blk-cgroup: Add unaccounted time to timeslice_used.

There are two kind of times that tasks are not charged for: the first
seek and the extra time slice used over the allocated timeslice. Both
of these exported as a new unaccounted_time stat.

I think it would be good to have this reported in 'time' as well, but
that is probably a separate discussion.

Signed-off-by: Justin TerAvest <teravest@google.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

4 files changed, 41 insertions, 14 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 455768a3eb9..77ee3c1ec1a 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -371,12 +371,14 @@ void blkiocg_update_io_remove_stats(struct blkio_group *blkg,
 }
 EXPORT_SYMBOL_GPL(blkiocg_update_io_remove_stats);
 
-void blkiocg_update_timeslice_used(struct blkio_group *blkg, unsigned long time)
+void blkiocg_update_timeslice_used(struct blkio_group *blkg, unsigned long time,
+                                unsigned long unaccounted_time)
 {
         unsigned long flags;
 
         spin_lock_irqsave(&blkg->stats_lock, flags);
         blkg->stats.time += time;
+        blkg->stats.unaccounted_time += unaccounted_time;
         spin_unlock_irqrestore(&blkg->stats_lock, flags);
 }
 EXPORT_SYMBOL_GPL(blkiocg_update_timeslice_used);
@@ -603,6 +605,9 @@ static uint64_t blkio_get_stat(struct blkio_group *blkg,
         if (type == BLKIO_STAT_SECTORS)
                 return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
                                         blkg->stats.sectors, cb, dev);
+        if (type == BLKIO_STAT_UNACCOUNTED_TIME)
+                return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
+                                        blkg->stats.unaccounted_time, cb, dev);
 #ifdef CONFIG_DEBUG_BLK_CGROUP
         if (type == BLKIO_STAT_AVG_QUEUE_SIZE) {
                 uint64_t sum = blkg->stats.avg_queue_size_sum;
@@ -1106,6 +1111,9 @@ static int blkiocg_file_read_map(struct cgroup *cgrp, struct cftype *cft,
                 case BLKIO_PROP_sectors:
                         return blkio_read_blkg_stats(blkcg, cft, cb,
                                                 BLKIO_STAT_SECTORS, 0);
+                case BLKIO_PROP_unaccounted_time:
+                        return blkio_read_blkg_stats(blkcg, cft, cb,
+                                                BLKIO_STAT_UNACCOUNTED_TIME, 0);
                 case BLKIO_PROP_io_service_bytes:
                         return blkio_read_blkg_stats(blkcg, cft, cb,
                                                 BLKIO_STAT_SERVICE_BYTES, 1);
@@ -1262,6 +1270,12 @@ struct cftype blkio_files[] = {
                 .read_map = blkiocg_file_read_map,
         },
         {
+                .name = "unaccounted_time",
+                .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
+                                BLKIO_PROP_unaccounted_time),
+                .read_map = blkiocg_file_read_map,
+        },
+        {
                 .name = "io_service_bytes",
                 .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
                                 BLKIO_PROP_io_service_bytes),
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 57e7234c5ae..10919fae2d3 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -49,6 +49,8 @@ enum stat_type {
         /* All the single valued stats go below this */
         BLKIO_STAT_TIME,
         BLKIO_STAT_SECTORS,
+        /* Time not charged to this cgroup */
+        BLKIO_STAT_UNACCOUNTED_TIME,
 #ifdef CONFIG_DEBUG_BLK_CGROUP
         BLKIO_STAT_AVG_QUEUE_SIZE,
         BLKIO_STAT_IDLE_TIME,
@@ -81,6 +83,7 @@ enum blkcg_file_name_prop {
         BLKIO_PROP_io_serviced,
         BLKIO_PROP_time,
         BLKIO_PROP_sectors,
+        BLKIO_PROP_unaccounted_time,
         BLKIO_PROP_io_service_time,
         BLKIO_PROP_io_wait_time,
         BLKIO_PROP_io_merged,
@@ -114,6 +117,8 @@ struct blkio_group_stats {
         /* total disk time and nr sectors dispatched by this group */
         uint64_t time;
         uint64_t sectors;
+        /* Time not charged to this cgroup */
+        uint64_t unaccounted_time;
         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 */
@@ -293,7 +298,8 @@ extern int blkiocg_del_blkio_group(struct blkio_group *blkg);
 extern struct blkio_group *blkiocg_lookup_group(struct blkio_cgroup *blkcg,
                                                 void *key);
 void blkiocg_update_timeslice_used(struct blkio_group *blkg,
-                                        unsigned long time);
+                                        unsigned long time,
+                                        unsigned long unaccounted_time);
 void blkiocg_update_dispatch_stats(struct blkio_group *blkg, uint64_t bytes,
                                                 bool direction, bool sync);
 void blkiocg_update_completion_stats(struct blkio_group *blkg,
@@ -319,7 +325,9 @@ blkiocg_del_blkio_group(struct blkio_group *blkg) { return 0; }
 static inline struct blkio_group *
 blkiocg_lookup_group(struct blkio_cgroup *blkcg, void *key) { return NULL; }
 static inline void blkiocg_update_timeslice_used(struct blkio_group *blkg,
-                                                unsigned long time) {}
+                                                unsigned long time,
+                                                unsigned long unaccounted_time)
+{}
 static inline void blkiocg_update_dispatch_stats(struct blkio_group *blkg,
                                 uint64_t bytes, bool direction, bool sync) {}
 static inline void blkiocg_update_completion_stats(struct blkio_group *blkg,
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index c826ef81c67..89e0d1cc14b 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -899,7 +899,8 @@ cfq_group_service_tree_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
         cfq_blkiocg_update_dequeue_stats(&cfqg->blkg, 1);
 }
 
-static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq)
+static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq,
+                                                unsigned int *unaccounted_time)
 {
         unsigned int slice_used;
 
@@ -918,8 +919,13 @@ static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq)
                                         1);
         } else {
                 slice_used = jiffies - cfqq->slice_start;
-                if (slice_used > cfqq->allocated_slice)
+                if (slice_used > cfqq->allocated_slice) {
+                        *unaccounted_time = slice_used - cfqq->allocated_slice;
                         slice_used = cfqq->allocated_slice;
+                }
+                if (time_after(cfqq->slice_start, cfqq->dispatch_start))
+                        *unaccounted_time += cfqq->slice_start -
+                                        cfqq->dispatch_start;
         }
 
         return slice_used;
@@ -929,12 +935,12 @@ static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
                                 struct cfq_queue *cfqq)
 {
         struct cfq_rb_root *st = &cfqd->grp_service_tree;
-        unsigned int used_sl, charge;
+        unsigned int used_sl, charge, unaccounted_sl = 0;
         int nr_sync = cfqg->nr_cfqq - cfqg_busy_async_queues(cfqd, cfqg)
                         - cfqg->service_tree_idle.count;
 
         BUG_ON(nr_sync < 0);
-        used_sl = charge = cfq_cfqq_slice_usage(cfqq);
+        used_sl = charge = cfq_cfqq_slice_usage(cfqq, &unaccounted_sl);
 
         if (iops_mode(cfqd))
                 charge = cfqq->slice_dispatch;
@@ -960,7 +966,8 @@ static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
         cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u disp=%u charge=%u iops=%u"
                         " sect=%u", used_sl, cfqq->slice_dispatch, charge,
                         iops_mode(cfqd), cfqq->nr_sectors);
-        cfq_blkiocg_update_timeslice_used(&cfqg->blkg, used_sl);
+        cfq_blkiocg_update_timeslice_used(&cfqg->blkg, used_sl,
+                                          unaccounted_sl);
         cfq_blkiocg_set_start_empty_time(&cfqg->blkg);
 }
 
@@ -3296,9 +3303,7 @@ static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
         BUG_ON(!cfq_cfqq_on_rr(cfqq));
 
         cfq_service_tree_add(cfqd, cfqq, 1);
-
-        cfqq->slice_end = 0;
-        cfq_mark_cfqq_slice_new(cfqq);
+        __cfq_set_active_queue(cfqd, cfqq);
 }
 
 /*
diff --git a/block/cfq.h b/block/cfq.h
index 54a6d90f8e8..2a155927e37 100644
--- a/block/cfq.h
+++ b/block/cfq.h
@@ -16,9 +16,9 @@ static inline void cfq_blkiocg_update_dequeue_stats(struct blkio_group *blkg,
 }
 
 static inline void cfq_blkiocg_update_timeslice_used(struct blkio_group *blkg,
-                        unsigned long time)
+                        unsigned long time, unsigned long unaccounted_time)
 {
-        blkiocg_update_timeslice_used(blkg, time);
+        blkiocg_update_timeslice_used(blkg, time, unaccounted_time);
 }
 
 static inline void cfq_blkiocg_set_start_empty_time(struct blkio_group *blkg)
@@ -85,7 +85,7 @@ static inline void cfq_blkiocg_update_dequeue_stats(struct blkio_group *blkg,
                         unsigned long dequeue) {}
 
 static inline void cfq_blkiocg_update_timeslice_used(struct blkio_group *blkg,
-                        unsigned long time) {}
+                        unsigned long time, unsigned long unaccounted_time) {}
 static inline void cfq_blkiocg_set_start_empty_time(struct blkio_group *blkg) {}
 static inline void cfq_blkiocg_update_io_remove_stats(struct blkio_group *blkg,
                                 bool direction, bool sync) {}