[PATCH 3/3] mm: workingset: cgroup-aware

[Johannes Weiner <hannes@cmpxchg.org>]

TODO:
- cgroup-aware shadow node reclaim

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
 include/linux/memcontrol.h | 39 ++++++++++++++++++++++++++++++
 include/linux/mmzone.h     | 11 ++++-----
 include/linux/swap.h       |  1 +
 mm/memcontrol.c            | 25 --------------------
 mm/vmscan.c                | 18 +++++++-------
 mm/workingset.c            | 59 +++++++++++++++++++++++++++++++++++++---------
 6 files changed, 102 insertions(+), 51 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 792c8981e633..705aba54a50d 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -89,6 +89,10 @@ enum mem_cgroup_events_target {
 };
 
 #ifdef CONFIG_MEMCG
+
+#define MEM_CGROUP_ID_SHIFT	16
+#define MEM_CGROUP_ID_MAX	USHRT_MAX
+
 struct mem_cgroup_stat_cpu {
 	long count[MEMCG_NR_STAT];
 	unsigned long events[MEMCG_NR_EVENTS];
@@ -312,6 +316,25 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *,
 				   struct mem_cgroup_reclaim_cookie *);
 void mem_cgroup_iter_break(struct mem_cgroup *, struct mem_cgroup *);
 
+static inline unsigned short mem_cgroup_id(struct mem_cgroup *memcg)
+{
+	return memcg->css.id;
+}
+
+/**
+ * mem_cgroup_from_id - look up a memcg from an id
+ * @id: the id to look up
+ *
+ * Caller must hold rcu_read_lock() and use css_tryget() as necessary.
+ */
+static inline struct mem_cgroup *mem_cgroup_from_id(unsigned short id)
+{
+	struct cgroup_subsys_state *css;
+
+	css = css_from_id(id, &memory_cgrp_subsys);
+	return mem_cgroup_from_css(css);
+}
+
 /**
  * parent_mem_cgroup - find the accounting parent of a memcg
  * @memcg: memcg whose parent to find
@@ -496,6 +519,10 @@ void mem_cgroup_split_huge_fixup(struct page *head);
 #endif
 
 #else /* CONFIG_MEMCG */
+
+#define MEM_CGROUP_ID_SHIFT	0
+#define MEM_CGROUP_ID_MAX	0
+
 struct mem_cgroup;
 
 static inline void mem_cgroup_events(struct mem_cgroup *memcg,
@@ -580,6 +607,18 @@ static inline void mem_cgroup_iter_break(struct mem_cgroup *root,
 {
 }
 
+static inline unsigned short mem_cgroup_id(struct mem_cgroup *memcg)
+{
+	return 0;
+}
+
+static inline struct mem_cgroup *mem_cgroup_from_id(unsigned short id)
+{
+	WARN_ON_ONCE(id);
+	/* XXX: This should always return root_mem_cgroup */
+	return NULL;
+}
+
 static inline bool mem_cgroup_disabled(void)
 {
 	return true;
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 33bb1b19273e..a7d8eeb6658a 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -209,10 +209,12 @@ struct zone_reclaim_stat {
 };
 
 struct lruvec {
-	struct list_head lists[NR_LRU_LISTS];
-	struct zone_reclaim_stat reclaim_stat;
+	struct list_head		lists[NR_LRU_LISTS];
+	struct zone_reclaim_stat	reclaim_stat;
+	/* Evictions & activations on the inactive file list */
+	atomic_long_t			inactive_age;
 #ifdef CONFIG_MEMCG
-	struct zone *zone;
+	struct zone			*zone;
 #endif
 };
 
@@ -487,9 +489,6 @@ struct zone {
 	spinlock_t		lru_lock;
 	struct lruvec		lruvec;
 
-	/* Evictions & activations on the inactive file list */
-	atomic_long_t		inactive_age;
-
 	/*
 	 * When free pages are below this point, additional steps are taken
 	 * when reading the number of free pages to avoid per-cpu counter
diff --git a/include/linux/swap.h b/include/linux/swap.h
index b14a2bb33514..1cf3065c143b 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -317,6 +317,7 @@ extern void lru_cache_add_active_or_unevictable(struct page *page,
 
 /* linux/mm/vmscan.c */
 extern unsigned long zone_reclaimable_pages(struct zone *zone);
+extern unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru);
 extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
 					gfp_t gfp_mask, nodemask_t *mask);
 extern int __isolate_lru_page(struct page *page, isolate_mode_t mode);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index d06cae2de783..4ea79f225fe8 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -268,31 +268,6 @@ static inline bool mem_cgroup_is_root(struct mem_cgroup *memcg)
 	return (memcg == root_mem_cgroup);
 }
 
-/*
- * We restrict the id in the range of [1, 65535], so it can fit into
- * an unsigned short.
- */
-#define MEM_CGROUP_ID_MAX	USHRT_MAX
-
-static inline unsigned short mem_cgroup_id(struct mem_cgroup *memcg)
-{
-	return memcg->css.id;
-}
-
-/*
- * A helper function to get mem_cgroup from ID. must be called under
- * rcu_read_lock().  The caller is responsible for calling
- * css_tryget_online() if the mem_cgroup is used for charging. (dropping
- * refcnt from swap can be called against removed memcg.)
- */
-static inline struct mem_cgroup *mem_cgroup_from_id(unsigned short id)
-{
-	struct cgroup_subsys_state *css;
-
-	css = css_from_id(id, &memory_cgrp_subsys);
-	return mem_cgroup_from_css(css);
-}
-
 #ifndef CONFIG_SLOB
 /*
  * This will be the memcg's index in each cache's ->memcg_params.memcg_caches.
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 30e0cd7a0ceb..f4ac04c0d35a 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -213,7 +213,7 @@ bool zone_reclaimable(struct zone *zone)
 		zone_reclaimable_pages(zone) * 6;
 }
 
-static unsigned long get_lru_size(struct lruvec *lruvec, enum lru_list lru)
+unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru)
 {
 	if (!mem_cgroup_disabled())
 		return mem_cgroup_get_lru_size(lruvec, lru);
@@ -1931,8 +1931,8 @@ static bool inactive_file_is_low(struct lruvec *lruvec)
 	unsigned long inactive;
 	unsigned long active;
 
-	inactive = get_lru_size(lruvec, LRU_INACTIVE_FILE);
-	active = get_lru_size(lruvec, LRU_ACTIVE_FILE);
+	inactive = lruvec_lru_size(lruvec, LRU_INACTIVE_FILE);
+	active = lruvec_lru_size(lruvec, LRU_ACTIVE_FILE);
 
 	return active > inactive;
 }
@@ -2071,7 +2071,7 @@ static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg,
 	 * system is under heavy pressure.
 	 */
 	if (!inactive_file_is_low(lruvec) &&
-	    get_lru_size(lruvec, LRU_INACTIVE_FILE) >> sc->priority) {
+	    lruvec_lru_size(lruvec, LRU_INACTIVE_FILE) >> sc->priority) {
 		scan_balance = SCAN_FILE;
 		goto out;
 	}
@@ -2097,10 +2097,10 @@ static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg,
 	 * anon in [0], file in [1]
 	 */
 
-	anon  = get_lru_size(lruvec, LRU_ACTIVE_ANON) +
-		get_lru_size(lruvec, LRU_INACTIVE_ANON);
-	file  = get_lru_size(lruvec, LRU_ACTIVE_FILE) +
-		get_lru_size(lruvec, LRU_INACTIVE_FILE);
+	anon  = lruvec_lru_size(lruvec, LRU_ACTIVE_ANON) +
+		lruvec_lru_size(lruvec, LRU_INACTIVE_ANON);
+	file  = lruvec_lru_size(lruvec, LRU_ACTIVE_FILE) +
+		lruvec_lru_size(lruvec, LRU_INACTIVE_FILE);
 
 	spin_lock_irq(&zone->lru_lock);
 	if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
@@ -2138,7 +2138,7 @@ out:
 			unsigned long size;
 			unsigned long scan;
 
-			size = get_lru_size(lruvec, lru);
+			size = lruvec_lru_size(lruvec, lru);
 			scan = size >> sc->priority;
 
 			if (!scan && pass && force_scan)
diff --git a/mm/workingset.c b/mm/workingset.c
index ac6eb7bc1faa..fe69da29bbad 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -152,7 +152,8 @@
  * refault distance will immediately activate the refaulting page.
  */
 
-#define EVICTION_SHIFT (NODES_SHIFT + ZONES_SHIFT +	\
+#define EVICTION_SHIFT (MEM_CGROUP_ID_SHIFT +		\
+			NODES_SHIFT + ZONES_SHIFT +	\
 			RADIX_TREE_EXCEPTIONAL_SHIFT)
 #define EVICTION_MASK (~0UL >> EVICTION_SHIFT)
 
@@ -166,9 +167,10 @@
  */
 static unsigned int bucket_order;
 
-static void *pack_shadow(unsigned long eviction, struct zone *zone)
+static void *pack_shadow(int memcgid, struct zone *zone, unsigned long eviction)
 {
 	eviction >>= bucket_order;
+	eviction = (eviction << MEM_CGROUP_ID_SHIFT) | memcgid;
 	eviction = (eviction << NODES_SHIFT) | zone_to_nid(zone);
 	eviction = (eviction << ZONES_SHIFT) | zone_idx(zone);
 	eviction = (eviction << RADIX_TREE_EXCEPTIONAL_SHIFT);
@@ -176,21 +178,23 @@ static void *pack_shadow(unsigned long eviction, struct zone *zone)
 	return (void *)(eviction | RADIX_TREE_EXCEPTIONAL_ENTRY);
 }
 
-static void unpack_shadow(void *shadow, struct zone **zonep,
+static void unpack_shadow(void *shadow, int *memcgidp, struct zone **zonep,
 			  unsigned long *evictionp)
 {
 	unsigned long entry = (unsigned long)shadow;
-	int zid, nid;
+	int memcgid, nid, zid;
 
 	entry >>= RADIX_TREE_EXCEPTIONAL_SHIFT;
 	zid = entry & ((1UL << ZONES_SHIFT) - 1);
 	entry >>= ZONES_SHIFT;
 	nid = entry & ((1UL << NODES_SHIFT) - 1);
 	entry >>= NODES_SHIFT;
+	memcgid = entry & ((1UL << MEM_CGROUP_ID_SHIFT) - 1);
+	entry >>= MEM_CGROUP_ID_SHIFT;
 
+	*memcgidp = memcgid;
 	*zonep = NODE_DATA(nid)->node_zones + zid;
 	*evictionp = entry << bucket_order;
-
 }
 
 /**
@@ -203,11 +207,20 @@ static void unpack_shadow(void *shadow, struct zone **zonep,
  */
 void *workingset_eviction(struct address_space *mapping, struct page *page)
 {
+	struct mem_cgroup *memcg = page_memcg(page);
 	struct zone *zone = page_zone(page);
+	int memcgid = mem_cgroup_id(memcg);
 	unsigned long eviction;
+	struct lruvec *lruvec;
+
+	/* Page is fully exclusive and pins page->mem_cgroup */
+	VM_BUG_ON_PAGE(PageLRU(page), page);
+	VM_BUG_ON_PAGE(page_count(page), page);
+	VM_BUG_ON_PAGE(!PageLocked(page), page);
 
-	eviction = atomic_long_inc_return(&zone->inactive_age);
-	return pack_shadow(eviction, zone);
+	lruvec = mem_cgroup_zone_lruvec(zone, memcg);
+	eviction = atomic_long_inc_return(&lruvec->inactive_age);
+	return pack_shadow(memcgid, zone, eviction);
 }
 
 /**
@@ -222,13 +235,32 @@ void *workingset_eviction(struct address_space *mapping, struct page *page)
 bool workingset_refault(void *shadow)
 {
 	unsigned long refault_distance;
+	unsigned long active_file;
+	struct mem_cgroup *memcg;
 	unsigned long eviction;
+	struct lruvec *lruvec;
 	unsigned long refault;
 	struct zone *zone;
+	int memcgid;
 
-	unpack_shadow(shadow, &zone, &eviction);
+	unpack_shadow(shadow, &memcgid, &zone, &eviction);
 
-	refault = atomic_long_read(&zone->inactive_age);
+	rcu_read_lock();
+	memcg = mem_cgroup_from_id(memcgid);
+	/*
+	 * Don't count a refault if the remembered memcg has been
+	 * deleted since. XXX: On !CONFIG_MEMCG, this will always
+	 * return NULL; it would be better if the root_mem_cgroup
+	 * existed in all configurations instead.
+	 */
+	if (!mem_cgroup_disabled() && !memcg) {
+		rcu_read_unlock();
+		return false;
+	}
+	lruvec = mem_cgroup_zone_lruvec(zone, memcg);
+	refault = atomic_long_read(&lruvec->inactive_age);
+	active_file = lruvec_lru_size(lruvec, LRU_ACTIVE_FILE);
+	rcu_read_unlock();
 
 	/*
 	 * The unsigned subtraction here gives an accurate distance
@@ -250,7 +282,7 @@ bool workingset_refault(void *shadow)
 
 	inc_zone_state(zone, WORKINGSET_REFAULT);
 
-	if (refault_distance <= zone_page_state(zone, NR_ACTIVE_FILE)) {
+	if (refault_distance <= active_file) {
 		inc_zone_state(zone, WORKINGSET_ACTIVATE);
 		return true;
 	}
@@ -263,7 +295,12 @@ bool workingset_refault(void *shadow)
  */
 void workingset_activation(struct page *page)
 {
-	atomic_long_inc(&page_zone(page)->inactive_age);
+	struct lruvec *lruvec;
+
+	rcu_read_lock();
+	lruvec = mem_cgroup_zone_lruvec(page_zone(page), page_memcg(page));
+	atomic_long_inc(&lruvec->inactive_age);
+	rcu_read_unlock();
 }
 
 /*
-- 
2.7.0

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