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blkio: Add io_merged stat

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This includes both the number of bios merged into requests belonging to this
cgroup as well as the number of requests merged together.
In the past, we've observed different merging behavior across upstream kernels,
some by design some actual bugs. This stat helps a lot in debugging such
problems when applications report decreased throughput with a new kernel
version.

This needed adding an extra elevator function to capture bios being merged as I
did not want to pollute elevator code with blkiocg knowledge and hence needed
the accounting invocation to come from CFQ.

Signed-off-by: Divyesh Shah<[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
This commit is contained in:
Divyesh Shah 2010-04-08 21:14:23 -07:00 • committed by Jens Axboe
commit 812d402648
7 changed files with 57 additions and 1 deletions
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17
block/blk-cgroup.c
View file

@ -127,6 +127,18 @@ void blkiocg_update_completion_stats(struct blkio_group *blkg,
}
EXPORT_SYMBOL_GPL(blkiocg_update_completion_stats);
void blkiocg_update_io_merged_stats(struct blkio_group *blkg, bool direction,
bool sync)
{
unsigned long flags;
spin_lock_irqsave(&blkg->stats_lock, flags);
blkio_add_stat(blkg->stats.stat_arr[BLKIO_STAT_MERGED], 1, direction,
sync);
spin_unlock_irqrestore(&blkg->stats_lock, flags);
}
EXPORT_SYMBOL_GPL(blkiocg_update_io_merged_stats);
void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
struct blkio_group *blkg, void *key, dev_t dev)
{
@ -363,6 +375,7 @@ SHOW_FUNCTION_PER_GROUP(io_service_bytes, BLKIO_STAT_SERVICE_BYTES, 1);
SHOW_FUNCTION_PER_GROUP(io_serviced, BLKIO_STAT_SERVICED, 1);
SHOW_FUNCTION_PER_GROUP(io_service_time, BLKIO_STAT_SERVICE_TIME, 1);
SHOW_FUNCTION_PER_GROUP(io_wait_time, BLKIO_STAT_WAIT_TIME, 1);
SHOW_FUNCTION_PER_GROUP(io_merged, BLKIO_STAT_MERGED, 1);
#ifdef CONFIG_DEBUG_BLK_CGROUP
SHOW_FUNCTION_PER_GROUP(dequeue, BLKIO_STAT_DEQUEUE, 0);
#endif
@ -407,6 +420,10 @@ struct cftype blkio_files[] = {
.name = "io_wait_time",
.read_map = blkiocg_io_wait_time_read,
},
{
.name = "io_merged",
.read_map = blkiocg_io_merged_read,
},
{
.name = "reset_stats",
.write_u64 = blkiocg_reset_stats,

8
block/blk-cgroup.h
View file

@ -34,6 +34,8 @@ enum stat_type {
BLKIO_STAT_SERVICED,
/* Total time spent waiting in scheduler queue in ns */
BLKIO_STAT_WAIT_TIME,
/* Number of IOs merged */
BLKIO_STAT_MERGED,
/* All the single valued stats go below this */
BLKIO_STAT_TIME,
BLKIO_STAT_SECTORS,
@ -61,7 +63,7 @@ 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_WAIT_TIME + 1][BLKIO_STAT_TOTAL];
uint64_t stat_arr[BLKIO_STAT_MERGED + 1][BLKIO_STAT_TOTAL];
#ifdef CONFIG_DEBUG_BLK_CGROUP
/* How many times this group has been removed from service tree */
unsigned long dequeue;
@ -148,6 +150,8 @@ 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,
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);
#else
struct cgroup;
static inline struct blkio_cgroup *
@ -169,5 +173,7 @@ static inline void blkiocg_update_dispatch_stats(struct blkio_group *blkg,
static inline void blkiocg_update_completion_stats(struct blkio_group *blkg,
uint64_t start_time, uint64_t io_start_time, bool direction,
bool sync) {}
static inline void blkiocg_update_io_merged_stats(struct blkio_group *blkg,
bool direction, bool sync) {}
#endif
#endif /* _BLK_CGROUP_H */

2
block/blk-core.c
View file

@ -1202,6 +1202,7 @@ static int __make_request(struct request_queue *q, struct bio *bio)
if (!blk_rq_cpu_valid(req))
req->cpu = bio->bi_comp_cpu;
drive_stat_acct(req, 0);
elv_bio_merged(q, req, bio);
if (!attempt_back_merge(q, req))
elv_merged_request(q, req, el_ret);
goto out;
@ -1235,6 +1236,7 @@ static int __make_request(struct request_queue *q, struct bio *bio)
if (!blk_rq_cpu_valid(req))
req->cpu = bio->bi_comp_cpu;
drive_stat_acct(req, 0);
elv_bio_merged(q, req, bio);
if (!attempt_front_merge(q, req))
elv_merged_request(q, req, el_ret);
goto out;

11
block/cfq-iosched.c
View file

@ -1467,6 +1467,14 @@ static void cfq_merged_request(struct request_queue *q, struct request *req,
}
}
static void cfq_bio_merged(struct request_queue *q, struct request *req,
struct bio *bio)
{
struct cfq_queue *cfqq = RQ_CFQQ(req);
blkiocg_update_io_merged_stats(&cfqq->cfqg->blkg, bio_data_dir(bio),
cfq_bio_sync(bio));
}
static void
cfq_merged_requests(struct request_queue *q, struct request *rq,
struct request *next)
@ -1484,6 +1492,8 @@ cfq_merged_requests(struct request_queue *q, struct request *rq,
if (cfqq->next_rq == next)
cfqq->next_rq = rq;
cfq_remove_request(next);
blkiocg_update_io_merged_stats(&cfqq->cfqg->blkg, rq_data_dir(next),
rq_is_sync(next));
}
static int cfq_allow_merge(struct request_queue *q, struct request *rq,
@ -3861,6 +3871,7 @@ static struct elevator_type iosched_cfq = {
.elevator_merged_fn = cfq_merged_request,
.elevator_merge_req_fn = cfq_merged_requests,
.elevator_allow_merge_fn = cfq_allow_merge,
.elevator_bio_merged_fn = cfq_bio_merged,
.elevator_dispatch_fn = cfq_dispatch_requests,
.elevator_add_req_fn = cfq_insert_request,
.elevator_activate_req_fn = cfq_activate_request,

9
block/elevator.c
View file

@ -539,6 +539,15 @@ void elv_merge_requests(struct request_queue *q, struct request *rq,
q->last_merge = rq;
}
void elv_bio_merged(struct request_queue *q, struct request *rq,
struct bio *bio)
{
struct elevator_queue *e = q->elevator;
if (e->ops->elevator_bio_merged_fn)
e->ops->elevator_bio_merged_fn(q, rq, bio);
}
void elv_requeue_request(struct request_queue *q, struct request *rq)
{
/*