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block, bfq: move debug blkio stats behind CONFIG_DEBUG_BLK_CGROUP

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BFQ currently creates, and updates, its own instance of the whole
set of blkio statistics that cfq creates. Yet, from the comments
of Tejun Heo in [1], it turned out that most of these statistics
are meant/useful only for debugging. This commit makes BFQ create
the latter, debugging statistics only if the option
CONFIG_DEBUG_BLK_CGROUP is set.

By doing so, this commit also enables BFQ to enjoy a high perfomance
boost. The reason is that, if CONFIG_DEBUG_BLK_CGROUP is not set, then
BFQ has to update far fewer statistics, and, in particular, not the
heaviest to update.  To give an idea of the benefits, if
CONFIG_DEBUG_BLK_CGROUP is not set, then, on an Intel i7-4850HQ, and
with 8 threads doing random I/O in parallel on null_blk (configured
with 0 latency), the throughput of BFQ grows from 310 to 400 KIOPS
(+30%). We have measured similar or even much higher boosts with other
CPUs: e.g., +45% with an ARM CortexTM-A53 Octa-core. Our results have
been obtained and can be reproduced very easily with the script in [1].

[1] https://www.spinics.net/lists/linux-block/msg18943.html

Suggested-by: Tejun Heo <[email protected]>
Suggested-by: Ulf Hansson <[email protected]>
Tested-by: Lee Tibbert <[email protected]>
Tested-by: Oleksandr Natalenko <[email protected]>
Signed-off-by: Luca Miccio <[email protected]>
Signed-off-by: Paolo Valente <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
This commit is contained in:
Luca Miccio 2017-11-13 07:34:10 +01:00 • committed by Jens Axboe
commit a33801e8b4
4 changed files with 125 additions and 79 deletions
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148
block/bfq-cgroup.c
View file

@ -24,7 +24,7 @@
#include "bfq-iosched.h"
#ifdef CONFIG_BFQ_GROUP_IOSCHED
#if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP)
/* bfqg stats flags */
enum bfqg_stats_flags {
@ -152,6 +152,57 @@ void bfqg_stats_update_avg_queue_size(struct bfq_group *bfqg)
bfqg_stats_update_group_wait_time(stats);
}
void bfqg_stats_update_io_add(struct bfq_group *bfqg, struct bfq_queue *bfqq,
unsigned int op)
{
blkg_rwstat_add(&bfqg->stats.queued, op, 1);
bfqg_stats_end_empty_time(&bfqg->stats);
if (!(bfqq == ((struct bfq_data *)bfqg->bfqd)->in_service_queue))
bfqg_stats_set_start_group_wait_time(bfqg, bfqq_group(bfqq));
}
void bfqg_stats_update_io_remove(struct bfq_group *bfqg, unsigned int op)
{
blkg_rwstat_add(&bfqg->stats.queued, op, -1);
}
void bfqg_stats_update_io_merged(struct bfq_group *bfqg, unsigned int op)
{
blkg_rwstat_add(&bfqg->stats.merged, op, 1);
}
void bfqg_stats_update_completion(struct bfq_group *bfqg, uint64_t start_time,
uint64_t io_start_time, unsigned int op)
{
struct bfqg_stats *stats = &bfqg->stats;
unsigned long long now = sched_clock();
if (time_after64(now, io_start_time))
blkg_rwstat_add(&stats->service_time, op,
now - io_start_time);
if (time_after64(io_start_time, start_time))
blkg_rwstat_add(&stats->wait_time, op,
io_start_time - start_time);
}
#else /* CONFIG_BFQ_GROUP_IOSCHED && CONFIG_DEBUG_BLK_CGROUP */
void bfqg_stats_update_io_add(struct bfq_group *bfqg, struct bfq_queue *bfqq,
unsigned int op) { }
void bfqg_stats_update_io_remove(struct bfq_group *bfqg, unsigned int op) { }
void bfqg_stats_update_io_merged(struct bfq_group *bfqg, unsigned int op) { }
void bfqg_stats_update_completion(struct bfq_group *bfqg, uint64_t start_time,
uint64_t io_start_time, unsigned int op) { }
void bfqg_stats_update_dequeue(struct bfq_group *bfqg) { }
void bfqg_stats_set_start_empty_time(struct bfq_group *bfqg) { }
void bfqg_stats_update_idle_time(struct bfq_group *bfqg) { }
void bfqg_stats_set_start_idle_time(struct bfq_group *bfqg) { }
void bfqg_stats_update_avg_queue_size(struct bfq_group *bfqg) { }
#endif /* CONFIG_BFQ_GROUP_IOSCHED && CONFIG_DEBUG_BLK_CGROUP */
#ifdef CONFIG_BFQ_GROUP_IOSCHED
/*
* blk-cgroup policy-related handlers
* The following functions help in converting between blk-cgroup
@ -229,42 +280,10 @@ void bfqg_and_blkg_put(struct bfq_group *bfqg)
blkg_put(bfqg_to_blkg(bfqg));
}
void bfqg_stats_update_io_add(struct bfq_group *bfqg, struct bfq_queue *bfqq,
unsigned int op)
{
blkg_rwstat_add(&bfqg->stats.queued, op, 1);
bfqg_stats_end_empty_time(&bfqg->stats);
if (!(bfqq == ((struct bfq_data *)bfqg->bfqd)->in_service_queue))
bfqg_stats_set_start_group_wait_time(bfqg, bfqq_group(bfqq));
}
void bfqg_stats_update_io_remove(struct bfq_group *bfqg, unsigned int op)
{
blkg_rwstat_add(&bfqg->stats.queued, op, -1);
}
void bfqg_stats_update_io_merged(struct bfq_group *bfqg, unsigned int op)
{
blkg_rwstat_add(&bfqg->stats.merged, op, 1);
}
void bfqg_stats_update_completion(struct bfq_group *bfqg, uint64_t start_time,
uint64_t io_start_time, unsigned int op)
{
struct bfqg_stats *stats = &bfqg->stats;
unsigned long long now = sched_clock();
if (time_after64(now, io_start_time))
blkg_rwstat_add(&stats->service_time, op,
now - io_start_time);
if (time_after64(io_start_time, start_time))
blkg_rwstat_add(&stats->wait_time, op,
io_start_time - start_time);
}
/* @stats = 0 */
static void bfqg_stats_reset(struct bfqg_stats *stats)
{
#ifdef CONFIG_DEBUG_BLK_CGROUP
/* queued stats shouldn't be cleared */
blkg_rwstat_reset(&stats->merged);
blkg_rwstat_reset(&stats->service_time);
@ -276,6 +295,7 @@ static void bfqg_stats_reset(struct bfqg_stats *stats)
blkg_stat_reset(&stats->group_wait_time);
blkg_stat_reset(&stats->idle_time);
blkg_stat_reset(&stats->empty_time);
#endif
}
/* @to += @from */
@ -284,6 +304,7 @@ static void bfqg_stats_add_aux(struct bfqg_stats *to, struct bfqg_stats *from)
if (!to || !from)
return;
#ifdef CONFIG_DEBUG_BLK_CGROUP
/* queued stats shouldn't be cleared */
blkg_rwstat_add_aux(&to->merged, &from->merged);
blkg_rwstat_add_aux(&to->service_time, &from->service_time);
@ -296,6 +317,7 @@ static void bfqg_stats_add_aux(struct bfqg_stats *to, struct bfqg_stats *from)
blkg_stat_add_aux(&to->group_wait_time, &from->group_wait_time);
blkg_stat_add_aux(&to->idle_time, &from->idle_time);
blkg_stat_add_aux(&to->empty_time, &from->empty_time);
#endif
}
/*
@ -342,6 +364,7 @@ void bfq_init_entity(struct bfq_entity *entity, struct bfq_group *bfqg)
static void bfqg_stats_exit(struct bfqg_stats *stats)
{
#ifdef CONFIG_DEBUG_BLK_CGROUP
blkg_rwstat_exit(&stats->merged);
blkg_rwstat_exit(&stats->service_time);
blkg_rwstat_exit(&stats->wait_time);
@ -353,10 +376,12 @@ static void bfqg_stats_exit(struct bfqg_stats *stats)
blkg_stat_exit(&stats->group_wait_time);
blkg_stat_exit(&stats->idle_time);
blkg_stat_exit(&stats->empty_time);
#endif
}
static int bfqg_stats_init(struct bfqg_stats *stats, gfp_t gfp)
{
#ifdef CONFIG_DEBUG_BLK_CGROUP
if (blkg_rwstat_init(&stats->merged, gfp) ||
blkg_rwstat_init(&stats->service_time, gfp) ||
blkg_rwstat_init(&stats->wait_time, gfp) ||
@ -371,6 +396,7 @@ static int bfqg_stats_init(struct bfqg_stats *stats, gfp_t gfp)
bfqg_stats_exit(stats);
return -ENOMEM;
}
#endif
return 0;
}
@ -887,6 +913,7 @@ static ssize_t bfq_io_set_weight(struct kernfs_open_file *of,
return bfq_io_set_weight_legacy(of_css(of), NULL, weight);
}
#ifdef CONFIG_DEBUG_BLK_CGROUP
static int bfqg_print_stat(struct seq_file *sf, void *v)
{
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), blkg_prfill_stat,
@ -991,6 +1018,7 @@ static int bfqg_print_avg_queue_size(struct seq_file *sf, void *v)
0, false);
return 0;
}
#endif /* CONFIG_DEBUG_BLK_CGROUP */
struct bfq_group *bfq_create_group_hierarchy(struct bfq_data *bfqd, int node)
{
@ -1028,15 +1056,6 @@ struct cftype bfq_blkcg_legacy_files[] = {
},
/* statistics, covers only the tasks in the bfqg */
{
.name = "bfq.time",
.private = offsetof(struct bfq_group, stats.time),
.seq_show = bfqg_print_stat,
},
{
.name = "bfq.sectors",
.seq_show = bfqg_print_stat_sectors,
},
{
.name = "bfq.io_service_bytes",
.private = (unsigned long)&blkcg_policy_bfq,
@ -1047,6 +1066,16 @@ struct cftype bfq_blkcg_legacy_files[] = {
.private = (unsigned long)&blkcg_policy_bfq,
.seq_show = blkg_print_stat_ios,
},
#ifdef CONFIG_DEBUG_BLK_CGROUP
{
.name = "bfq.time",
.private = offsetof(struct bfq_group, stats.time),
.seq_show = bfqg_print_stat,
},
{
.name = "bfq.sectors",
.seq_show = bfqg_print_stat_sectors,
},
{
.name = "bfq.io_service_time",
.private = offsetof(struct bfq_group, stats.service_time),
@ -1067,17 +1096,9 @@ struct cftype bfq_blkcg_legacy_files[] = {
.private = offsetof(struct bfq_group, stats.queued),
.seq_show = bfqg_print_rwstat,
},
#endif /* CONFIG_DEBUG_BLK_CGROUP */
/* the same statictics which cover the bfqg and its descendants */
{
.name = "bfq.time_recursive",
.private = offsetof(struct bfq_group, stats.time),
.seq_show = bfqg_print_stat_recursive,
},
{
.name = "bfq.sectors_recursive",
.seq_show = bfqg_print_stat_sectors_recursive,
},
{
.name = "bfq.io_service_bytes_recursive",
.private = (unsigned long)&blkcg_policy_bfq,
@ -1088,6 +1109,16 @@ struct cftype bfq_blkcg_legacy_files[] = {
.private = (unsigned long)&blkcg_policy_bfq,
.seq_show = blkg_print_stat_ios_recursive,
},
#ifdef CONFIG_DEBUG_BLK_CGROUP
{
.name = "bfq.time_recursive",
.private = offsetof(struct bfq_group, stats.time),
.seq_show = bfqg_print_stat_recursive,
},
{
.name = "bfq.sectors_recursive",
.seq_show = bfqg_print_stat_sectors_recursive,
},
{
.name = "bfq.io_service_time_recursive",
.private = offsetof(struct bfq_group, stats.service_time),
@ -1132,6 +1163,7 @@ struct cftype bfq_blkcg_legacy_files[] = {
.private = offsetof(struct bfq_group, stats.dequeue),
.seq_show = bfqg_print_stat,
},
#endif /* CONFIG_DEBUG_BLK_CGROUP */
{ } /* terminate */
};
@ -1147,18 +1179,6 @@ struct cftype bfq_blkg_files[] = {
#else /* CONFIG_BFQ_GROUP_IOSCHED */
void bfqg_stats_update_io_add(struct bfq_group *bfqg, struct bfq_queue *bfqq,
unsigned int op) { }
void bfqg_stats_update_io_remove(struct bfq_group *bfqg, unsigned int op) { }
void bfqg_stats_update_io_merged(struct bfq_group *bfqg, unsigned int op) { }
void bfqg_stats_update_completion(struct bfq_group *bfqg, uint64_t start_time,
uint64_t io_start_time, unsigned int op) { }
void bfqg_stats_update_dequeue(struct bfq_group *bfqg) { }
void bfqg_stats_set_start_empty_time(struct bfq_group *bfqg) { }
void bfqg_stats_update_idle_time(struct bfq_group *bfqg) { }
void bfqg_stats_set_start_idle_time(struct bfq_group *bfqg) { }
void bfqg_stats_update_avg_queue_size(struct bfq_group *bfqg) { }
void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
struct bfq_group *bfqg) {}

14
block/bfq-iosched.c
View file

@ -3693,14 +3693,14 @@ static struct request *bfq_dispatch_request(struct blk_mq_hw_ctx *hctx)
{
struct bfq_data *bfqd = hctx->queue->elevator->elevator_data;
struct request *rq;
#ifdef CONFIG_BFQ_GROUP_IOSCHED
#if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP)
struct bfq_queue *in_serv_queue, *bfqq;
bool waiting_rq, idle_timer_disabled;
#endif
spin_lock_irq(&bfqd->lock);
#ifdef CONFIG_BFQ_GROUP_IOSCHED
#if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP)
in_serv_queue = bfqd->in_service_queue;
waiting_rq = in_serv_queue && bfq_bfqq_wait_request(in_serv_queue);
@ -3714,7 +3714,7 @@ static struct request *bfq_dispatch_request(struct blk_mq_hw_ctx *hctx)
#endif
spin_unlock_irq(&bfqd->lock);
#ifdef CONFIG_BFQ_GROUP_IOSCHED
#if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP)
bfqq = rq ? RQ_BFQQ(rq) : NULL;
if (!idle_timer_disabled && !bfqq)
return rq;
@ -4281,7 +4281,7 @@ static void bfq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
{
struct request_queue *q = hctx->queue;
struct bfq_data *bfqd = q->elevator->elevator_data;
#ifdef CONFIG_BFQ_GROUP_IOSCHED
#if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP)
struct bfq_queue *bfqq = RQ_BFQQ(rq);
bool idle_timer_disabled = false;
unsigned int cmd_flags;
@ -4304,7 +4304,7 @@ static void bfq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
else
list_add_tail(&rq->queuelist, &bfqd->dispatch);
} else {
#ifdef CONFIG_BFQ_GROUP_IOSCHED
#if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP)
idle_timer_disabled = __bfq_insert_request(bfqd, rq);
/*
* Update bfqq, because, if a queue merge has occurred
@ -4323,7 +4323,7 @@ static void bfq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
}
}
#ifdef CONFIG_BFQ_GROUP_IOSCHED
#if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP)
/*
* Cache cmd_flags before releasing scheduler lock, because rq
* may disappear afterwards (for example, because of a request
@ -4333,7 +4333,7 @@ static void bfq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
#endif
spin_unlock_irq(&bfqd->lock);
#ifdef CONFIG_BFQ_GROUP_IOSCHED
#if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP)
if (!bfqq)
return;
/*

4
block/bfq-iosched.h
View file

@ -689,7 +689,7 @@ enum bfqq_expiration {
};
struct bfqg_stats {
#ifdef CONFIG_BFQ_GROUP_IOSCHED
#if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP)
/* number of ios merged */
struct blkg_rwstat merged;
/* total time spent on device in ns, may not be accurate w/ queueing */
@ -717,7 +717,7 @@ struct bfqg_stats {
uint64_t start_idle_time;
uint64_t start_empty_time;
uint16_t flags;
#endif /* CONFIG_BFQ_GROUP_IOSCHED */
#endif /* CONFIG_BFQ_GROUP_IOSCHED && CONFIG_DEBUG_BLK_CGROUP */
};
#ifdef CONFIG_BFQ_GROUP_IOSCHED