[PATCH v10 28/35] list_lru: per-memcg walks

Glauber Costa
2013-06-03T19:29:57Z

This patch extend the list_lru interfaces to allow for a memcg
parameter. Because most of its users won't need it, instead of
modifying the function signatures we create a new set of _memcg()
functions and write the old API ontop of that.

Signed-off-by: Glauber Costa <glommer-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>
Cc: Dave Chinner <dchinner-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Mel Gorman <mgorman-l3A5Bk7waGM@public.gmane.org>
Cc: Rik van Riel <riel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
Cc: Michal Hocko <mhocko-AlSwsSmVLrQ@public.gmane.org>
c: Hugh Dickins <hughd-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org>
Cc: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
---
include/linux/list_lru.h | 26 +++++++++++--
include/linux/memcontrol.h | 2 +
lib/list_lru.c | 97 ++++++++++++++++++++++++++++++++++------------
3 files changed, 97 insertions(+), 28 deletions(-)

diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
index 3b8c301..dcb67dc 100644
--- a/include/linux/list_lru.h
+++ b/include/linux/list_lru.h
@@ -100,7 +100,15 @@ static inline int list_lru_init_memcg(struct list_lru *lru)
int list_lru_add(struct list_lru *lru, struct list_head *item);
int list_lru_del(struct list_lru *lru, struct list_head *item);

-unsigned long list_lru_count_node(struct list_lru *lru, int nid);
+unsigned long list_lru_count_node_memcg(struct list_lru *lru, int nid,
+ struct mem_cgroup *memcg);
+
+static inline unsigned long
+list_lru_count_node(struct list_lru *lru, int nid)
+{
+ return list_lru_count_node_memcg(lru, nid, NULL);
+}
+
static inline unsigned long list_lru_count(struct list_lru *lru)
{
long count = 0;
@@ -118,9 +126,19 @@ typedef enum lru_status
typedef void (*list_lru_dispose_cb)(struct list_head *dispose_list);

-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);
+unsigned long
+list_lru_walk_node_memcg(struct list_lru *lru, int nid,
+ list_lru_walk_cb isolate, void *cb_arg,
+ unsigned long *nr_to_walk, struct mem_cgroup *memcg);
+
+static inline 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)
+{
+ return list_lru_walk_node_memcg(lru, nid, isolate, cb_arg,
+ nr_to_walk, NULL);
+}

static inline unsigned long
list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 50f199f..3eeece8 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -593,6 +593,8 @@ static inline bool memcg_kmem_is_active(struct mem_cgroup *memcg)
#define for_each_memcg_cache_index(_idx) \
for (; NULL; )

+#define memcg_limited_groups_array_size 0
+
static inline bool memcg_kmem_enabled(void)
{
return false;
diff --git a/lib/list_lru.c b/lib/list_lru.c
index 128af5e..f919f99 100644
--- a/lib/list_lru.c
+++ b/lib/list_lru.c
@@ -50,13 +50,16 @@ lru_node_of_index(struct list_lru *lru, int index, int nid)
rcu_read_lock();
rmb();
/*
- * The array exist, but the particular memcg does not. That is an
- * impossible situation: it would mean we are trying to add to a list
- * belonging to a memcg that does not exist. Either wasn't created or
- * has been already freed. In both cases it should no longer have
- * objects. BUG_ON to avoid a NULL dereference.
+ * The array exist, but the particular memcg does not. This cannot
+ * happen when we are called from memcg_kmem_lru_of_page with a
+ * definite memcg, but it can happen when we are iterating over all
+ * memcgs (for instance, when disposing all lists.
*/
- BUG_ON(!lru->memcg_lrus[index]);
+ if (!lru->memcg_lrus[index]) {
+ rcu_read_unlock();
+ return NULL;
+ }
+
nlru = &lru->memcg_lrus[index]->node[nid];
rcu_read_unlock();
return nlru;
@@ -80,6 +83,23 @@ memcg_kmem_lru_of_page(struct list_lru *lru, struct page *page)
return lru_node_of_index(lru, memcg_id, nid);
}

+/*
+ * This helper will loop through all node-data in the LRU, either global or
+ * per-memcg. If memcg is either not present or not used,
+ * memcg_limited_groups_array_size will be 0. _idx starts at -1, and it will
+ * still be allowed to execute once.
+ *
+ * We convention that for _idx = -1, the global node info should be used.
+ * After that, we will go through each of the memcgs, starting at 0.
+ *
+ * We don't need any kind of locking for the loop because
+ * memcg_limited_groups_array_size can only grow, gaining new fields at the
+ * end. The old ones are just copied, and any interesting manipulation happen
+ * in the node list itself, and we already lock the list.
+ */
+#define for_each_memcg_lru_index(_idx) \
+ for ((_idx) = -1; ((_idx) < memcg_limited_groups_array_size); (_idx)++)
+
int
list_lru_add(
struct list_lru *lru,
@@ -139,10 +159,19 @@ list_lru_del(
EXPORT_SYMBOL_GPL(list_lru_del);

unsigned long
-list_lru_count_node(struct list_lru *lru, int nid)
+list_lru_count_node_memcg(struct list_lru *lru, int nid,
+ struct mem_cgroup *memcg)
{
long count = 0;
- struct list_lru_node *nlru = &lru->node[nid];
+ int memcg_id = -1;
+ struct list_lru_node *nlru;
+
+ if (memcg && memcg_kmem_is_active(memcg))
+ memcg_id = memcg_cache_id(memcg);
+
+ nlru = lru_node_of_index(lru, memcg_id, nid);
+ if (!nlru)
+ return 0;

spin_lock(&nlru->lock);
BUG_ON(nlru->nr_items < 0);
@@ -151,19 +180,28 @@ list_lru_count_node(struct list_lru *lru, int nid)

return count;
}
-EXPORT_SYMBOL_GPL(list_lru_count_node);
+EXPORT_SYMBOL_GPL(list_lru_count_node_memcg);

unsigned long
-list_lru_walk_node(
+list_lru_walk_node_memcg(
struct list_lru *lru,
int nid,
list_lru_walk_cb isolate,
void *cb_arg,
- unsigned long *nr_to_walk)
+ unsigned long *nr_to_walk,
+ struct mem_cgroup *memcg)
{
- struct list_lru_node *nlru = &lru->node[nid];
struct list_head *item, *n;
unsigned long isolated = 0;
+ struct list_lru_node *nlru;
+ int memcg_id = -1;
+
+ if (memcg && memcg_kmem_is_active(memcg))
+ memcg_id = memcg_cache_id(memcg);
+
+ nlru = lru_node_of_index(lru, memcg_id, nid);
+ if (!nlru)
+ return 0;

spin_lock(&nlru->lock);
list_for_each_safe(item, n, &nlru->list) {
@@ -200,7 +238,7 @@ restart:
spin_unlock(&nlru->lock);
return isolated;
}
-EXPORT_SYMBOL_GPL(list_lru_walk_node);
+EXPORT_SYMBOL_GPL(list_lru_walk_node_memcg);

static unsigned long
list_lru_dispose_all_node(
@@ -208,23 +246,34 @@ list_lru_dispose_all_node(
int nid,
list_lru_dispose_cb dispose)
{
- struct list_lru_node *nlru = &lru->node[nid];
+ struct list_lru_node *nlru;
LIST_HEAD(dispose_list);
unsigned long disposed = 0;
+ int idx;

- 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);
+ for_each_memcg_lru_index(idx) {
+ nlru = lru_node_of_index(lru, idx, nid);
+ if (!nlru)
+ continue;

spin_lock(&nlru->lock);
+ while (!list_empty(&nlru->list)) {
+ list_splice_init(&nlru->list, &dispose_list);
+
+ if (atomic_long_sub_and_test(nlru->nr_items,
+ &lru->node_totals[nid]))
+ node_clear(nid, lru->active_nodes);
+ disposed += nlru->nr_items;
+ nlru->nr_items = 0;
+ spin_unlock(&nlru->lock);
+
+ dispose(&dispose_list);
+
+ spin_lock(&nlru->lock);
+ }
+ spin_unlock(&nlru->lock);
}
- spin_unlock(&nlru->lock);
+
return disposed;
}

--
1.8.1.4