Re: [PATCH 3/3] block: only allocate poll_stats if there's a user of them
From: Jens Axboe <axboe@kernel.dk>
Date: 2021-11-23 16:45:43
Subsystem:
block layer, the rest · Maintainers:
Jens Axboe, Linus Torvalds
On 11/23/21 9:41 AM, Christoph Hellwig wrote:
On Tue, Nov 23, 2021 at 09:18:13AM -0700, Jens Axboe wrote:quoted
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. Signed-off-by: Jens Axboe <axboe@kernel.dk> --- block/blk-mq.c | 20 ++++++++++++++++++-- block/blk-stat.c | 6 ------ block/blk-sysfs.c | 1 + include/linux/blkdev.h | 9 +++++++-- 4 files changed, 26 insertions(+), 10 deletions(-)diff --git a/block/blk-mq.c b/block/blk-mq.c index 20a6445f6a01..cb41c441aa8f 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c@@ -4577,9 +4577,25 @@ 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)) + struct blk_rq_stat *poll_stat; + + if (test_bit(QUEUE_FLAG_POLL_STATS, &q->queue_flags)) return true;Can't we replace the checks for QUEUE_FLAG_POLL_STATS with checks for q->poll_stat now?
I think so:
diff --git a/block/blk-mq.c b/block/blk-mq.c
index f011fa3ebcc7..af4580bdf931 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c@@ -4593,7 +4593,7 @@ static bool blk_poll_stats_enable(struct request_queue *q) { struct blk_rq_stat *poll_stat; - if (test_bit(QUEUE_FLAG_POLL_STATS, &q->queue_flags)) + if (q->poll_stat) return true; poll_stat = kzalloc(BLK_MQ_POLL_STATS_BKTS * sizeof(*poll_stat),
@@ -4602,7 +4602,7 @@ static bool blk_poll_stats_enable(struct request_queue *q) return false; spin_lock_irq(&q->stats->lock); - if (blk_queue_flag_test_and_set(QUEUE_FLAG_POLL_STATS, q)) { + if (q->poll_stat) { spin_unlock_irq(&q->stats->lock); kfree(poll_stat); return true;
@@ -4620,8 +4620,7 @@ 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);
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index e1b846ec58cb..c079be1c58a3 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c@@ -785,7 +785,7 @@ 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);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 3d558cb397d5..20cf877d6627 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h@@ -414,7 +414,6 @@ 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 */
--
Jens Axboe