[PATCH v11 11/25] list_lru: per-node list infrastructure

[Glauber Costa <glommer-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>]

From: Dave Chinner <dchinner-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>

Now that we have an LRU list API, we can start to enhance the
implementation.  This splits the single LRU list into per-node lists
and locks to enhance scalability. Items are placed on lists
according to the node the memory belongs to. To make scanning the
lists efficient, also track whether the per-node lists have entries
in them in a active nodemask.

Note:
We use a fixed-size array for the node LRU, this struct can be very big
if MAX_NUMNODES is big. If this becomes a problem this is fixable by
turning this into a pointer and dynamically allocating this to
nr_node_ids. This quantity is firwmare-provided, and still would provide
room for all nodes at the cost of a pointer lookup and an extra
allocation. Because that allocation will most likely come from a
different slab cache than the main structure holding this structure, we
may very well fail.

[ glommer: fixed warnings, added note about node lru ]
Signed-off-by: Dave Chinner <dchinner-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Glauber Costa <glommer-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>
Reviewed-by: Greg Thelen <gthelen-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Acked-by: Mel Gorman <mgorman-l3A5Bk7waGM@public.gmane.org>
---
 include/linux/list_lru.h |  23 ++++++--
 mm/list_lru.c            | 146 +++++++++++++++++++++++++++++++++++------------
 2 files changed, 129 insertions(+), 40 deletions(-)

diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
index 1a548b0..f4d4cb6 100644
--- a/include/linux/list_lru.h
+++ b/include/linux/list_lru.h
@@ -8,6 +8,7 @@
 #define _LRU_LIST_H
 
 #include <linux/list.h>
+#include <linux/nodemask.h>
 
 /* list_lru_walk_cb has to always return one of those */
 enum lru_status {
@@ -18,11 +19,26 @@ enum lru_status {
 				   internally, but has to return locked. */
 };
 
-struct list_lru {
+struct list_lru_node {
 	spinlock_t		lock;
 	struct list_head	list;
 	/* kept as signed so we can catch imbalance bugs */
 	long			nr_items;
+} ____cacheline_aligned_in_smp;
+
+struct list_lru {
+	/*
+	 * Because we use a fixed-size array, this struct can be very big if
+	 * MAX_NUMNODES is big. If this becomes a problem this is fixable by
+	 * turning this into a pointer and dynamically allocating this to
+	 * nr_node_ids. This quantity is firwmare-provided, and still would
+	 * provide room for all nodes at the cost of a pointer lookup and an
+	 * extra allocation. Because that allocation will most likely come from
+	 * a different slab cache than the main structure holding this
+	 * structure, we may very well fail.
+	 */
+	struct list_lru_node	node[MAX_NUMNODES];
+	nodemask_t		active_nodes;
 };
 
 int list_lru_init(struct list_lru *lru);
@@ -66,10 +82,7 @@ bool list_lru_del(struct list_lru *lru, struct list_head *item);
  * guarantee that the list is not updated while the count is being computed.
  * Callers that want such a guarantee need to provide an outer lock.
  */
-static inline unsigned long list_lru_count(struct list_lru *lru)
-{
-	return lru->nr_items;
-}
+unsigned long list_lru_count(struct list_lru *lru);
 
 typedef enum lru_status
 (*list_lru_walk_cb)(struct list_head *item, spinlock_t *lock, void *cb_arg);
diff --git a/mm/list_lru.c b/mm/list_lru.c
index dd74c54..f2d1d6e 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -6,41 +6,73 @@
  */
 #include <linux/kernel.h>
 #include <linux/module.h>
+#include <linux/mm.h>
 #include <linux/list_lru.h>
 
 bool list_lru_add(struct list_lru *lru, struct list_head *item)
 {
-	spin_lock(&lru->lock);
+	int nid = page_to_nid(virt_to_page(item));
+	struct list_lru_node *nlru = &lru->node[nid];
+
+	spin_lock(&nlru->lock);
+	BUG_ON(nlru->nr_items < 0);
 	if (list_empty(item)) {
-		list_add_tail(item, &lru->list);
-		lru->nr_items++;
-		spin_unlock(&lru->lock);
+		list_add_tail(item, &nlru->list);
+		if (nlru->nr_items++ == 0)
+			node_set(nid, lru->active_nodes);
+		spin_unlock(&nlru->lock);
 		return true;
 	}
-	spin_unlock(&lru->lock);
+	spin_unlock(&nlru->lock);
 	return false;
 }
 EXPORT_SYMBOL_GPL(list_lru_add);
 
 bool list_lru_del(struct list_lru *lru, struct list_head *item)
 {
-	spin_lock(&lru->lock);
+	int nid = page_to_nid(virt_to_page(item));
+	struct list_lru_node *nlru = &lru->node[nid];
+
+	spin_lock(&nlru->lock);
 	if (!list_empty(item)) {
 		list_del_init(item);
-		lru->nr_items--;
-		spin_unlock(&lru->lock);
+		if (--nlru->nr_items == 0)
+			node_clear(nid, lru->active_nodes);
+		BUG_ON(nlru->nr_items < 0);
+		spin_unlock(&nlru->lock);
 		return true;
 	}
-	spin_unlock(&lru->lock);
+	spin_unlock(&nlru->lock);
 	return false;
 }
 EXPORT_SYMBOL_GPL(list_lru_del);
 
-unsigned long list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
-			    void *cb_arg, unsigned long nr_to_walk)
+unsigned long list_lru_count(struct list_lru *lru)
 {
+	unsigned long count = 0;
+	int nid;
+
+	for_each_node_mask(nid, lru->active_nodes) {
+		struct list_lru_node *nlru = &lru->node[nid];
+
+		spin_lock(&nlru->lock);
+		BUG_ON(nlru->nr_items < 0);
+		count += nlru->nr_items;
+		spin_unlock(&nlru->lock);
+	}
+
+	return count;
+}
+EXPORT_SYMBOL_GPL(list_lru_count);
+
+static unsigned long
+list_lru_walk_node(struct list_lru *lru, int nid, list_lru_walk_cb isolate,
+		   void *cb_arg, unsigned long *nr_to_walk)
+{
+
+	struct list_lru_node	*nlru = &lru->node[nid];
 	struct list_head *item, *n;
-	unsigned long removed = 0;
+	unsigned long isolated = 0;
 	/*
 	 * If we don't keep state of at which pass we are, we can loop at
 	 * LRU_RETRY, since we have no guarantees that the caller will be able
@@ -50,18 +82,20 @@ unsigned long list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
 	 */
 	bool first_pass = true;
 
-	spin_lock(&lru->lock);
+	spin_lock(&nlru->lock);
 restart:
-	list_for_each_safe(item, n, &lru->list) {
+	list_for_each_safe(item, n, &nlru->list) {
 		enum lru_status ret;
-		ret = isolate(item, &lru->lock, cb_arg);
+		ret = isolate(item, &nlru->lock, cb_arg);
 		switch (ret) {
 		case LRU_REMOVED:
-			lru->nr_items--;
-			removed++;
+			if (--nlru->nr_items == 0)
+				node_clear(nid, lru->active_nodes);
+			BUG_ON(nlru->nr_items < 0);
+			isolated++;
 			break;
 		case LRU_ROTATE:
-			list_move_tail(item, &lru->list);
+			list_move_tail(item, &nlru->list);
 			break;
 		case LRU_SKIP:
 			break;
@@ -76,42 +110,84 @@ restart:
 			BUG();
 		}
 
-		if (nr_to_walk-- == 0)
+		if ((*nr_to_walk)-- == 0)
 			break;
 
 	}
-	spin_unlock(&lru->lock);
-	return removed;
+
+	spin_unlock(&nlru->lock);
+	return isolated;
+}
+EXPORT_SYMBOL_GPL(list_lru_walk_node);
+
+unsigned long list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
+			    void *cb_arg, unsigned long nr_to_walk)
+{
+	unsigned long isolated = 0;
+	int nid;
+
+	for_each_node_mask(nid, lru->active_nodes) {
+		isolated += list_lru_walk_node(lru, nid, isolate,
+					       cb_arg, &nr_to_walk);
+		if (nr_to_walk <= 0)
+			break;
+	}
+	return isolated;
 }
 EXPORT_SYMBOL_GPL(list_lru_walk);
 
-unsigned long list_lru_dispose_all(struct list_lru *lru,
-				   list_lru_dispose_cb dispose)
+static unsigned long list_lru_dispose_all_node(struct list_lru *lru, int nid,
+					       list_lru_dispose_cb dispose)
 {
-	unsigned long disposed = 0;
+	struct list_lru_node	*nlru = &lru->node[nid];
 	LIST_HEAD(dispose_list);
+	unsigned long disposed = 0;
 
-	spin_lock(&lru->lock);
-	while (!list_empty(&lru->list)) {
-		list_splice_init(&lru->list, &dispose_list);
-		disposed += lru->nr_items;
-		lru->nr_items = 0;
-		spin_unlock(&lru->lock);
+	spin_lock(&nlru->lock);
+	while (!list_empty(&nlru->list)) {
+		list_splice_init(&nlru->list, &dispose_list);
+		disposed += nlru->nr_items;
+		nlru->nr_items = 0;
+		node_clear(nid, lru->active_nodes);
+		spin_unlock(&nlru->lock);
 
 		dispose(&dispose_list);
 
-		spin_lock(&lru->lock);
+		spin_lock(&nlru->lock);
 	}
-	spin_unlock(&lru->lock);
+	spin_unlock(&nlru->lock);
 	return disposed;
 }
 
+unsigned long list_lru_dispose_all(struct list_lru *lru,
+				   list_lru_dispose_cb dispose)
+{
+	unsigned long disposed;
+	unsigned long total = 0;
+	int nid;
+
+	do {
+		disposed = 0;
+		for_each_node_mask(nid, lru->active_nodes) {
+			disposed += list_lru_dispose_all_node(lru, nid,
+							      dispose);
+		}
+		total += disposed;
+	} while (disposed != 0);
+
+	return total;
+}
+
 int list_lru_init(struct list_lru *lru)
 {
-	spin_lock_init(&lru->lock);
-	INIT_LIST_HEAD(&lru->list);
-	lru->nr_items = 0;
+	int i;
 
+	nodes_clear(lru->active_nodes);
+	for (i = 0; i < MAX_NUMNODES; i++) {
+		spin_lock_init(&lru->node[i].lock);
+		INIT_LIST_HEAD(&lru->node[i].list);
+		lru->node[i].nr_items = 0;
+	}
 	return 0;
 }
 EXPORT_SYMBOL_GPL(list_lru_init);
-- 
1.8.1.4