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block: only allocate poll_stats if there's a user of them 

This is essentially never used, yet it's about 1/3rd of the total
queue size. Allocate it when needed, and don't embed it in the queue.

Kill the queue flag for this while at it, since we can just check the
assigned pointer now.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2021-11-13 14:03:26 -07:00
parent 25c4b5e058
commit 48b5c1fbcd
6 changed files with 26 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
block/blk-mq-debugfs.c
View File

@ -122,7 +122,6 @@ static const char *const blk_queue_flag_name[] = {
QUEUE_FLAG_NAME(FUA),
QUEUE_FLAG_NAME(DAX),
QUEUE_FLAG_NAME(STATS),
QUEUE_FLAG_NAME(POLL_STATS),
QUEUE_FLAG_NAME(REGISTERED),
QUEUE_FLAG_NAME(QUIESCED),
QUEUE_FLAG_NAME(PCI_P2PDMA),

10
block/blk-mq.c
View File

@ -4581,11 +4581,10 @@ EXPORT_SYMBOL_GPL(blk_mq_update_nr_hw_queues);
/* Enable polling stats and return whether they were already enabled. */
static bool blk_poll_stats_enable(struct request_queue *q)
{
if (test_bit(QUEUE_FLAG_POLL_STATS, &q->queue_flags) ||
blk_queue_flag_test_and_set(QUEUE_FLAG_POLL_STATS, q))
if (q->poll_stat)
return true;
blk_stat_add_callback(q, q->poll_cb);
return false;
return blk_stats_alloc_enable(q);
}
static void blk_mq_poll_stats_start(struct request_queue *q)
@ -4594,8 +4593,7 @@ static void blk_mq_poll_stats_start(struct request_queue *q)
* We don't arm the callback if polling stats are not enabled or the
* callback is already active.
*/
if (!test_bit(QUEUE_FLAG_POLL_STATS, &q->queue_flags) ||
blk_stat_is_active(q->poll_cb))
if (!q->poll_stat || blk_stat_is_active(q->poll_cb))
return;
blk_stat_activate_msecs(q->poll_cb, 100);

18
block/blk-stat.c
View File

@ -219,3 +219,21 @@ void blk_free_queue_stats(struct blk_queue_stats *stats)
kfree(stats);
}
bool blk_stats_alloc_enable(struct request_queue *q)
{
struct blk_rq_stat *poll_stat;
poll_stat = kcalloc(BLK_MQ_POLL_STATS_BKTS, sizeof(*poll_stat),
GFP_ATOMIC);
if (!poll_stat)
return false;
if (cmpxchg(&q->poll_stat, NULL, poll_stat) != NULL) {
kfree(poll_stat);
return true;
}
blk_stat_add_callback(q, q->poll_cb);
return false;
}

1
block/blk-stat.h
View File

@ -64,6 +64,7 @@ struct blk_stat_callback {
struct blk_queue_stats *blk_alloc_queue_stats(void);
void blk_free_queue_stats(struct blk_queue_stats *);
bool blk_stats_alloc_enable(struct request_queue *q);
void blk_stat_add(struct request *rq, u64 now);

3
block/blk-sysfs.c
View File

@ -785,11 +785,12 @@ static void blk_release_queue(struct kobject *kobj)
might_sleep();
if (test_bit(QUEUE_FLAG_POLL_STATS, &q->queue_flags))
if (q->poll_stat)
blk_stat_remove_callback(q, q->poll_cb);
blk_stat_free_callback(q->poll_cb);
blk_free_queue_stats(q->stats);
kfree(q->poll_stat);
blk_exit_queue(q);

3
include/linux/blkdev.h
View File

@ -267,7 +267,7 @@ struct request_queue {
int poll_nsec;
struct blk_stat_callback *poll_cb;
struct blk_rq_stat poll_stat[BLK_MQ_POLL_STATS_BKTS];
struct blk_rq_stat *poll_stat;
struct timer_list timeout;
struct work_struct timeout_work;
@ -397,7 +397,6 @@ struct request_queue {
#define QUEUE_FLAG_FUA 18 /* device supports FUA writes */
#define QUEUE_FLAG_DAX 19 /* device supports DAX */
#define QUEUE_FLAG_STATS 20 /* track IO start and completion times */
#define QUEUE_FLAG_POLL_STATS 21 /* collecting stats for hybrid polling */
#define QUEUE_FLAG_REGISTERED 22 /* queue has been registered to a disk */
#define QUEUE_FLAG_QUIESCED 24 /* queue has been quiesced */
#define QUEUE_FLAG_PCI_P2PDMA 25 /* device supports PCI p2p requests */