blkio: Add io_queued and avg_queue_size stats

These stats are useful for getting a feel for the queue depth of the cgroup,
i.e., how filled up its queues are at a given instant and over the existence of
the cgroup. This ability is useful when debugging problems in the wild as it
helps understand the application's IO pattern w/o having to read through the
userspace code (coz its tedious or just not available) or w/o the ability
to run blktrace (since you may not have root access and/or not want to disturb
performance).

Signed-off-by: Divyesh Shah<dpshah@google.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 19 insertions, 1 deletions

diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 470a29db6bec..bea7f3b9a88e 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -36,10 +36,13 @@ enum stat_type {
         BLKIO_STAT_WAIT_TIME,
         /* Number of IOs merged */
         BLKIO_STAT_MERGED,
+        /* Number of IOs queued up */
+        BLKIO_STAT_QUEUED,
         /* All the single valued stats go below this */
         BLKIO_STAT_TIME,
         BLKIO_STAT_SECTORS,
 #ifdef CONFIG_DEBUG_BLK_CGROUP
+        BLKIO_STAT_AVG_QUEUE_SIZE,
         BLKIO_STAT_DEQUEUE
 #endif
 };
@@ -63,8 +66,12 @@ 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_MERGED + 1][BLKIO_STAT_TOTAL];
+        uint64_t stat_arr[BLKIO_STAT_QUEUED + 1][BLKIO_STAT_TOTAL];
 #ifdef CONFIG_DEBUG_BLK_CGROUP
+        /* Sum of number of IOs queued across all samples */
+        uint64_t avg_queue_size_sum;
+        /* Count of samples taken for average */
+        uint64_t avg_queue_size_samples;
         /* How many times this group has been removed from service tree */
         unsigned long dequeue;
 #endif
@@ -127,10 +134,13 @@ static inline char *blkg_path(struct blkio_group *blkg)
 {
         return blkg->path;
 }
+void blkiocg_update_set_active_queue_stats(struct blkio_group *blkg);
 void blkiocg_update_dequeue_stats(struct blkio_group *blkg,
                                 unsigned long dequeue);
 #else
 static inline char *blkg_path(struct blkio_group *blkg) { return NULL; }
+static inline void blkiocg_update_set_active_queue_stats(
+                                                struct blkio_group *blkg) {}
 static inline void blkiocg_update_dequeue_stats(struct blkio_group *blkg,
                                                 unsigned long dequeue) {}
 #endif
@@ -152,6 +162,10 @@ void blkiocg_update_completion_stats(struct blkio_group *blkg,
         uint64_t start_time, uint64_t io_start_time, bool direction, bool sync);
 void blkiocg_update_io_merged_stats(struct blkio_group *blkg, bool direction,
                                         bool sync);
+void blkiocg_update_request_add_stats(struct blkio_group *blkg,
+                struct blkio_group *curr_blkg, bool direction, bool sync);
+void blkiocg_update_request_remove_stats(struct blkio_group *blkg,
+                                        bool direction, bool sync);
 #else
 struct cgroup;
 static inline struct blkio_cgroup *
@@ -175,5 +189,9 @@ static inline void blkiocg_update_completion_stats(struct blkio_group *blkg,
                 bool sync) {}
 static inline void blkiocg_update_io_merged_stats(struct blkio_group *blkg,
                                                 bool direction, bool sync) {}
+static inline void blkiocg_update_request_add_stats(struct blkio_group *blkg,
+                struct blkio_group *curr_blkg, bool direction, bool sync) {}
+static inline void blkiocg_update_request_remove_stats(struct blkio_group *blkg,
+                                                bool direction, bool sync) {}
 #endif
 #endif /* _BLK_CGROUP_H */