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block/mq-deadline: Track I/O statistics 

Track I/O statistics per I/O priority and export these statistics to
debugfs. These statistics help developers of the deadline scheduler.

Cc: Damien Le Moal <damien.lemoal@wdc.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Cc: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20210618004456.7280-15-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Bart Van Assche 2021-06-17 17:44:54 -07:00 committed by Jens Axboe
parent c807ab520f
commit 38ba64d12d
1 changed files with 100 additions and 0 deletions
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100
block/mq-deadline.c
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@ -51,6 +51,19 @@ enum dd_prio {
enum { DD_PRIO_COUNT = 3 };
/* I/O statistics per I/O priority. */
struct io_stats_per_prio {
local_t inserted;
local_t merged;
local_t dispatched;
local_t completed;
};
/* I/O statistics for all I/O priorities (enum dd_prio). */
struct io_stats {
struct io_stats_per_prio stats[DD_PRIO_COUNT];
};
/*
* Deadline scheduler data per I/O priority (enum dd_prio). Requests are
* present on both sort_list[] and fifo_list[].
@ -75,6 +88,8 @@ struct deadline_data {
unsigned int batching; /* number of sequential requests made */
unsigned int starved; /* times reads have starved writes */
struct io_stats __percpu *stats;
/*
* settings that change how the i/o scheduler behaves
*/
@ -88,6 +103,33 @@ struct deadline_data {
spinlock_t zone_lock;
};
/* Count one event of type 'event_type' and with I/O priority 'prio' */
#define dd_count(dd, event_type, prio) do { \
struct io_stats *io_stats = get_cpu_ptr((dd)->stats); \
\
BUILD_BUG_ON(!__same_type((dd), struct deadline_data *)); \
BUILD_BUG_ON(!__same_type((prio), enum dd_prio)); \
local_inc(&io_stats->stats[(prio)].event_type); \
put_cpu_ptr(io_stats); \
} while (0)
/*
* Returns the total number of dd_count(dd, event_type, prio) calls across all
* CPUs. No locking or barriers since it is fine if the returned sum is slightly
* outdated.
*/
#define dd_sum(dd, event_type, prio) ({ \
unsigned int cpu; \
u32 sum = 0; \
\
BUILD_BUG_ON(!__same_type((dd), struct deadline_data *)); \
BUILD_BUG_ON(!__same_type((prio), enum dd_prio)); \
for_each_present_cpu(cpu) \
sum += local_read(&per_cpu_ptr((dd)->stats, cpu)-> \
stats[(prio)].event_type); \
sum; \
})
/* Maps an I/O priority class to a deadline scheduler priority. */
static const enum dd_prio ioprio_class_to_prio[] = {
[IOPRIO_CLASS_NONE] = DD_BE_PRIO,
@ -187,9 +229,12 @@ static void dd_request_merged(struct request_queue *q, struct request *req,
static void dd_merged_requests(struct request_queue *q, struct request *req,
struct request *next)
{
struct deadline_data *dd = q->elevator->elevator_data;
const u8 ioprio_class = dd_rq_ioclass(next);
const enum dd_prio prio = ioprio_class_to_prio[ioprio_class];
dd_count(dd, merged, prio);
/*
* if next expires before rq, assign its expire time to rq
* and move into next position (next will be deleted) in fifo
@ -225,6 +270,12 @@ deadline_move_request(struct deadline_data *dd, struct dd_per_prio *per_prio,
deadline_remove_request(rq->q, per_prio, rq);
}
/* Number of requests queued for a given priority level. */
static u32 dd_queued(struct deadline_data *dd, enum dd_prio prio)
{
return dd_sum(dd, inserted, prio) - dd_sum(dd, completed, prio);
}
/*
* deadline_check_fifo returns 0 if there are no expired requests on the fifo,
* 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
@ -319,6 +370,8 @@ static struct request *__dd_dispatch_request(struct deadline_data *dd,
{
struct request *rq, *next_rq;
enum dd_data_dir data_dir;
enum dd_prio prio;
u8 ioprio_class;
lockdep_assert_held(&dd->lock);
@ -408,6 +461,9 @@ dispatch_request:
dd->batching++;
deadline_move_request(dd, per_prio, rq);
done:
ioprio_class = dd_rq_ioclass(rq);
prio = ioprio_class_to_prio[ioprio_class];
dd_count(dd, dispatched, prio);
/*
* If the request needs its target zone locked, do it.
*/
@ -491,6 +547,8 @@ static void dd_exit_sched(struct elevator_queue *e)
WARN_ON_ONCE(!list_empty(&per_prio->fifo_list[DD_WRITE]));
}
free_percpu(dd->stats);
kfree(dd);
}
@ -514,6 +572,11 @@ static int dd_init_sched(struct request_queue *q, struct elevator_type *e)
eq->elevator_data = dd;
dd->stats = alloc_percpu_gfp(typeof(*dd->stats),
GFP_KERNEL | __GFP_ZERO);
if (!dd->stats)
goto free_dd;
for (prio = 0; prio <= DD_PRIO_MAX; prio++) {
struct dd_per_prio *per_prio = &dd->per_prio[prio];
@ -535,6 +598,9 @@ static int dd_init_sched(struct request_queue *q, struct elevator_type *e)
q->elevator = eq;
return 0;
free_dd:
kfree(dd);
put_eq:
kobject_put(&eq->kobj);
return ret;
@ -614,6 +680,7 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
blk_req_zone_write_unlock(rq);
prio = ioprio_class_to_prio[ioprio_class];
dd_count(dd, inserted, prio);
if (blk_mq_sched_try_insert_merge(q, rq))
return;
@ -692,6 +759,8 @@ static void dd_finish_request(struct request *rq)
const enum dd_prio prio = ioprio_class_to_prio[ioprio_class];
struct dd_per_prio *per_prio = &dd->per_prio[prio];
dd_count(dd, completed, prio);
if (blk_queue_is_zoned(q)) {
unsigned long flags;
@ -873,6 +942,35 @@ static int dd_async_depth_show(void *data, struct seq_file *m)
return 0;
}
static int dd_queued_show(void *data, struct seq_file *m)
{
struct request_queue *q = data;
struct deadline_data *dd = q->elevator->elevator_data;
seq_printf(m, "%u %u %u\n", dd_queued(dd, DD_RT_PRIO),
dd_queued(dd, DD_BE_PRIO),
dd_queued(dd, DD_IDLE_PRIO));
return 0;
}
/* Number of requests owned by the block driver for a given priority. */
static u32 dd_owned_by_driver(struct deadline_data *dd, enum dd_prio prio)
{
return dd_sum(dd, dispatched, prio) + dd_sum(dd, merged, prio)
- dd_sum(dd, completed, prio);
}
static int dd_owned_by_driver_show(void *data, struct seq_file *m)
{
struct request_queue *q = data;
struct deadline_data *dd = q->elevator->elevator_data;
seq_printf(m, "%u %u %u\n", dd_owned_by_driver(dd, DD_RT_PRIO),
dd_owned_by_driver(dd, DD_BE_PRIO),
dd_owned_by_driver(dd, DD_IDLE_PRIO));
return 0;
}
#define DEADLINE_DISPATCH_ATTR(prio) \
static void *deadline_dispatch##prio##_start(struct seq_file *m, \
loff_t *pos) \
@ -941,6 +1039,8 @@ static const struct blk_mq_debugfs_attr deadline_queue_debugfs_attrs[] = {
{"dispatch0", 0400, .seq_ops = &deadline_dispatch0_seq_ops},
{"dispatch1", 0400, .seq_ops = &deadline_dispatch1_seq_ops},
{"dispatch2", 0400, .seq_ops = &deadline_dispatch2_seq_ops},
{"owned_by_driver", 0400, dd_owned_by_driver_show},
{"queued", 0400, dd_queued_show},
{},
};
#undef DEADLINE_QUEUE_DDIR_ATTRS