			nodes_clear(shrink->nodes_to_scan);
@@ -2412,7 +2451,7 @@ 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);
 			}
@@ -2669,6 +2708,7 @@ 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,
 	};
 
 	/*
-- 
1.7.10.4

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[PATCH v11 04/15] memcg: move initialization to memcg creation

[Vladimir Davydov]

From: Glauber Costa <glommer@openvz.org>

Those structures are only used for memcgs that are effectively using
kmemcg. However, in a later patch I intend to use scan that list
inconditionally (list empty meaning no kmem caches present), which
simplifies the code a lot.

So move the initialization to early kmem creation.

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>
---
 mm/memcontrol.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 41c216a..5104d1f 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3120,8 +3120,6 @@ int memcg_update_cache_sizes(struct mem_cgroup *memcg)
 	}
 
 	memcg->kmemcg_id = num;
-	INIT_LIST_HEAD(&memcg->memcg_slab_caches);
-	mutex_init(&memcg->slab_caches_mutex);
 	return 0;
 }
 
@@ -5916,6 +5914,8 @@ static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
 {
 	int ret;
 
+	INIT_LIST_HEAD(&memcg->memcg_slab_caches);
+	mutex_init(&memcg->slab_caches_mutex);
 	memcg->kmemcg_id = -1;
 	ret = memcg_propagate_kmem(memcg);
 	if (ret)
-- 
1.7.10.4

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[PATCH v11 05/15] memcg: move stop and resume accounting functions

[Vladimir Davydov]

From: Glauber Costa <glommer@openvz.org>

I need to move this up a bit, and I am doing it in a separate patch just to
reduce churn in the patch that needs it.

Signed-off-by: Glauber Costa <glommer@openvz.org>
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>
---
 mm/memcontrol.c |   62 +++++++++++++++++++++++++++----------------------------
 1 file changed, 31 insertions(+), 31 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 5104d1f..bb38596 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2987,6 +2987,37 @@ static struct kmem_cache *memcg_params_to_cache(struct memcg_cache_params *p)
 	return cachep->memcg_params->memcg_caches[memcg_cache_idx(p->memcg)];
 }
 
+/*
+ * During the creation a new cache, we need to disable our accounting mechanism
+ * altogether. This is true even if we are not creating, but rather just
+ * enqueing new caches to be created.
+ *
+ * This is because that process will trigger allocations; some visible, like
+ * explicit kmallocs to auxiliary data structures, name strings and internal
+ * cache structures; some well concealed, like INIT_WORK() that can allocate
+ * objects during debug.
+ *
+ * If any allocation happens during memcg_kmem_get_cache, we will recurse back
+ * to it. This may not be a bounded recursion: since the first cache creation
+ * failed to complete (waiting on the allocation), we'll just try to create the
+ * cache again, failing at the same point.
+ *
+ * memcg_kmem_get_cache is prepared to abort after seeing a positive count of
+ * memcg_kmem_skip_account. So we enclose anything that might allocate memory
+ * inside the following two functions.
+ */
+static inline void memcg_stop_kmem_account(void)
+{
+	VM_BUG_ON(!current->mm);
+	current->memcg_kmem_skip_account++;
+}
+
+static inline void memcg_resume_kmem_account(void)
+{
+	VM_BUG_ON(!current->mm);
+	current->memcg_kmem_skip_account--;
+}
+
 #ifdef CONFIG_SLABINFO
 static int mem_cgroup_slabinfo_read(struct cgroup_subsys_state *css,
 				    struct cftype *cft, struct seq_file *m)
@@ -3262,37 +3293,6 @@ out:
 	kfree(s->memcg_params);
 }
 
-/*
- * During the creation a new cache, we need to disable our accounting mechanism
- * altogether. This is true even if we are not creating, but rather just
- * enqueing new caches to be created.
- *
- * This is because that process will trigger allocations; some visible, like
- * explicit kmallocs to auxiliary data structures, name strings and internal
- * cache structures; some well concealed, like INIT_WORK() that can allocate
- * objects during debug.
- *
- * If any allocation happens during memcg_kmem_get_cache, we will recurse back
- * to it. This may not be a bounded recursion: since the first cache creation
- * failed to complete (waiting on the allocation), we'll just try to create the
- * cache again, failing at the same point.
- *
- * memcg_kmem_get_cache is prepared to abort after seeing a positive count of
- * memcg_kmem_skip_account. So we enclose anything that might allocate memory
- * inside the following two functions.
- */
-static inline void memcg_stop_kmem_account(void)
-{
-	VM_BUG_ON(!current->mm);
-	current->memcg_kmem_skip_account++;
-}
-
-static inline void memcg_resume_kmem_account(void)
-{
-	VM_BUG_ON(!current->mm);
-	current->memcg_kmem_skip_account--;
-}
-
 static void kmem_cache_destroy_work_func(struct work_struct *w)
 {
 	struct kmem_cache *cachep;
-- 
1.7.10.4

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[PATCH v11 06/15] memcg: per-memcg kmem shrinking

[Vladimir Davydov]

From: Glauber Costa <glommer@openvz.org>

If the kernel limit is smaller than the user limit, we will have
situations in which our allocations fail but freeing user pages will buy
us nothing.  In those, we would like to call a specialized memcg
reclaimer that only frees kernel memory and leave the user memory alone.
Those are also expected to fail when we account memcg->kmem, instead of
when we account memcg->res. Based on that, this patch implements a
memcg-specific reclaimer, that only shrinks kernel objects, withouth
touching user pages.

There might be situations in which there are plenty of objects to
shrink, but we can't do it because the __GFP_FS flag is not set.
Although they can happen with user pages, they are a lot more common
with fs-metadata: this is the case with almost all inode allocation.

For those cases, the best we can do is to spawn a worker and fail the
current allocation.

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/swap.h |    2 +
 mm/memcontrol.c      |  118 +++++++++++++++++++++++++++++++++++++++++++++++---
 mm/vmscan.c          |   44 ++++++++++++++++++-
 3 files changed, 157 insertions(+), 7 deletions(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 46ba0c6..367a773 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -309,6 +309,8 @@ extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
 extern int __isolate_lru_page(struct page *page, isolate_mode_t mode);
 extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem,
 						  gfp_t gfp_mask, bool noswap);
+extern unsigned long try_to_free_mem_cgroup_kmem(struct mem_cgroup *mem,
+						 gfp_t gfp_mask);
 extern unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
 						gfp_t gfp_mask, bool noswap,
 						struct zone *zone,
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index bb38596..f5b9921 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -328,6 +328,8 @@ struct mem_cgroup {
 	atomic_t	numainfo_events;
 	atomic_t	numainfo_updating;
 #endif
+	/* when kmem shrinkers can sleep but can't proceed due to context */
+	struct work_struct kmemcg_shrink_work;
 
 	struct mem_cgroup_per_node *nodeinfo[0];
 	/* WARNING: nodeinfo must be the last member here */
@@ -339,11 +341,14 @@ static size_t memcg_size(void)
 		nr_node_ids * sizeof(struct mem_cgroup_per_node);
 }
 
+static DEFINE_MUTEX(set_limit_mutex);
+
 /* internal only representation about the status of kmem accounting. */
 enum {
 	KMEM_ACCOUNTED_ACTIVE = 0, /* accounted by this cgroup itself */
 	KMEM_ACCOUNTED_ACTIVATED, /* static key enabled. */
 	KMEM_ACCOUNTED_DEAD, /* dead memcg with pending kmem charges */
+	KMEM_MAY_SHRINK, /* kmem limit < mem limit, shrink kmem only */
 };
 
 /* We account when limit is on, but only after call sites are patched */
@@ -387,6 +392,31 @@ static bool memcg_kmem_test_and_clear_dead(struct mem_cgroup *memcg)
 	return test_and_clear_bit(KMEM_ACCOUNTED_DEAD,
 				  &memcg->kmem_account_flags);
 }
+
+/*
+ * If the kernel limit is smaller than the user limit, we will have situations
+ * in which our allocations fail but freeing user pages will buy us nothing.
+ * In those, we would like to call a specialized memcg reclaimer that only
+ * frees kernel memory and leaves the user memory alone.
+ *
+ * This test exists so we can differentiate between those. Every time one of the
+ * limits is updated, we need to run it. The set_limit_mutex must be held, so
+ * they don't change again.
+ */
+static void memcg_update_shrink_status(struct mem_cgroup *memcg)
+{
+	mutex_lock(&set_limit_mutex);
+	if (res_counter_read_u64(&memcg->kmem, RES_LIMIT) <
+		res_counter_read_u64(&memcg->res, RES_LIMIT))
+		set_bit(KMEM_MAY_SHRINK, &memcg->kmem_account_flags);
+	else
+		clear_bit(KMEM_MAY_SHRINK, &memcg->kmem_account_flags);
+	mutex_unlock(&set_limit_mutex);
+}
+#else
+static void memcg_update_shrink_status(struct mem_cgroup *memcg)
+{
+}
 #endif
 
 /* Stuffs for move charges at task migration. */
@@ -2941,8 +2971,6 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg,
 	memcg_check_events(memcg, page);
 }
 
-static DEFINE_MUTEX(set_limit_mutex);
-
 #ifdef CONFIG_MEMCG_KMEM
 static inline bool memcg_can_account_kmem(struct mem_cgroup *memcg)
 {
@@ -3039,16 +3067,55 @@ static int mem_cgroup_slabinfo_read(struct cgroup_subsys_state *css,
 }
 #endif
 
+static int memcg_try_charge_kmem(struct mem_cgroup *memcg, gfp_t gfp, u64 size)
+{
+	int retries = MEM_CGROUP_RECLAIM_RETRIES;
+	struct res_counter *fail_res;
+	int ret;
+
+	do {
+		ret = res_counter_charge(&memcg->kmem, size, &fail_res);
+		if (!ret)
+			return ret;
+
+		/*
+		 * We will try to shrink kernel memory present in caches.  If
+		 * we can't wait, we will have no option rather than fail the
+		 * current allocation and make room in the background hoping
+		 * the next one will succeed.
+		 *
+		 * If we are in FS context, then although we can wait,
+		 * we cannot call the shrinkers. Most fs shrinkers will not run
+		 * without __GFP_FS since they can deadlock.
+		 */
+		if (!(gfp & __GFP_WAIT) || !(gfp & __GFP_FS)) {
+			/*
+			 * we are already short on memory, every queue
+			 * allocation is likely to fail.
+			 */
+			memcg_stop_kmem_account();
+			schedule_work(&memcg->kmemcg_shrink_work);
+			memcg_resume_kmem_account();
+		} else
+			try_to_free_mem_cgroup_kmem(memcg, gfp);
+	} while (retries--);
+
+	return ret;
+}
+
 static int memcg_charge_kmem(struct mem_cgroup *memcg, gfp_t gfp, u64 size)
 {
 	struct res_counter *fail_res;
 	struct mem_cgroup *_memcg;
 	int ret = 0;
 	bool may_oom;
+	bool kmem_first = test_bit(KMEM_MAY_SHRINK, &memcg->kmem_account_flags);
 
-	ret = res_counter_charge(&memcg->kmem, size, &fail_res);
-	if (ret)
-		return ret;
+	if (kmem_first) {
+		ret = memcg_try_charge_kmem(memcg, gfp, size);
+		if (ret)
+			return ret;
+	}
 
 	/*
 	 * Conditions under which we can wait for the oom_killer. Those are
@@ -3080,13 +3147,47 @@ static int memcg_charge_kmem(struct mem_cgroup *memcg, gfp_t gfp, u64 size)
 		if (do_swap_account)
 			res_counter_charge_nofail(&memcg->memsw, size,
 						  &fail_res);
+		if (!kmem_first)
+			res_counter_charge_nofail(&memcg->kmem, size, &fail_res);
 		ret = 0;
-	} else if (ret)
+	} else if (ret && kmem_first)
 		res_counter_uncharge(&memcg->kmem, size);
 
+	if (!ret && !kmem_first) {
+		ret = res_counter_charge(&memcg->kmem, size, &fail_res);
+		if (!ret)
+			return ret;
+
+		res_counter_uncharge(&memcg->res, size);
+		if (do_swap_account)
+			res_counter_uncharge(&memcg->memsw, size);
+	}
+
 	return ret;
 }
 
+/*
+ * There might be situations in which there are plenty of objects to shrink,
+ * but we can't do it because the __GFP_FS flag is not set.  This is the case
+ * with almost all inode allocation. Unfortunately we have no idea which fs
+ * locks we are holding to put ourselves in this situation, so the best we
+ * can do is to spawn a worker, fail the current allocation and hope that
+ * the next one succeeds.
+ *
+ * One way to make it better is to introduce some sort of implicit soft-limit
+ * that would trigger background reclaim for memcg when we are close to the
+ * kmem limit, so that we would never have to be faced with direct reclaim
+ * potentially lacking __GFP_FS.
+ */
+static void kmemcg_shrink_work_fn(struct work_struct *w)
+{
+	struct mem_cgroup *memcg;
+
+	memcg = container_of(w, struct mem_cgroup, kmemcg_shrink_work);
+	try_to_free_mem_cgroup_kmem(memcg, GFP_KERNEL);
+}
+
+
 static void memcg_uncharge_kmem(struct mem_cgroup *memcg, u64 size)
 {
 	res_counter_uncharge(&memcg->res, size);
@@ -5287,6 +5388,8 @@ static int mem_cgroup_write(struct cgroup_subsys_state *css, struct cftype *cft,
 			ret = memcg_update_kmem_limit(css, val);
 		else
 			return -EINVAL;
+		if (!ret)
+			memcg_update_shrink_status(memcg);
 		break;
 	case RES_SOFT_LIMIT:
 		ret = res_counter_memparse_write_strategy(buffer, &val);
@@ -5915,6 +6018,7 @@ static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
 	int ret;
 
 	INIT_LIST_HEAD(&memcg->memcg_slab_caches);
+	INIT_WORK(&memcg->kmemcg_shrink_work, kmemcg_shrink_work_fn);
 	mutex_init(&memcg->slab_caches_mutex);
 	memcg->kmemcg_id = -1;
 	ret = memcg_propagate_kmem(memcg);
@@ -5934,6 +6038,8 @@ static void kmem_cgroup_css_offline(struct mem_cgroup *memcg)
 	if (!memcg_kmem_is_active(memcg))
 		return;
 
+	cancel_work_sync(&memcg->kmemcg_shrink_work);
+
 	/*
 	 * kmem charges can outlive the cgroup. In the case of slab
 	 * pages, for instance, a page contain objects from various
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 652dfa3..cdfc364 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2730,7 +2730,49 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
 
 	return nr_reclaimed;
 }
-#endif
+
+#ifdef CONFIG_MEMCG_KMEM
+/*
+ * This function is called when we are under kmem-specific pressure.  It will
+ * only trigger in environments with kmem.limit_in_bytes < limit_in_bytes, IOW,
+ * with a lower kmem allowance than the memory allowance.
+ *
+ * In this situation, freeing user pages from the cgroup won't do us any good.
+ * What we really need is to call the memcg-aware shrinkers, in the hope of
+ * freeing pages holding kmem objects. It may also be that we won't be able to
+ * free any pages, but will get rid of old objects opening up space for new
+ * ones.
+ */
+unsigned long try_to_free_mem_cgroup_kmem(struct mem_cgroup *memcg,
+					  gfp_t gfp_mask)
+{
+	long freed;
+
+	struct shrink_control shrink = {
+		.gfp_mask = gfp_mask,
+		.target_mem_cgroup = memcg,
+	};
+
+	if (!(gfp_mask & __GFP_WAIT))
+		return 0;
+
+	/*
+	 * memcg pressure is always global */
+	nodes_setall(shrink.nodes_to_scan);
+
+	/*
+	 * We haven't scanned any user LRU, so we basically come up with
+	 * crafted values of nr_scanned and LRU page (1 and 0 respectively).
+	 * This should be enough to tell shrink_slab that the freeing
+	 * responsibility is all on himself.
+	 */
+	freed = shrink_slab(&shrink, 1, 0);
+	if (!freed)
+		congestion_wait(BLK_RW_ASYNC, HZ/10);
+	return freed;
+}
+#endif /* CONFIG_MEMCG_KMEM */
+#endif /* CONFIG_MEMCG */
 
 static void age_active_anon(struct zone *zone, struct scan_control *sc)
 {
-- 
1.7.10.4

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[PATCH v11 07/15] memcg: scan cache objects hierarchically

[Vladimir Davydov]

From: Glauber Costa <glommer@openvz.org>

When reaching shrink_slab, we should descent in children memcg searching
for objects that could be shrunk. This is true even if the memcg does
not have kmem limits on, since the kmem res_counter will also be billed
against the user res_counter of the parent.

It is possible that we will free objects and not free any pages, that
will just harm the child groups without helping the parent group at all.
But at this point, we basically are prepared to pay the price.

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 |    6 ++++
 mm/memcontrol.c            |   13 +++++++++
 mm/vmscan.c                |   65 ++++++++++++++++++++++++++++++++++++--------
 3 files changed, 73 insertions(+), 11 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index d16ba51..a513fad 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -488,6 +488,7 @@ static inline bool memcg_kmem_enabled(void)
 	return static_key_false(&memcg_kmem_enabled_key);
 }
 
+bool memcg_kmem_should_reclaim(struct mem_cgroup *memcg);
 bool memcg_kmem_is_active(struct mem_cgroup *memcg);
 
 /*
@@ -624,6 +625,11 @@ memcg_kmem_get_cache(struct kmem_cache *cachep, gfp_t gfp)
 }
 #else
 
+static inline bool memcg_kmem_should_reclaim(struct mem_cgroup *memcg)
+{
+	return false;
+}
+
 static inline bool memcg_kmem_is_active(struct mem_cgroup *memcg)
 {
 	return false;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f5b9921..2f5a777 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2972,6 +2972,19 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg,
 }
 
 #ifdef CONFIG_MEMCG_KMEM
+bool memcg_kmem_should_reclaim(struct mem_cgroup *memcg)
+{
+	struct mem_cgroup *iter;
+
+	for_each_mem_cgroup_tree(iter, memcg) {
+		if (memcg_kmem_is_active(iter)) {
+			mem_cgroup_iter_break(memcg, iter);
+			return true;
+		}
+	}
+	return false;
+}
+
 static inline bool memcg_can_account_kmem(struct mem_cgroup *memcg)
 {
 	return !mem_cgroup_disabled() && !mem_cgroup_is_root(memcg) &&
diff --git a/mm/vmscan.c b/mm/vmscan.c
index cdfc364..36fc133 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -149,7 +149,7 @@ static bool global_reclaim(struct scan_control *sc)
 static bool has_kmem_reclaim(struct scan_control *sc)
 {
 	return !sc->target_mem_cgroup ||
-		memcg_kmem_is_active(sc->target_mem_cgroup);
+		memcg_kmem_should_reclaim(sc->target_mem_cgroup);
 }
 
 static unsigned long
@@ -360,12 +360,35 @@ shrink_slab_node(struct shrink_control *shrinkctl, struct shrinker *shrinker,
  *
  * Returns the number of slab objects which we shrunk.
  */
+static unsigned long
+shrink_slab_one(struct shrink_control *shrinkctl, struct shrinker *shrinker,
+		unsigned long nr_pages_scanned, unsigned long lru_pages)
+{
+	unsigned long freed = 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,
+			 nr_pages_scanned, lru_pages);
+
+	}
+
+	return freed;
+}
+
 unsigned long shrink_slab(struct shrink_control *shrinkctl,
 			  unsigned long nr_pages_scanned,
 			  unsigned long lru_pages)
 {
 	struct shrinker *shrinker;
 	unsigned long freed = 0;
+	struct mem_cgroup *root = shrinkctl->target_mem_cgroup;
 
 	if (nr_pages_scanned == 0)
 		nr_pages_scanned = SWAP_CLUSTER_MAX;
@@ -390,19 +413,39 @@ unsigned long shrink_slab(struct shrink_control *shrinkctl,
 		if (shrinkctl->target_mem_cgroup &&
 		    !(shrinker->flags & SHRINKER_MEMCG_AWARE))
 			continue;
+		/*
+		 * In a hierarchical chain, it might be that not all memcgs are
+		 * kmem active. kmemcg design mandates that when one memcg is
+		 * active, its children will be active as well. But it is
+		 * perfectly possible that its parent is not.
+		 *
+		 * We also need to make sure we scan at least once, for the
+		 * global case. So if we don't have a target memcg (saved in
+		 * root), we proceed normally and expect to break in the next
+		 * round.
+		 */
+		do {
+			struct mem_cgroup *memcg = shrinkctl->target_mem_cgroup;
 
-		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))
+			if (!memcg || memcg_kmem_is_active(memcg))
+				freed += shrink_slab_one(shrinkctl, shrinker,
+					 nr_pages_scanned, lru_pages);
+			/*
+			 * For non-memcg aware shrinkers, we will arrive here
+			 * at first pass because we need to scan the root
+			 * memcg.  We need to bail out, since exactly because
+			 * they are not memcg aware, instead of noticing they
+			 * have nothing to shrink, they will just shrink again,
+			 * and deplete too many objects.
+			 */
+			if (!(shrinker->flags & SHRINKER_MEMCG_AWARE))
 				break;
+			shrinkctl->target_mem_cgroup =
+				mem_cgroup_iter(root, memcg, NULL);
+		} while (shrinkctl->target_mem_cgroup);
 
-			freed += shrink_slab_node(shrinkctl, shrinker,
-				 nr_pages_scanned, lru_pages);
-
-		}
+		/* restore original state */
+		shrinkctl->target_mem_cgroup = root;
 	}
 	up_read(&shrinker_rwsem);
 out:
-- 
1.7.10.4

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[PATCH v11 08/15] vmscan: take at least one pass with shrinkers

[Vladimir Davydov]

From: Glauber Costa <glommer@openvz.org>

In very low free kernel memory situations, it may be the case that we
have less objects to free than our initial batch size. If this is the
case, it is better to shrink those, and open space for the new workload
then to keep them and fail the new allocations.

In particular, we are concerned with the direct reclaim case for memcg.
Although this same technique can be applied to other situations just as well,
we will start conservative and apply it for that case, which is the one
that matters the most.

Signed-off-by: Glauber Costa <glommer@openvz.org>
CC: Dave Chinner <dchinner@redhat.com>
CC: Carlos Maiolino <cmaiolino@redhat.com>
CC: "Theodore Ts'o" <tytso@mit.edu>
CC: Al Viro <viro@zeniv.linux.org.uk>
---
 mm/vmscan.c |   23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 36fc133..bfedcdc 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -311,20 +311,33 @@ shrink_slab_node(struct shrink_control *shrinkctl, struct shrinker *shrinker,
 				nr_pages_scanned, lru_pages,
 				max_pass, delta, total_scan);
 
-	while (total_scan >= batch_size) {
+	do {
 		unsigned long ret;
+		unsigned long nr_to_scan = min(batch_size, total_scan);
+		struct mem_cgroup *memcg = shrinkctl->target_mem_cgroup;
+
+		/*
+		 * Differentiate between "few objects" and "no objects"
+		 * as returned by the count step.
+		 */
+		if (!total_scan)
+			break;
+
+		if ((total_scan < batch_size) &&
+		   !(memcg && memcg_kmem_is_active(memcg)))
+			break;
 
-		shrinkctl->nr_to_scan = batch_size;
+		shrinkctl->nr_to_scan = nr_to_scan;
 		ret = shrinker->scan_objects(shrinker, shrinkctl);
 		if (ret == SHRINK_STOP)
 			break;
 		freed += ret;
 
-		count_vm_events(SLABS_SCANNED, batch_size);
-		total_scan -= batch_size;
+		count_vm_events(SLABS_SCANNED, nr_to_scan);
+		total_scan -= nr_to_scan;
 
 		cond_resched();
-	}
+	} while (total_scan >= batch_size);
 
 	/*
 	 * move the unused scan count back into the shrinker in a
-- 
1.7.10.4

--
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[PATCH v11 09/15] memcg,list_lru: add per-memcg LRU list infrastructure

[Vladimir Davydov]

FS-shrinkers, which shrink dcaches and icaches, keep dentries and inodes
in list_lru structures in order to evict least recently used objects.
With per-memcg kmem shrinking infrastructure introduced, we have to make
those LRU lists per-memcg in order to allow shrinking FS caches that
belong to different memory cgroups independently.

This patch addresses the issue by introducing struct memcg_list_lru.
This struct aggregates list_lru objects for each kmem-active memcg, and
keeps it uptodate whenever a memcg is created or destroyed. Its
interface is very simple: it only allows to get the pointer to the
appropriate list_lru object from a memcg or a kmem ptr, which should be
further operated with conventional list_lru methods.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: 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/list_lru.h |   56 +++++++++++
 mm/memcontrol.c          |  251 ++++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 301 insertions(+), 6 deletions(-)

diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
index 3ce5417..b3b3b86 100644
--- a/include/linux/list_lru.h
+++ b/include/linux/list_lru.h
@@ -10,6 +10,8 @@
 #include <linux/list.h>
 #include <linux/nodemask.h>
 
+struct mem_cgroup;
+
 /* list_lru_walk_cb has to always return one of those */
 enum lru_status {
 	LRU_REMOVED,		/* item removed from list */
@@ -31,6 +33,27 @@ struct list_lru {
 	nodemask_t		active_nodes;
 };
 
+struct memcg_list_lru {
+	struct list_lru global_lru;
+
+#ifdef CONFIG_MEMCG_KMEM
+	struct list_lru **memcg_lrus;	/* rcu-protected array of per-memcg
+					   lrus, indexed by memcg_cache_id() */
+
+	struct list_head list;		/* list of all memcg-aware lrus */
+
+	/*
+	 * The memcg_lrus array is rcu protected, so we can only free it after
+	 * a call to synchronize_rcu(). To avoid multiple calls to
+	 * synchronize_rcu() when many lrus get updated at the same time, which
+	 * is a typical scenario, we will store the pointer to the previous
+	 * version of the array in the old_lrus variable for each lru, and then
+	 * free them all at once after a single call to synchronize_rcu().
+	 */
+	void *old_lrus;
+#endif
+};
+
 void list_lru_destroy(struct list_lru *lru);
 int list_lru_init(struct list_lru *lru);
 
@@ -128,4 +151,37 @@ list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
 	}
 	return isolated;
 }
+
+#ifdef CONFIG_MEMCG_KMEM
+int memcg_list_lru_init(struct memcg_list_lru *lru);
+void memcg_list_lru_destroy(struct memcg_list_lru *lru);
+
+struct list_lru *
+mem_cgroup_list_lru(struct memcg_list_lru *lru, struct mem_cgroup *memcg);
+struct list_lru *
+mem_cgroup_kmem_list_lru(struct memcg_list_lru *lru, void *ptr);
+#else
+static inline int memcg_list_lru_init(struct memcg_list_lru *lru)
+{
+	return list_lru_init(&lru->global_lru);
+}
+
+static inline void memcg_list_lru_destroy(struct memcg_list_lru *lru)
+{
+	list_lru_destroy(&lru->global_lru);
+}
+
+static inline struct list_lru *
+mem_cgroup_list_lru(struct memcg_list_lru *lru, struct mem_cgroup *memcg)
+{
+	return &lru->global_lru;
+}
+
+static inline struct list_lru *
+mem_cgroup_kmem_list_lru(struct memcg_list_lru *lru, void *ptr)
+{
+	return &lru->global_lru;
+}
+#endif /* CONFIG_MEMCG_KMEM */
+
 #endif /* _LRU_LIST_H */
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2f5a777..39e4772 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -54,6 +54,7 @@
 #include <linux/page_cgroup.h>
 #include <linux/cpu.h>
 #include <linux/oom.h>
+#include <linux/list_lru.h>
 #include "internal.h"
 #include <net/sock.h>
 #include <net/ip.h>
@@ -3233,6 +3234,8 @@ void memcg_cache_list_add(struct mem_cgroup *memcg, struct kmem_cache *cachep)
 	mutex_unlock(&memcg->slab_caches_mutex);
 }
 
+static int memcg_update_all_lrus(int num_groups);
+
 /*
  * This ends up being protected by the set_limit mutex, during normal
  * operation, because that is its main call site.
@@ -3257,15 +3260,28 @@ int memcg_update_cache_sizes(struct mem_cgroup *memcg)
 	 */
 	memcg_kmem_set_activated(memcg);
 
-	ret = memcg_update_all_caches(num+1);
-	if (ret) {
-		ida_simple_remove(&kmem_limited_groups, num);
-		memcg_kmem_clear_activated(memcg);
-		return ret;
-	}
+	/*
+	 * We need to update the memcg lru lists before we update the caches.
+	 * Once the caches are updated, they will be able to start hosting
+	 * objects. If a cache is created very quickly and an element is used
+	 * and disposed to the lru quickly as well, we can end up with a NULL
+	 * pointer dereference while trying to add a new element to a memcg
+	 * lru.
+	 */
+	ret = memcg_update_all_lrus(num + 1);
+	if (ret)
+		goto out;
+
+	ret = memcg_update_all_caches(num + 1);
+	if (ret)
+		goto out;
 
 	memcg->kmemcg_id = num;
 	return 0;
+out:
+	ida_simple_remove(&kmem_limited_groups, num);
+	memcg_kmem_clear_activated(memcg);
+	return ret;
 }
 
 static size_t memcg_caches_array_size(int num_groups)
@@ -3865,6 +3881,228 @@ void __memcg_kmem_uncharge_pages(struct page *page, int order)
 	VM_BUG_ON(mem_cgroup_is_root(memcg));
 	memcg_uncharge_kmem(memcg, PAGE_SIZE << order);
 }
+
+static LIST_HEAD(memcg_lrus_list);
+
+static int alloc_memcg_lru(struct memcg_list_lru *lru, int memcg_id)
+{
+	int err;
+	struct list_lru *memcg_lru;
+
+	memcg_lru = kmalloc(sizeof(*memcg_lru), GFP_KERNEL);
+	if (!memcg_lru)
+		return -ENOMEM;
+
+	err = list_lru_init(memcg_lru);
+	if (err) {
+		kfree(memcg_lru);
+		return err;
+	}
+
+	VM_BUG_ON(lru->memcg_lrus[memcg_id]);
+	lru->memcg_lrus[memcg_id] = memcg_lru;
+	return 0;
+}
+
+static void free_memcg_lru(struct memcg_list_lru *lru, int memcg_id)
+{
+	struct list_lru *memcg_lru = NULL;
+
+	swap(lru->memcg_lrus[memcg_id], memcg_lru);
+	if (memcg_lru) {
+		list_lru_destroy(memcg_lru);
+		kfree(memcg_lru);
+	}
+}
+
+static int memcg_list_lru_grow(struct memcg_list_lru *lru, int num_groups)
+{
+	struct list_lru **new_lrus;
+
+	new_lrus = kcalloc(memcg_caches_array_size(num_groups),
+			   sizeof(*new_lrus), GFP_KERNEL);
+	if (!new_lrus)
+		return -ENOMEM;
+
+	if (lru->memcg_lrus) {
+		int i;
+
+		for (i = 0; i < memcg_limited_groups_array_size; i++) {
+			if (lru->memcg_lrus[i])
+				new_lrus[i] = lru->memcg_lrus[i];
+		}
+	}
+
+	lru->old_lrus = lru->memcg_lrus;
+	rcu_assign_pointer(lru->memcg_lrus, new_lrus);
+	return 0;
+}
+
+static void __memcg_destroy_all_lrus(int memcg_id)
+{
+	struct memcg_list_lru *lru;
+
+	list_for_each_entry(lru, &memcg_lrus_list, list)
+		free_memcg_lru(lru, memcg_id);
+}
+
+static void memcg_destroy_all_lrus(struct mem_cgroup *memcg)
+{
+	int memcg_id;
+
+	memcg_id = memcg_cache_id(memcg);
+	if (memcg_id >= 0) {
+		mutex_lock(&memcg_create_mutex);
+		__memcg_destroy_all_lrus(memcg_id);
+		mutex_unlock(&memcg_create_mutex);
+	}
+}
+
+static int memcg_update_all_lrus(int num_groups)
+{
+	int err = 0;
+	struct memcg_list_lru *lru;
+	int new_memcg_id = num_groups - 1;
+	int grow = (num_groups > memcg_limited_groups_array_size);
+
+	memcg_stop_kmem_account();
+	if (grow) {
+		list_for_each_entry(lru, &memcg_lrus_list, list) {
+			err = memcg_list_lru_grow(lru, num_groups);
+			if (err)
+				goto out;
+		}
+	}
+	list_for_each_entry(lru, &memcg_lrus_list, list) {
+		err = alloc_memcg_lru(lru, new_memcg_id);
+		if (err)
+			goto out;
+	}
+out:
+	if (grow) {
+		/* free previous versions of memcg_lrus arrays */
+		synchronize_rcu();
+		list_for_each_entry(lru, &memcg_lrus_list, list) {
+			kfree(lru->old_lrus);
+			lru->old_lrus = NULL;
+		}
+	}
+	if (err)
+		__memcg_destroy_all_lrus(new_memcg_id);
+	memcg_resume_kmem_account();
+	return err;
+}
+
+static void __memcg_list_lru_destroy(struct memcg_list_lru *lru)
+{
+	int i;
+
+	if (lru->memcg_lrus) {
+		for (i = 0; i < memcg_limited_groups_array_size; i++)
+			free_memcg_lru(lru, i);
+	}
+}
+
+static int __memcg_list_lru_init(struct memcg_list_lru *lru)
+{
+	int err = 0;
+	struct mem_cgroup *memcg;
+
+	if (!memcg_kmem_enabled())
+		return 0;
+
+	memcg_stop_kmem_account();
+	lru->memcg_lrus = kcalloc(memcg_limited_groups_array_size,
+				  sizeof(*lru->memcg_lrus), GFP_KERNEL);
+	if (!lru->memcg_lrus)
+		return -ENOMEM;
+
+	for_each_mem_cgroup(memcg) {
+		int memcg_id;
+
+		memcg_id = memcg_cache_id(memcg);
+		if (memcg_id < 0)
+			continue;
+
+		err = alloc_memcg_lru(lru, memcg_id);
+		if (err) {
+			mem_cgroup_iter_break(root_mem_cgroup, memcg);
+			goto out;
+		}
+	}
+out:
+	if (err)
+		__memcg_list_lru_destroy(lru);
+	memcg_resume_kmem_account();
+	return err;
+}
+
+int memcg_list_lru_init(struct memcg_list_lru *lru)
+{
+	int err;
+
+	memset(lru, 0, sizeof(*lru));
+
+	err = list_lru_init(&lru->global_lru);
+	if (err)
+		return err;
+
+	mutex_lock(&memcg_create_mutex);
+	err = __memcg_list_lru_init(lru);
+	if (!err)
+		list_add(&lru->list, &memcg_lrus_list);
+	mutex_unlock(&memcg_create_mutex);
+
+	if (err)
+		list_lru_destroy(&lru->global_lru);
+	return err;
+}
+
+void memcg_list_lru_destroy(struct memcg_list_lru *lru)
+{
+	list_lru_destroy(&lru->global_lru);
+
+	mutex_lock(&memcg_create_mutex);
+	__memcg_list_lru_destroy(lru);
+	list_del(&lru->list);
+	mutex_unlock(&memcg_create_mutex);
+}
+
+struct list_lru *
+mem_cgroup_list_lru(struct memcg_list_lru *lru, struct mem_cgroup *memcg)
+{
+	struct list_lru **memcg_lrus;
+	struct list_lru *memcg_lru;
+	int memcg_id;
+
+	memcg_id = memcg_cache_id(memcg);
+	if (memcg_id < 0)
+		return &lru->global_lru;
+
+	rcu_read_lock();
+	memcg_lrus = rcu_dereference(lru->memcg_lrus);
+	memcg_lru = memcg_lrus[memcg_id];
+	rcu_read_unlock();
+
+	return memcg_lru;
+}
+
+struct list_lru *
+mem_cgroup_kmem_list_lru(struct memcg_list_lru *lru, void *ptr)
+{
+	struct page *page = virt_to_page(ptr);
+	struct mem_cgroup *memcg = NULL;
+	struct page_cgroup *pc;
+
+	pc = lookup_page_cgroup(compound_head(page));
+	if (PageCgroupUsed(pc)) {
+		lock_page_cgroup(pc);
+		if (PageCgroupUsed(pc))
+			memcg = pc->mem_cgroup;
+		unlock_page_cgroup(pc);
+	}
+	return mem_cgroup_list_lru(lru, memcg);
+}
 #else
 static inline void mem_cgroup_destroy_all_caches(struct mem_cgroup *memcg)
 {
@@ -6044,6 +6282,7 @@ static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
 static void memcg_destroy_kmem(struct mem_cgroup *memcg)
 {
 	mem_cgroup_sockets_destroy(memcg);
+	memcg_destroy_all_lrus(memcg);
 }
 
 static void kmem_cgroup_css_offline(struct mem_cgroup *memcg)
-- 
1.7.10.4

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[PATCH v11 10/15] memcg,list_lru: add function walking over all lists of a per-memcg LRU

[Vladimir Davydov]

Sometimes it can be necessary to iterate over all memcgs' lists of the
same memcg-aware LRU. For example shrink_dcache_sb() should prune all
dentries no matter what memory cgroup they belong to. Current interface
to struct memcg_list_lru, however, only allows per-memcg LRU walks.
This patch adds the special method memcg_list_lru_walk_all() which
provides the required functionality. Note that this function does not
guarantee that all the elements will be processed in the true
least-recently-used order, in fact it simply enumerates all kmem-active
memcgs and for each of them calls list_lru_walk(), but
shrink_dcache_sb(), which is going to be the only user of this function,
does not need it.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: 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/list_lru.h |   21 ++++++++++++++++++
 mm/memcontrol.c          |   55 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 76 insertions(+)

diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
index b3b3b86..ce815cc 100644
--- a/include/linux/list_lru.h
+++ b/include/linux/list_lru.h
@@ -40,6 +40,16 @@ struct memcg_list_lru {
 	struct list_lru **memcg_lrus;	/* rcu-protected array of per-memcg
 					   lrus, indexed by memcg_cache_id() */
 
+	/*
+	 * When a memory cgroup is removed, all pointers to its list_lru
+	 * objects stored in memcg_lrus arrays are first marked as dead by
+	 * setting the lowest bit of the address while the actual data free
+	 * happens only after an rcu grace period. If a memcg_lrus reader,
+	 * which should be rcu-protected, faces a dead pointer, it won't
+	 * dereference it. This ensures there will be no use-after-free.
+	 */
+#define MEMCG_LIST_LRU_DEAD		1
+
 	struct list_head list;		/* list of all memcg-aware lrus */
 
 	/*
@@ -160,6 +170,10 @@ struct list_lru *
 mem_cgroup_list_lru(struct memcg_list_lru *lru, struct mem_cgroup *memcg);
 struct list_lru *
 mem_cgroup_kmem_list_lru(struct memcg_list_lru *lru, void *ptr);
+
+unsigned long
+memcg_list_lru_walk_all(struct memcg_list_lru *lru, list_lru_walk_cb isolate,
+			void *cb_arg, unsigned long nr_to_walk);
 #else
 static inline int memcg_list_lru_init(struct memcg_list_lru *lru)
 {
@@ -182,6 +196,13 @@ mem_cgroup_kmem_list_lru(struct memcg_list_lru *lru, void *ptr)
 {
 	return &lru->global_lru;
 }
+
+static inline unsigned long
+memcg_list_lru_walk_all(struct memcg_list_lru *lru, list_lru_walk_cb isolate,
+			void *cb_arg, unsigned long nr_to_walk)
+{
+	return list_lru_walk(&lru->global_lru, isolate, cb_arg, nr_to_walk);
+}
 #endif /* CONFIG_MEMCG_KMEM */
 
 #endif /* _LRU_LIST_H */
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 39e4772..03178d0 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3899,16 +3899,30 @@ static int alloc_memcg_lru(struct memcg_list_lru *lru, int memcg_id)
 		return err;
 	}
 
+	smp_wmb();
 	VM_BUG_ON(lru->memcg_lrus[memcg_id]);
 	lru->memcg_lrus[memcg_id] = memcg_lru;
 	return 0;
 }
 
+static void memcg_lru_mark_dead(struct memcg_list_lru *lru, int memcg_id)
+{
+	struct list_lru *memcg_lru;
+	
+	BUG_ON(!lru->memcg_lrus);
+	memcg_lru = lru->memcg_lrus[memcg_id];
+	if (memcg_lru)
+		lru->memcg_lrus[memcg_id] = (void *)((unsigned long)memcg_lru |
+						     MEMCG_LIST_LRU_DEAD);
+}
+
 static void free_memcg_lru(struct memcg_list_lru *lru, int memcg_id)
 {
 	struct list_lru *memcg_lru = NULL;
 
 	swap(lru->memcg_lrus[memcg_id], memcg_lru);
+	memcg_lru = (void *)((unsigned long)memcg_lru &
+			     ~MEMCG_LIST_LRU_DEAD);
 	if (memcg_lru) {
 		list_lru_destroy(memcg_lru);
 		kfree(memcg_lru);
@@ -3942,6 +3956,17 @@ static void __memcg_destroy_all_lrus(int memcg_id)
 {
 	struct memcg_list_lru *lru;
 
+	/*
+	 * Mark all lru lists of this memcg as dead and free them only after a
+	 * grace period. This is to prevent functions iterating over memcg_lrus
+	 * arrays (e.g. memcg_list_lru_walk_all()) from dereferencing pointers
+	 * pointing to already freed data.
+	 */
+	list_for_each_entry(lru, &memcg_lrus_list, list)
+		memcg_lru_mark_dead(lru, memcg_id);
+
+	synchronize_rcu();
+
 	list_for_each_entry(lru, &memcg_lrus_list, list)
 		free_memcg_lru(lru, memcg_id);
 }
@@ -4103,6 +4128,36 @@ mem_cgroup_kmem_list_lru(struct memcg_list_lru *lru, void *ptr)
 	}
 	return mem_cgroup_list_lru(lru, memcg);
 }
+
+unsigned long
+memcg_list_lru_walk_all(struct memcg_list_lru *lru, list_lru_walk_cb isolate,
+			void *cb_arg, unsigned long nr_to_walk)
+{
+	int i;
+	unsigned long isolated;
+	struct list_lru *memcg_lru;
+	struct list_lru **memcg_lrus;
+
+	isolated = list_lru_walk(&lru->global_lru, isolate, cb_arg, nr_to_walk);
+
+	rcu_read_lock();
+	memcg_lrus = rcu_dereference(lru->memcg_lrus);
+	for (i = 0; i < memcg_limited_groups_array_size; i++) {
+		memcg_lru = memcg_lrus[i];
+		if (!memcg_lru)
+			continue;
+
+		if ((unsigned long)memcg_lru & MEMCG_LIST_LRU_DEAD)
+			continue;
+
+		smp_read_barrier_depends();
+		isolated += list_lru_walk(memcg_lru,
+					  isolate, cb_arg, nr_to_walk);
+	}
+	rcu_read_unlock();
+
+	return isolated;
+}
 #else
 static inline void mem_cgroup_destroy_all_caches(struct mem_cgroup *memcg)
 {
-- 
1.7.10.4

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[PATCH v11 11/15] super: make icache, dcache shrinkers memcg-aware

[Vladimir Davydov]

Using the per-memcg LRU infrastructure introduced by previous patches,
this patch makes dcache and icache shrinkers memcg-aware. To achieve
that, it converts s_dentry_lru and s_inode_lru from list_lru to
memcg_list_lru and restricts the reclaim to per-memcg parts of the lists
in case of memcg pressure.

Other FS objects are currently ignored and only reclaimed on global
pressure, because their shrinkers are heavily FS-specific and can't be
converted to be memcg-aware so easily. However, we can pass on target
memcg to the FS layer and let it decide if per-memcg objects should be
reclaimed.

Note that with this patch applied we lose global LRU order, but it does
not appear to be a critical drawback, because global pressure should try
to balance the amount reclaimed from all memcgs. On the other hand,
preserving global LRU order would require an extra list_head added to
each dentry and inode, which seems to be too costly.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: 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>
---
 fs/dcache.c        |   25 +++++++++++++++----------
 fs/inode.c         |   16 ++++++++++------
 fs/internal.h      |    9 +++++----
 fs/super.c         |   47 +++++++++++++++++++++++++++++------------------
 include/linux/fs.h |    4 ++--
 5 files changed, 61 insertions(+), 40 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 4100030..c128dee 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -373,18 +373,24 @@ static void dentry_unlink_inode(struct dentry * dentry)
 #define D_FLAG_VERIFY(dentry,x) WARN_ON_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x))
 static void d_lru_add(struct dentry *dentry)
 {
+	struct list_lru *lru =
+		mem_cgroup_kmem_list_lru(&dentry->d_sb->s_dentry_lru, dentry);
+
 	D_FLAG_VERIFY(dentry, 0);
 	dentry->d_flags |= DCACHE_LRU_LIST;
 	this_cpu_inc(nr_dentry_unused);
-	WARN_ON_ONCE(!list_lru_add(&dentry->d_sb->s_dentry_lru, &dentry->d_lru));
+	WARN_ON_ONCE(!list_lru_add(lru, &dentry->d_lru));
 }
 
 static void d_lru_del(struct dentry *dentry)
 {
+	struct list_lru *lru =
+		mem_cgroup_kmem_list_lru(&dentry->d_sb->s_dentry_lru, dentry);
+
 	D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
 	dentry->d_flags &= ~DCACHE_LRU_LIST;
 	this_cpu_dec(nr_dentry_unused);
-	WARN_ON_ONCE(!list_lru_del(&dentry->d_sb->s_dentry_lru, &dentry->d_lru));
+	WARN_ON_ONCE(!list_lru_del(lru, &dentry->d_lru));
 }
 
 static void d_shrink_del(struct dentry *dentry)
@@ -1006,9 +1012,9 @@ dentry_lru_isolate(struct list_head *item, spinlock_t *lru_lock, void *arg)
 }
 
 /**
- * prune_dcache_sb - shrink the dcache
- * @sb: superblock
- * @nr_to_scan : number of entries to try to free
+ * prune_dcache_lru - shrink the dcache
+ * @lru: dentry lru list
+ * @nr_to_scan: number of entries to try to free
  * @nid: which node to scan for freeable entities
  *
  * Attempt to shrink the superblock dcache LRU by @nr_to_scan entries. This is
@@ -1018,14 +1024,13 @@ dentry_lru_isolate(struct list_head *item, spinlock_t *lru_lock, void *arg)
  * This function may fail to free any resources if all the dentries are in
  * use.
  */
-long prune_dcache_sb(struct super_block *sb, unsigned long nr_to_scan,
-		     int nid)
+long prune_dcache_lru(struct list_lru *lru, unsigned long nr_to_scan, int nid)
 {
 	LIST_HEAD(dispose);
 	long freed;
 
-	freed = list_lru_walk_node(&sb->s_dentry_lru, nid, dentry_lru_isolate,
-				       &dispose, &nr_to_scan);
+	freed = list_lru_walk_node(lru, nid, dentry_lru_isolate,
+				   &dispose, &nr_to_scan);
 	shrink_dentry_list(&dispose);
 	return freed;
 }
@@ -1065,7 +1070,7 @@ void shrink_dcache_sb(struct super_block *sb)
 	do {
 		LIST_HEAD(dispose);
 
-		freed = list_lru_walk(&sb->s_dentry_lru,
+		freed = memcg_list_lru_walk_all(&sb->s_dentry_lru,
 			dentry_lru_isolate_shrink, &dispose, UINT_MAX);
 
 		this_cpu_sub(nr_dentry_unused, freed);
diff --git a/fs/inode.c b/fs/inode.c
index b33ba8e..f2f29fa 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -402,7 +402,10 @@ EXPORT_SYMBOL(ihold);
 
 static void inode_lru_list_add(struct inode *inode)
 {
-	if (list_lru_add(&inode->i_sb->s_inode_lru, &inode->i_lru))
+	struct list_lru *lru =
+		mem_cgroup_kmem_list_lru(&inode->i_sb->s_inode_lru, inode);
+
+	if (list_lru_add(lru, &inode->i_lru))
 		this_cpu_inc(nr_unused);
 }
 
@@ -421,8 +424,10 @@ void inode_add_lru(struct inode *inode)
 
 static void inode_lru_list_del(struct inode *inode)
 {
+	struct list_lru *lru =
+		mem_cgroup_kmem_list_lru(&inode->i_sb->s_inode_lru, inode);
 
-	if (list_lru_del(&inode->i_sb->s_inode_lru, &inode->i_lru))
+	if (list_lru_del(lru, &inode->i_lru))
 		this_cpu_dec(nr_unused);
 }
 
@@ -748,14 +753,13 @@ inode_lru_isolate(struct list_head *item, spinlock_t *lru_lock, void *arg)
  * to trim from the LRU. Inodes to be freed are moved to a temporary list and
  * then are freed outside inode_lock by dispose_list().
  */
-long prune_icache_sb(struct super_block *sb, unsigned long nr_to_scan,
-		     int nid)
+long prune_icache_lru(struct list_lru *lru, unsigned long nr_to_scan, int nid)
 {
 	LIST_HEAD(freeable);
 	long freed;
 
-	freed = list_lru_walk_node(&sb->s_inode_lru, nid, inode_lru_isolate,
-				       &freeable, &nr_to_scan);
+	freed = list_lru_walk_node(lru, nid, inode_lru_isolate,
+				   &freeable, &nr_to_scan);
 	dispose_list(&freeable);
 	return freed;
 }
diff --git a/fs/internal.h b/fs/internal.h
index 513e0d8..3c99eda 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -16,6 +16,7 @@ struct file_system_type;
 struct linux_binprm;
 struct path;
 struct mount;
+struct list_lru;
 
 /*
  * block_dev.c
@@ -114,8 +115,8 @@ extern int open_check_o_direct(struct file *f);
  * inode.c
  */
 extern spinlock_t inode_sb_list_lock;
-extern long prune_icache_sb(struct super_block *sb, unsigned long nr_to_scan,
-			    int nid);
+extern long prune_icache_lru(struct list_lru *lru,
+			     unsigned long nr_to_scan, int nid);
 extern void inode_add_lru(struct inode *inode);
 
 /*
@@ -132,8 +133,8 @@ extern int invalidate_inodes(struct super_block *, bool);
  */
 extern struct dentry *__d_alloc(struct super_block *, const struct qstr *);
 extern int d_set_mounted(struct dentry *dentry);
-extern long prune_dcache_sb(struct super_block *sb, unsigned long nr_to_scan,
-			    int nid);
+extern long prune_dcache_lru(struct list_lru *lru,
+			     unsigned long nr_to_scan, int nid);
 
 /*
  * read_write.c
diff --git a/fs/super.c b/fs/super.c
index 0225c20..c551684 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -57,6 +57,9 @@ static unsigned long super_cache_scan(struct shrinker *shrink,
 				      struct shrink_control *sc)
 {
 	struct super_block *sb;
+	struct mem_cgroup *memcg;
+	struct list_lru *inode_lru;
+	struct list_lru *dentry_lru;
 	long	fs_objects = 0;
 	long	total_objects;
 	long	freed = 0;
@@ -64,6 +67,7 @@ static unsigned long super_cache_scan(struct shrinker *shrink,
 	long	inodes;
 
 	sb = container_of(shrink, struct super_block, s_shrink);
+	memcg = sc->target_mem_cgroup;
 
 	/*
 	 * Deadlock avoidance.  We may hold various FS locks, and we don't want
@@ -75,11 +79,14 @@ static unsigned long super_cache_scan(struct shrinker *shrink,
 	if (!grab_super_passive(sb))
 		return SHRINK_STOP;
 
-	if (sb->s_op->nr_cached_objects)
+	if (sb->s_op->nr_cached_objects && !memcg)
 		fs_objects = sb->s_op->nr_cached_objects(sb, sc->nid);
 
-	inodes = list_lru_count_node(&sb->s_inode_lru, sc->nid);
-	dentries = list_lru_count_node(&sb->s_dentry_lru, sc->nid);
+	inode_lru = mem_cgroup_list_lru(&sb->s_inode_lru, memcg);
+	dentry_lru = mem_cgroup_list_lru(&sb->s_dentry_lru, memcg);
+
+	inodes = list_lru_count_node(inode_lru, sc->nid);
+	dentries = list_lru_count_node(dentry_lru, sc->nid);
 	total_objects = dentries + inodes + fs_objects + 1;
 
 	/* proportion the scan between the caches */
@@ -90,8 +97,8 @@ static unsigned long super_cache_scan(struct shrinker *shrink,
 	 * prune the dcache first as the icache is pinned by it, then
 	 * prune the icache, followed by the filesystem specific caches
 	 */
-	freed = prune_dcache_sb(sb, dentries, sc->nid);
-	freed += prune_icache_sb(sb, inodes, sc->nid);
+	freed = prune_dcache_lru(dentry_lru, dentries, sc->nid);
+	freed += prune_icache_lru(inode_lru, inodes, sc->nid);
 
 	if (fs_objects) {
 		fs_objects = mult_frac(sc->nr_to_scan, fs_objects,
@@ -108,21 +115,25 @@ static unsigned long super_cache_count(struct shrinker *shrink,
 				       struct shrink_control *sc)
 {
 	struct super_block *sb;
+	struct mem_cgroup *memcg;
+	struct list_lru *inode_lru;
+	struct list_lru *dentry_lru;
 	long	total_objects = 0;
 
 	sb = container_of(shrink, struct super_block, s_shrink);
+	memcg = sc->target_mem_cgroup;
 
 	if (!grab_super_passive(sb))
 		return 0;
 
-	if (sb->s_op && sb->s_op->nr_cached_objects)
-		total_objects = sb->s_op->nr_cached_objects(sb,
-						 sc->nid);
+	if (sb->s_op && sb->s_op->nr_cached_objects && !memcg)
+		total_objects = sb->s_op->nr_cached_objects(sb, sc->nid);
+
+	inode_lru = mem_cgroup_list_lru(&sb->s_inode_lru, memcg);
+	dentry_lru = mem_cgroup_list_lru(&sb->s_dentry_lru, memcg);
 
-	total_objects += list_lru_count_node(&sb->s_dentry_lru,
-						 sc->nid);
-	total_objects += list_lru_count_node(&sb->s_inode_lru,
-						 sc->nid);
+	total_objects += list_lru_count_node(dentry_lru, sc->nid);
+	total_objects += list_lru_count_node(inode_lru, sc->nid);
 
 	total_objects = vfs_pressure_ratio(total_objects);
 	drop_super(sb);
@@ -196,9 +207,9 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags)
 		INIT_HLIST_BL_HEAD(&s->s_anon);
 		INIT_LIST_HEAD(&s->s_inodes);
 
-		if (list_lru_init(&s->s_dentry_lru))
+		if (memcg_list_lru_init(&s->s_dentry_lru))
 			goto err_out;
-		if (list_lru_init(&s->s_inode_lru))
+		if (memcg_list_lru_init(&s->s_inode_lru))
 			goto err_out_dentry_lru;
 
 		INIT_LIST_HEAD(&s->s_mounts);
@@ -236,13 +247,13 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags)
 		s->s_shrink.scan_objects = super_cache_scan;
 		s->s_shrink.count_objects = super_cache_count;
 		s->s_shrink.batch = 1024;
-		s->s_shrink.flags = SHRINKER_NUMA_AWARE;
+		s->s_shrink.flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE;
 	}
 out:
 	return s;
 
 err_out_dentry_lru:
-	list_lru_destroy(&s->s_dentry_lru);
+	memcg_list_lru_destroy(&s->s_dentry_lru);
 err_out:
 	security_sb_free(s);
 #ifdef CONFIG_SMP
@@ -264,8 +275,8 @@ out_free_sb:
  */
 static inline void destroy_super(struct super_block *s)
 {
-	list_lru_destroy(&s->s_dentry_lru);
-	list_lru_destroy(&s->s_inode_lru);
+	memcg_list_lru_destroy(&s->s_dentry_lru);
+	memcg_list_lru_destroy(&s->s_inode_lru);
 #ifdef CONFIG_SMP
 	free_percpu(s->s_files);
 #endif
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3f40547..f007a37 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1328,8 +1328,8 @@ struct super_block {
 	 * Keep the lru lists last in the structure so they always sit on their
 	 * own individual cachelines.
 	 */
-	struct list_lru		s_dentry_lru ____cacheline_aligned_in_smp;
-	struct list_lru		s_inode_lru ____cacheline_aligned_in_smp;
+	struct memcg_list_lru s_dentry_lru ____cacheline_aligned_in_smp;
+	struct memcg_list_lru s_inode_lru ____cacheline_aligned_in_smp;
 };
 
 extern struct timespec current_fs_time(struct super_block *sb);
-- 
1.7.10.4

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[PATCH v11 12/15] memcg: allow kmem limit to be resized down

[Vladimir Davydov]

From: Glauber Costa <glommer@openvz.org>

The userspace memory limit can be freely resized down. Upon attempt,
reclaim will be called to flush the pages away until we either reach the
limit we want or give up.

It wasn't possible so far with the kmem limit, since we had no way to
shrink the kmem buffers other than using the big hammer of shrink_slab,
that effectively frees data around the whole system.

The situation flips now that we have a per-memcg shrinker
infrastructure. We will proceed analogously to our user memory
counterpart and try to shrink our buffers until we either reach the
limit we want or give up.

Signed-off-by: Glauber Costa <glommer@openvz.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 mm/memcontrol.c |   43 ++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 38 insertions(+), 5 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 03178d0..7bf4dc7 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5574,10 +5574,39 @@ static ssize_t mem_cgroup_read(struct cgroup_subsys_state *css,
 	return simple_read_from_buffer(buf, nbytes, ppos, str, len);
 }
 
+#ifdef CONFIG_MEMCG_KMEM
+/*
+ * This is slightly different than res or memsw reclaim.  We already have
+ * vmscan behind us to drive the reclaim, so we can basically keep trying until
+ * all buffers that can be flushed are flushed. We have a very clear signal
+ * about it in the form of the return value of try_to_free_mem_cgroup_kmem.
+ */
+static int mem_cgroup_resize_kmem_limit(struct mem_cgroup *memcg,
+					unsigned long long val)
+{
+	int ret = -EBUSY;
+
+	for (;;) {
+		if (signal_pending(current)) {
+			ret = -EINTR;
+			break;
+		}
+
+		ret = res_counter_set_limit(&memcg->kmem, val);
+		if (!ret)
+			break;
+
+		/* Can't free anything, pointless to continue */
+		if (!try_to_free_mem_cgroup_kmem(memcg, GFP_KERNEL))
+			break;
+	}
+
+	return ret;
+}
+
 static int memcg_update_kmem_limit(struct cgroup_subsys_state *css, u64 val)
 {
 	int ret = -EINVAL;
-#ifdef CONFIG_MEMCG_KMEM
 	struct mem_cgroup *memcg = mem_cgroup_from_css(css);
 	/*
 	 * For simplicity, we won't allow this to be disabled.  It also can't
@@ -5612,16 +5641,15 @@ static int memcg_update_kmem_limit(struct cgroup_subsys_state *css, u64 val)
 		 * starts accounting before all call sites are patched
 		 */
 		memcg_kmem_set_active(memcg);
-	} else
-		ret = res_counter_set_limit(&memcg->kmem, val);
+	} else {
+		ret = mem_cgroup_resize_kmem_limit(memcg, val);
+	}
 out:
 	mutex_unlock(&set_limit_mutex);
 	mutex_unlock(&memcg_create_mutex);
-#endif
 	return ret;
 }
 
-#ifdef CONFIG_MEMCG_KMEM
 static int memcg_propagate_kmem(struct mem_cgroup *memcg)
 {
 	int ret = 0;
@@ -5658,6 +5686,11 @@ static int memcg_propagate_kmem(struct mem_cgroup *memcg)
 out:
 	return ret;
 }
+#else
+static int memcg_update_kmem_limit(struct cgroup *cont, u64 val)
+{
+	return -EINVAL;
+}
 #endif /* CONFIG_MEMCG_KMEM */
 
 /*
-- 
1.7.10.4

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[PATCH v11 13/15] vmpressure: in-kernel notifications

[Vladimir Davydov]

From: Glauber Costa <glommer@openvz.org>

During the past weeks, it became clear to us that the shrinker interface
we have right now works very well for some particular types of users,
but not that well for others. The later are usually people interested in
one-shot notifications, that were forced to adapt themselves to the
count+scan behavior of shrinkers. To do so, they had no choice than to
greatly abuse the shrinker interface producing little monsters all over.

During LSF/MM, one of the proposals that popped out during our session
was to reuse Anton Voronstsov's vmpressure for this. They are designed
for userspace consumption, but also provide a well-stablished,
cgroup-aware entry point for notifications.

This patch extends that to also support in-kernel users. Events that
should be generated for in-kernel consumption will be marked as such,
and for those, we will call a registered function instead of triggering
an eventfd notification.

Please note that due to my lack of understanding of each shrinker user,
I will stay away from converting the actual users, you are all welcome
to do so.

Signed-off-by: Glauber Costa <glommer@openvz.org>
Acked-by: Anton Vorontsov <anton@enomsg.org>
Acked-by: Pekka Enberg <penberg@kernel.org>
Reviewed-by: Greg Thelen <gthelen@google.com>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
---
 include/linux/vmpressure.h |    5 +++++
 mm/vmpressure.c            |   53 +++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 55 insertions(+), 3 deletions(-)

diff --git a/include/linux/vmpressure.h b/include/linux/vmpressure.h
index 3f3788d..9102e53 100644
--- a/include/linux/vmpressure.h
+++ b/include/linux/vmpressure.h
@@ -19,6 +19,9 @@ struct vmpressure {
 	/* Have to grab the lock on events traversal or modifications. */
 	struct mutex events_lock;
 
+	/* False if only kernel users want to be notified, true otherwise. */
+	bool notify_userspace;
+
 	struct work_struct work;
 };
 
@@ -38,6 +41,8 @@ extern int vmpressure_register_event(struct cgroup_subsys_state *css,
 				     struct cftype *cft,
 				     struct eventfd_ctx *eventfd,
 				     const char *args);
+extern int vmpressure_register_kernel_event(struct cgroup_subsys_state *css,
+					    void (*fn)(void));
 extern void vmpressure_unregister_event(struct cgroup_subsys_state *css,
 					struct cftype *cft,
 					struct eventfd_ctx *eventfd);
diff --git a/mm/vmpressure.c b/mm/vmpressure.c
index e0f6283..730e7c1 100644
--- a/mm/vmpressure.c
+++ b/mm/vmpressure.c
@@ -130,8 +130,12 @@ static enum vmpressure_levels vmpressure_calc_level(unsigned long scanned,
 }
 
 struct vmpressure_event {
-	struct eventfd_ctx *efd;
+	union {
+		struct eventfd_ctx *efd;
+		void (*fn)(void);
+	};
 	enum vmpressure_levels level;
+	bool kernel_event;
 	struct list_head node;
 };
 
@@ -147,12 +151,15 @@ static bool vmpressure_event(struct vmpressure *vmpr,
 	mutex_lock(&vmpr->events_lock);
 
 	list_for_each_entry(ev, &vmpr->events, node) {
-		if (level >= ev->level) {
+		if (ev->kernel_event) {
+			ev->fn();
+		} else if (vmpr->notify_userspace && level >= ev->level) {
 			eventfd_signal(ev->efd, 1);
 			signalled = true;
 		}
 	}
 
+	vmpr->notify_userspace = false;
 	mutex_unlock(&vmpr->events_lock);
 
 	return signalled;
@@ -222,7 +229,7 @@ void vmpressure(gfp_t gfp, struct mem_cgroup *memcg,
 	 * we account it too.
 	 */
 	if (!(gfp & (__GFP_HIGHMEM | __GFP_MOVABLE | __GFP_IO | __GFP_FS)))
-		return;
+		goto schedule;
 
 	/*
 	 * If we got here with no pages scanned, then that is an indicator
@@ -239,8 +246,15 @@ void vmpressure(gfp_t gfp, struct mem_cgroup *memcg,
 	vmpr->scanned += scanned;
 	vmpr->reclaimed += reclaimed;
 	scanned = vmpr->scanned;
+	/*
+	 * If we didn't reach this point, only kernel events will be triggered.
+	 * It is the job of the worker thread to clean this up once the
+	 * notifications are all delivered.
+	 */
+	vmpr->notify_userspace = true;
 	spin_unlock(&vmpr->sr_lock);
 
+schedule:
 	if (scanned < vmpressure_win)
 		return;
 	schedule_work(&vmpr->work);
@@ -324,6 +338,39 @@ int vmpressure_register_event(struct cgroup_subsys_state *css,
 }
 
 /**
+ * vmpressure_register_kernel_event() - Register kernel-side notification
+ * @css:	css that is interested in vmpressure notifications
+ * @fn:		function to be called when pressure happens
+ *
+ * This function register in-kernel users interested in receiving notifications
+ * about pressure conditions. Pressure notifications will be triggered at the
+ * same time as userspace notifications (with no particular ordering relative
+ * to it).
+ *
+ * Pressure notifications are a alternative method to shrinkers and will serve
+ * well users that are interested in a one-shot notification, with a
+ * well-defined cgroup aware interface.
+ */
+int vmpressure_register_kernel_event(struct cgroup_subsys_state *css,
+				      void (*fn)(void))
+{
+	struct vmpressure *vmpr = css_to_vmpressure(css);
+	struct vmpressure_event *ev;
+
+	ev = kzalloc(sizeof(*ev), GFP_KERNEL);
+	if (!ev)
+		return -ENOMEM;
+
+	ev->kernel_event = true;
+	ev->fn = fn;
+
+	mutex_lock(&vmpr->events_lock);
+	list_add(&ev->node, &vmpr->events);
+	mutex_unlock(&vmpr->events_lock);
+	return 0;
+}
+
+/**
  * vmpressure_unregister_event() - Unbind eventfd from vmpressure
  * @css:	css handle
  * @cft:	cgroup control files handle
-- 
1.7.10.4

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[PATCH v11 14/15] memcg: reap dead memcgs upon global memory pressure

[Vladimir Davydov]

From: Glauber Costa <glommer@openvz.org>

When we delete kmem-enabled memcgs, they can still be zombieing
around for a while. The reason is that the objects may still be alive,
and we won't be able to delete them at destruction time.

The only entry point for that, though, are the shrinkers. The
shrinker interface, however, is not exactly tailored to our needs. It
could be a little bit better by using the API Dave Chinner proposed, but
it is still not ideal since we aren't really a count-and-scan event, but
more a one-off flush-all-you-can event that would have to abuse that
somehow.

Signed-off-by: Glauber Costa <glommer@openvz.org>
Cc: Anton Vorontsov <anton@enomsg.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
---
 mm/memcontrol.c |   80 ++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 77 insertions(+), 3 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 7bf4dc7..628ea0d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -285,8 +285,16 @@ struct mem_cgroup {
 	/* thresholds for mem+swap usage. RCU-protected */
 	struct mem_cgroup_thresholds memsw_thresholds;
 
-	/* For oom notifier event fd */
-	struct list_head oom_notify;
+	union {
+		/* For oom notifier event fd */
+		struct list_head oom_notify;
+		/*
+		 * we can only trigger an oom event if the memcg is alive.
+		 * so we will reuse this field to hook the memcg in the list
+		 * of dead memcgs.
+		 */
+		struct list_head dead;
+	};
 
 	/*
 	 * Should we move charges of a task when a task is moved into this
@@ -336,6 +344,29 @@ struct mem_cgroup {
 	/* WARNING: nodeinfo must be the last member here */
 };
 
+#if defined(CONFIG_MEMCG_KMEM) || defined(CONFIG_MEMCG_SWAP)
+static LIST_HEAD(dangling_memcgs);
+static DEFINE_MUTEX(dangling_memcgs_mutex);
+
+static inline void memcg_dangling_del(struct mem_cgroup *memcg)
+{
+	mutex_lock(&dangling_memcgs_mutex);
+	list_del(&memcg->dead);
+	mutex_unlock(&dangling_memcgs_mutex);
+}
+
+static inline void memcg_dangling_add(struct mem_cgroup *memcg)
+{
+	INIT_LIST_HEAD(&memcg->dead);
+	mutex_lock(&dangling_memcgs_mutex);
+	list_add(&memcg->dead, &dangling_memcgs);
+	mutex_unlock(&dangling_memcgs_mutex);
+}
+#else
+static inline void memcg_dangling_free(struct mem_cgroup *memcg) {}
+static inline void memcg_dangling_add(struct mem_cgroup *memcg) {}
+#endif
+
 static size_t memcg_size(void)
 {
 	return sizeof(struct mem_cgroup) +
@@ -6352,6 +6383,41 @@ static int mem_cgroup_oom_control_write(struct cgroup_subsys_state *css,
 }
 
 #ifdef CONFIG_MEMCG_KMEM
+static void memcg_vmpressure_shrink_dead(void)
+{
+	struct memcg_cache_params *params, *tmp;
+	struct kmem_cache *cachep;
+	struct mem_cgroup *memcg;
+
+	mutex_lock(&dangling_memcgs_mutex);
+	list_for_each_entry(memcg, &dangling_memcgs, dead) {
+		mutex_lock(&memcg->slab_caches_mutex);
+		/* The element may go away as an indirect result of shrink */
+		list_for_each_entry_safe(params, tmp,
+					 &memcg->memcg_slab_caches, list) {
+			cachep = memcg_params_to_cache(params);
+			/*
+			 * the cpu_hotplug lock is taken in kmem_cache_create
+			 * outside the slab_caches_mutex manipulation. It will
+			 * be taken by kmem_cache_shrink to flush the cache.
+			 * So we need to drop the lock. It is all right because
+			 * the lock only protects elements moving in and out the
+			 * list.
+			 */
+			mutex_unlock(&memcg->slab_caches_mutex);
+			kmem_cache_shrink(cachep);
+			mutex_lock(&memcg->slab_caches_mutex);
+		}
+		mutex_unlock(&memcg->slab_caches_mutex);
+	}
+	mutex_unlock(&dangling_memcgs_mutex);
+}
+
+static void memcg_register_kmem_events(struct cgroup_subsys_state *css)
+{
+	vmpressure_register_kernel_event(css, memcg_vmpressure_shrink_dead);
+}
+
 static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
 {
 	int ret;
@@ -6409,6 +6475,10 @@ static void kmem_cgroup_css_offline(struct mem_cgroup *memcg)
 		css_put(&memcg->css);
 }
 #else
+static inline void memcg_register_kmem_events(struct cgroup *cont)
+{
+}
+
 static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
 {
 	return 0;
@@ -6745,8 +6815,10 @@ mem_cgroup_css_online(struct cgroup_subsys_state *css)
 	struct mem_cgroup *parent = mem_cgroup_from_css(css_parent(css));
 	int error = 0;
 
-	if (!parent)
+	if (!parent) {
+		memcg_register_kmem_events(css);
 		return 0;
+	}
 
 	mutex_lock(&memcg_create_mutex);
 
@@ -6808,6 +6880,7 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
 	mem_cgroup_invalidate_reclaim_iterators(memcg);
 	mem_cgroup_reparent_charges(memcg);
 	mem_cgroup_destroy_all_caches(memcg);
+	memcg_dangling_add(memcg);
 	vmpressure_cleanup(&memcg->vmpressure);
 }
 
@@ -6816,6 +6889,7 @@ static void mem_cgroup_css_free(struct cgroup_subsys_state *css)
 	struct mem_cgroup *memcg = mem_cgroup_from_css(css);
 
 	memcg_destroy_kmem(memcg);
+	memcg_dangling_del(memcg);
 	__mem_cgroup_free(memcg);
 }
 
-- 
1.7.10.4

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[PATCH v11 15/15] memcg: flush memcg items upon memcg destruction

[Vladimir Davydov]

From: Glauber Costa <glommer@openvz.org>

When a memcg is destroyed, it won't be imediately released until all
objects are gone. This means that if a memcg is restarted with the very
same workload - a very common case, the objects already cached won't be
billed to the new memcg. This is mostly undesirable since a container
can exploit this by restarting itself every time it reaches its limit,
and then coming up again with a fresh new limit.

Since now we have targeted reclaim, I sustain that we should assume that
a memcg that is destroyed should be flushed away. It makes perfect sense
if we assume that a memcg that goes away most likely indicates an
isolated workload that is terminated.

Signed-off-by: Glauber Costa <glommer@openvz.org>
Cc: Mel Gorman <mgorman@suse.de>
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>
---
 mm/memcontrol.c |   17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 628ea0d..6dadbbe 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6441,12 +6441,29 @@ static void memcg_destroy_kmem(struct mem_cgroup *memcg)
 
 static void kmem_cgroup_css_offline(struct mem_cgroup *memcg)
 {
+	int ret;
 	if (!memcg_kmem_is_active(memcg))
 		return;
 
 	cancel_work_sync(&memcg->kmemcg_shrink_work);
 
 	/*
+	 * When a memcg is destroyed, it won't be imediately released until all
+	 * objects are gone. This means that if a memcg is restarted with the
+	 * very same workload - a very common case, the objects already cached
+	 * won't be billed to the new memcg. This is mostly undesirable since a
+	 * container can exploit this by restarting itself every time it
+	 * reaches its limit, and then coming up again with a fresh new limit.
+	 *
+	 * Therefore a memcg that is destroyed should be flushed away. It makes
+	 * perfect sense if we assume that a memcg that goes away indicates an
+	 * isolated workload that is terminated.
+	 */
+	do {
+		ret = try_to_free_mem_cgroup_kmem(memcg, GFP_KERNEL);
+	} while (ret);
+
+	/*
 	 * kmem charges can outlive the cgroup. In the case of slab
 	 * pages, for instance, a page contain objects from various
 	 * processes. As we prevent from taking a reference for every
-- 
1.7.10.4

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Re: [Devel] [PATCH v11 00/15] kmemcg shrinkers

[Vladimir Davydov]

I've run kernbench in a first-level memory cgroup to prove there is no 
performance degradation due to the series, and here are the results.

HW: 2 socket x 6 core x 2 HT (2 NUMA nodes, 24 logical CPUs in total), 
24 GB RAM (12+12)
Test case: time make -j48 vmlinux
Legend:
   base - 3.12.0-rc6
   patched - 3.12.0-rc6 + patchset

1) To compute the overhead of making s_inode_lru and s_dentry_lru lists 
per-memcg, the test was run in a first-level memory cgroup with the 
following parameters:

memory.limit_in_bytes=-1
memory.kmem_limit_in_bytes=2147483648

[the kmem limit is set in order to activate kmem accounting in memcg, 
but since it is high enough to accommodate all kernel objects created 
during the test, the reclaimer is never called]

* base
Elapsed time: 314.7 +- 0.9 sec
User time: 5103.5 +- 11.0 sec
System time: 540.7 +- 1.0 sec
CPU usage: 1793.2 +- 6.1 %

* patched
Elapsed time: 313.6 +- 1.4 sec
User time: 5096.4 +- 10.8 sec
System time: 538.9 +- 1.6 sec
CPU usage: 1796.2 +- 9.4 %

 From the results above, one may conclude there is practically no 
overhead of making the inode and dentry lists per-memcg.

2) To compute the impact of the series on the memory reclaimer, the test 
was run in a first-level cgroup with the following parameters:

memory.limit_in_bytes=2147483648
memory.kmem_limit_in_bytes=2147483648

[48 compilation threads competing for 2GB of RAM create memory pressure 
high enough to trigger memory reclaimer]

* base
Elapsed time: 705.2 +- 104.2 sec
User time: 4489.1 +- 48.2 sec
System time: 494.4 +- 4.9 sec
CPU usage: 724.0 +- 122.3 %

* patched
Elapsed time: 659.6 +- 98.4 sec (-45.6 sec / -6.4 % vs base)
User time: 4506.5 +- 52.7 sec (+17.4 sec / +0.4 % vs base)
System time: 494.7 +- 7.8 sec (+0.3 sec / +0.0 % vs base)
CPU usage: 774.7 +- 115.6 % (+50.7 % / +7.0 % bs base)

It seems that shrinking icache/dcache along with page caches resulted in 
slight improvement in CPU utilization and overall performance (elapsed 
time). This is predictable, because the kernel w/o the patchset applied 
in fact does not shrink icache/dcache at all under memcg pressure 
keeping them in memory during all the test run. In total, this can 
result in up to 300 MB of memory wasted. In contrary, the patched kernel 
tries to reclaim kernel objects along with user pages freeing space for 
the effective working set.

Thus, I guess the overhead introduced by the series is reasonable.

Thanks.

On 10/24/2013 04:04 PM, Vladimir Davydov wrote:
> This patchset implements targeted shrinking for memcg when kmem limits are
> present. So far, we've been accounting kernel objects but failing allocations
> when short of memory. This is because our only option would be to call the
> global shrinker, depleting objects from all caches and breaking isolation.
>
> The main idea is to associate per-memcg lists with each of the LRUs. The main
> LRU still provides a single entry point and when adding or removing an element
> from the LRU, we use the page information to figure out which memcg it belongs
> to and relay it to the right list.
>
> The bulk of the code is written by Glauber Costa. The only change I introduced
> myself in this iteration is reworking per-memcg LRU lists. Instead of extending
> the existing list_lru structure, which seems to be neat as is, I introduced a
> new one, memcg_list_lru, which aggregates list_lru objects for each kmem-active
> memcg and keeps them uptodate as memcgs are created/destroyed. I hope this
> simplified call paths and made the code easier to read.
>
> The patchset is based on top of Linux 3.12-rc6.
>
> Any comments and proposals are appreciated.
>
> == Known issues ==
>
>   * In case kmem limit is less than sum mem limit, reaching memcg kmem limit
>     will result in an attempt to shrink all memcg slabs (see
>     try_to_free_mem_cgroup_kmem()). Although this is better than simply failing
>     allocation as it works now, it is still to be improved.
>
>   * Since FS shrinkers can't be executed on __GFP_FS allocations, such
>     allocations will fail if memcg kmem limit is less than sum mem limit and the
>     memcg kmem usage is close to its limit. Glauber proposed to schedule a
>     worker which would shrink kmem in the background on such allocations.
>     However, this approach does not eliminate failures completely, it just makes
>     them rarer. I'm thinking on implementing soft limits for memcg kmem so that
>     striking the soft limit will trigger the reclaimer, but won't fail the
>     allocation. I would appreciate any other proposals on how this can be fixed.
>
>   * Only dcache and icache are reclaimed on memcg pressure. Other FS objects are
>     left for global pressure only. However, it should not be a serious problem
>     to make them reclaimable too by passing on memcg to the FS-layer and letting
>     each FS decide if its internal objects are shrinkable on memcg pressure.
>
> == Changes from v10 ==
>
>   * Rework per-memcg list_lru infrastructure.
>
> Previous iteration (with full changelog) can be found here:
>
> http://www.spinics.net/lists/linux-fsdevel/msg66632.html
>
> Glauber Costa (12):
>    memcg: make cache index determination more robust
>    memcg: consolidate callers of memcg_cache_id
>    vmscan: also shrink slab in memcg pressure
>    memcg: move initialization to memcg creation
>    memcg: move stop and resume accounting functions
>    memcg: per-memcg kmem shrinking
>    memcg: scan cache objects hierarchically
>    vmscan: take at least one pass with shrinkers
>    memcg: allow kmem limit to be resized down
>    vmpressure: in-kernel notifications
>    memcg: reap dead memcgs upon global memory pressure
>    memcg: flush memcg items upon memcg destruction
>
> Vladimir Davydov (3):
>    memcg,list_lru: add per-memcg LRU list infrastructure
>    memcg,list_lru: add function walking over all lists of a per-memcg
>      LRU
>    super: make icache, dcache shrinkers memcg-aware
>
>   fs/dcache.c                |   25 +-
>   fs/inode.c                 |   16 +-
>   fs/internal.h              |    9 +-
>   fs/super.c                 |   47 +--
>   include/linux/fs.h         |    4 +-
>   include/linux/list_lru.h   |   77 +++++
>   include/linux/memcontrol.h |   23 ++
>   include/linux/shrinker.h   |    6 +-
>   include/linux/swap.h       |    2 +
>   include/linux/vmpressure.h |    5 +
>   mm/memcontrol.c            |  704 +++++++++++++++++++++++++++++++++++++++-----
>   mm/vmpressure.c            |   53 +++-
>   mm/vmscan.c                |  178 +++++++++--
>   13 files changed, 1014 insertions(+), 135 deletions(-)
>

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[PATCH v11 00/15] kmemcg shrinkers

[Vladimir Davydov]

This patchset implements targeted shrinking for memcg when kmem limits are
present. So far, we've been accounting kernel objects but failing allocations
when short of memory. This is because our only option would be to call the
global shrinker, depleting objects from all caches and breaking isolation.

The main idea is to associate per-memcg lists with each of the LRUs. The main
LRU still provides a single entry point and when adding or removing an element
from the LRU, we use the page information to figure out which memcg it belongs
to and relay it to the right list.

The bulk of the code is written by Glauber Costa. The only change I introduced
myself in this iteration is reworking per-memcg LRU lists. Instead of extending
the existing list_lru structure, which seems to be neat as is, I introduced a
new one, memcg_list_lru, which aggregates list_lru objects for each kmem-active
memcg and keeps them uptodate as memcgs are created/destroyed. I hope this
simplified call paths and made the code easier to read.

The patchset is based on top of Linux 3.13-rc1.

Any comments and proposals are appreciated.

== Known issues ==

 * In case kmem limit is less than sum mem limit, reaching memcg kmem limit
   will result in an attempt to shrink all memcg slabs (see
   try_to_free_mem_cgroup_kmem()). Although this is better than simply failing
   allocation as it works now, it is still to be improved.

 * Since FS shrinkers can't be executed on __GFP_FS allocations, such
   allocations will fail if memcg kmem limit is less than sum mem limit and the
   memcg kmem usage is close to its limit. Glauber proposed to schedule a
   worker which would shrink kmem in the background on such allocations.
   However, this approach does not eliminate failures completely, it just makes
   them rarer. I'm thinking on implementing soft limits for memcg kmem so that
   striking the soft limit will trigger the reclaimer, but won't fail the
   allocation. I would appreciate any other proposals on how this can be fixed.

 * Only dcache and icache are reclaimed on memcg pressure. Other FS objects are
   left for global pressure only. However, it should not be a serious problem
   to make them reclaimable too by passing on memcg to the FS-layer and letting
   each FS decide if its internal objects are shrinkable on memcg pressure.

== Changes from v10 ==

 * Rework per-memcg list_lru infrastructure.

Previous iteration (with full changelog) can be found here:

http://www.spinics.net/lists/linux-fsdevel/msg66632.html

Glauber Costa (12):
  memcg: make cache index determination more robust
  memcg: consolidate callers of memcg_cache_id
  vmscan: also shrink slab in memcg pressure
  memcg: move initialization to memcg creation
  memcg: move stop and resume accounting functions
  memcg: per-memcg kmem shrinking
  memcg: scan cache objects hierarchically
  vmscan: take at least one pass with shrinkers
  memcg: allow kmem limit to be resized down
  vmpressure: in-kernel notifications
  memcg: reap dead memcgs upon global memory pressure
  memcg: flush memcg items upon memcg destruction

Vladimir Davydov (3):
  memcg,list_lru: add per-memcg LRU list infrastructure
  memcg,list_lru: add function walking over all lists of a per-memcg
    LRU
  super: make icache, dcache shrinkers memcg-aware

 fs/dcache.c                |   25 +-
 fs/inode.c                 |   16 +-
 fs/internal.h              |    9 +-
 fs/super.c                 |   45 +--
 include/linux/fs.h         |    4 +-
 include/linux/list_lru.h   |   77 +++++
 include/linux/memcontrol.h |   23 ++
 include/linux/shrinker.h   |    6 +-
 include/linux/swap.h       |    2 +
 include/linux/vmpressure.h |    5 +
 mm/memcontrol.c            |  709 +++++++++++++++++++++++++++++++++++++++-----
 mm/vmpressure.c            |   53 +++-
 mm/vmscan.c                |  178 +++++++++--
 13 files changed, 1018 insertions(+), 134 deletions(-)

-- 
1.7.10.4

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Re: [PATCH v11 00/15] kmemcg shrinkers

[Johannes Weiner]

I ran out of steam reviewing these because there were too many things
that should be changed in the first couple patches.

I realize this is frustrating to see these type of complaints in v11
of a patch series, but the review bandwidth was simply exceeded back
when Glauber submitted this along with the kmem accounting patches.  A
lot of the kmemcg commits themselves don't even have review tags or
acks, but it all got merged anyway, and the author has moved on to
different projects...

Too much stuff slips past the only two people that have more than one
usecase on their agenda and are willing to maintain this code base -
which is in desparate need of rework and pushback against even more
drive-by feature dumps.  I have repeatedly asked to split the memcg
tree out of the memory tree to better deal with the vastly different
developmental stages of memcg and the rest of the mm code, to no
avail.  So I don't know what to do anymore, but this is not working.

Thoughts?

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Re: [PATCH v11 00/15] kmemcg shrinkers

[Vladimir Davydov]

Hi,

Thank you for the review. I agree with all your comments and I'll resend 
the fixed version soon.

If anyone still has something to say about the patchset, I'd be glad to 
hear from them.

On 11/25/2013 09:41 PM, Johannes Weiner wrote:
> I ran out of steam reviewing these because there were too many things
> that should be changed in the first couple patches.
>
> I realize this is frustrating to see these type of complaints in v11
> of a patch series, but the review bandwidth was simply exceeded back
> when Glauber submitted this along with the kmem accounting patches.  A
> lot of the kmemcg commits themselves don't even have review tags or
> acks, but it all got merged anyway, and the author has moved on to
> different projects...
>
> Too much stuff slips past the only two people that have more than one
> usecase on their agenda and are willing to maintain this code base -
> which is in desparate need of rework and pushback against even more
> drive-by feature dumps.  I have repeatedly asked to split the memcg
> tree out of the memory tree to better deal with the vastly different
> developmental stages of memcg and the rest of the mm code, to no
> avail.  So I don't know what to do anymore, but this is not working.
>
> Thoughts?

That's a pity, because w/o this patchset kmemcg is in fact useless. 
Perhaps, it's worth trying to split it? (not sure if it'll help much 
though since first 11 patches are rather essential :-( )

Thanks.

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Re: [Devel] [PATCH v11 00/15] kmemcg shrinkers

[Vladimir Davydov]

On 11/26/2013 10:47 AM, Vladimir Davydov wrote:
> Hi,
>
> Thank you for the review. I agree with all your comments and I'll 
> resend the fixed version soon.
>
> If anyone still has something to say about the patchset, I'd be glad 
> to hear from them.
>
> On 11/25/2013 09:41 PM, Johannes Weiner wrote:
>> I ran out of steam reviewing these because there were too many things
>> that should be changed in the first couple patches.
>>
>> I realize this is frustrating to see these type of complaints in v11
>> of a patch series, but the review bandwidth was simply exceeded back
>> when Glauber submitted this along with the kmem accounting patches.  A
>> lot of the kmemcg commits themselves don't even have review tags or
>> acks, but it all got merged anyway, and the author has moved on to
>> different projects...
>>
>> Too much stuff slips past the only two people that have more than one
>> usecase on their agenda and are willing to maintain this code base -
>> which is in desparate need of rework and pushback against even more
>> drive-by feature dumps.  I have repeatedly asked to split the memcg
>> tree out of the memory tree to better deal with the vastly different
>> developmental stages of memcg and the rest of the mm code, to no
>> avail.  So I don't know what to do anymore, but this is not working.
>>
>> Thoughts?
>
> That's a pity, because w/o this patchset kmemcg is in fact useless. 
> Perhaps, it's worth trying to split it? (not sure if it'll help much 
> though since first 11 patches are rather essential :-( )

What do you think about splitting this set into two main series as follows:

1) Prepare vmscan to kmemcg-aware shrinkers; would include patches 1-7 
of this set.
2) Make fs shrinkers memcg-aware; would include patches 9-11 of this set

and leave other patches, which are rather for optimization/extending 
functionality, for future?

Thanks.

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Re: [Devel] [PATCH v11 00/15] kmemcg shrinkers

[Andrew Morton]

On Tue, 26 Nov 2013 16:55:43 +0400 Vladimir Davydov <vdavydov@parallels.com> wrote:

> What do you think about splitting this set into two main series as follows:
> 
> 1) Prepare vmscan to kmemcg-aware shrinkers; would include patches 1-7 
> of this set.
> 2) Make fs shrinkers memcg-aware; would include patches 9-11 of this set

Please just resend everything.

> and leave other patches, which are rather for optimization/extending 
> functionality, for future?

It will be helpful to describe such splitting opportunities in the
[0/n] changelog.

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