blk-throttle: Make dispatch stats per cpu

Currently we take blkg_stat lock for even updating the stats. So even if
a group has no throttling rules (common case for root group), we end
up taking blkg_lock, for updating the stats.

Make dispatch stats per cpu so that these can be updated without taking
blkg lock.

If cpu goes offline, these stats simply disappear. No protection has
been provided for that yet. Do we really need anything for that?

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

1 files changed, 21 insertions, 6 deletions

diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 63f1ef4450d7..fd730a24b491 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -36,10 +36,6 @@ enum stat_type {
          * request completion for IOs doen by this cgroup. This may not be
          * accurate when NCQ is turned on. */
         BLKIO_STAT_SERVICE_TIME = 0,
-        /* Total bytes transferred */
-        BLKIO_STAT_SERVICE_BYTES,
-        /* Total IOs serviced, post merge */
-        BLKIO_STAT_SERVICED,
         /* Total time spent waiting in scheduler queue in ns */
         BLKIO_STAT_WAIT_TIME,
         /* Number of IOs merged */
@@ -48,7 +44,6 @@ enum stat_type {
         BLKIO_STAT_QUEUED,
         /* All the single valued stats go below this */
         BLKIO_STAT_TIME,
-        BLKIO_STAT_SECTORS,
 #ifdef CONFIG_DEBUG_BLK_CGROUP
         /* Time not charged to this cgroup */
         BLKIO_STAT_UNACCOUNTED_TIME,
@@ -60,6 +55,16 @@ enum stat_type {
 #endif
 };
 
+/* Per cpu stats */
+enum stat_type_cpu {
+        BLKIO_STAT_CPU_SECTORS,
+        /* Total bytes transferred */
+        BLKIO_STAT_CPU_SERVICE_BYTES,
+        /* Total IOs serviced, post merge */
+        BLKIO_STAT_CPU_SERVICED,
+        BLKIO_STAT_CPU_NR
+};
+
 enum stat_sub_type {
         BLKIO_STAT_READ = 0,
         BLKIO_STAT_WRITE,
@@ -116,7 +121,6 @@ struct blkio_cgroup {
 struct blkio_group_stats {
         /* total disk time and nr sectors dispatched by this group */
         uint64_t time;
-        uint64_t sectors;
         uint64_t stat_arr[BLKIO_STAT_QUEUED + 1][BLKIO_STAT_TOTAL];
 #ifdef CONFIG_DEBUG_BLK_CGROUP
         /* Time not charged to this cgroup */
@@ -146,6 +150,12 @@ struct blkio_group_stats {
 #endif
 };
 
+/* Per cpu blkio group stats */
+struct blkio_group_stats_cpu {
+        uint64_t sectors;
+        uint64_t stat_arr_cpu[BLKIO_STAT_CPU_NR][BLKIO_STAT_TOTAL];
+};
+
 struct blkio_group {
         /* An rcu protected unique identifier for the group */
         void *key;
@@ -161,6 +171,8 @@ struct blkio_group {
         /* Need to serialize the stats in the case of reset/update */
         spinlock_t stats_lock;
         struct blkio_group_stats stats;
+        /* Per cpu stats pointer */
+        struct blkio_group_stats_cpu __percpu *stats_cpu;
 };
 
 struct blkio_policy_node {
@@ -296,6 +308,7 @@ extern struct blkio_cgroup *task_blkio_cgroup(struct task_struct *tsk);
 extern void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
         struct blkio_group *blkg, void *key, dev_t dev,
         enum blkio_policy_id plid);
+extern int blkio_alloc_blkg_stats(struct blkio_group *blkg);
 extern int blkiocg_del_blkio_group(struct blkio_group *blkg);
 extern struct blkio_group *blkiocg_lookup_group(struct blkio_cgroup *blkcg,
                                                 void *key);
@@ -323,6 +336,8 @@ static inline void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
                 struct blkio_group *blkg, void *key, dev_t dev,
                 enum blkio_policy_id plid) {}
 
+static inline int blkio_alloc_blkg_stats(struct blkio_group *blkg) { return 0; }
+
 static inline int
 blkiocg_del_blkio_group(struct blkio_group *blkg) { return 0; }