[PATCH for-6.18/block 03/16] blk-mq: add QUEUE_FLAG_BIO_ISSUE_TIME

Yu Kuai
2025-09-05T07:15:55Z

From: Yu Kuai <yukuai3@huawei.com>

bio->issue_time_ns is initialized for every bio, however, it's only used
by blk-iolatency. Add a new queue_flag and only set this flag when
blk-iolatency is enabled, so that extra blk_time_get_ns() can be saved
for disks that blk-iolatency is not enabled.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
---
block/blk-iolatency.c | 5 +++++
block/blk-mq-debugfs.c | 1 +
block/blk-mq.c | 4 +++-
include/linux/blkdev.h | 1 +
4 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c
index 554b191a6892..45bd18f68541 100644
--- a/block/blk-iolatency.c
+++ b/block/blk-iolatency.c
@@ -742,10 +742,15 @@ static void blkiolatency_enable_work_fn(struct work_struct *work)
*/
enabled = atomic_read(&blkiolat->enable_cnt);
if (enabled != blkiolat->enabled) {
+ struct request_queue *q = blkiolat->rqos.disk->queue;
unsigned int memflags;

memflags = blk_mq_freeze_queue(blkiolat->rqos.disk->queue);
blkiolat->enabled = enabled;
+ if (enabled)
+ blk_queue_flag_set(QUEUE_FLAG_BIO_ISSUE_TIME, q);
+ else
+ blk_queue_flag_clear(QUEUE_FLAG_BIO_ISSUE_TIME, q);
blk_mq_unfreeze_queue(blkiolat->rqos.disk->queue, memflags);
}
}
diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index 32c65efdda46..4896525b1c05 100644
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -96,6 +96,7 @@ static const char *const blk_queue_flag_name[] = {
QUEUE_FLAG_NAME(DISABLE_WBT_DEF),
QUEUE_FLAG_NAME(NO_ELV_SWITCH),
QUEUE_FLAG_NAME(QOS_ENABLED),
+ QUEUE_FLAG_NAME(BIO_ISSUE_TIME),
};
#undef QUEUE_FLAG_NAME

diff --git a/block/blk-mq.c b/block/blk-mq.c
index d2538683c83d..eaa18536333f 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3168,7 +3168,9 @@ void blk_mq_submit_bio(struct bio *bio)
if (!bio_integrity_prep(bio))
goto queue_exit;

- bio->issue_time_ns = blk_time_get_ns();
+ if (test_bit(QUEUE_FLAG_BIO_ISSUE_TIME, &q->queue_flags))
+ bio->issue_time_ns = blk_time_get_ns();
+
if (blk_mq_attempt_bio_merge(q, bio, nr_segs))
goto queue_exit;

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 7709d55adc23..3c3b64684d14 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -657,6 +657,7 @@ enum {
QUEUE_FLAG_DISABLE_WBT_DEF, /* for sched to disable/enable wbt */
QUEUE_FLAG_NO_ELV_SWITCH, /* can't switch elevator any more */
QUEUE_FLAG_QOS_ENABLED, /* qos is enabled */
+ QUEUE_FLAG_BIO_ISSUE_TIME, /* record bio->issue_time_ns */
QUEUE_FLAG_MAX
};

--
2.39.2