Commit 1eb17f5e authored by Jan Kara's avatar Jan Kara Committed by Jens Axboe
Browse files

bfq: Log waker detections 



Waker - wakee relationships are important in deciding whether one queue
can preempt the other one. Print information about detected waker-wakee
relationships so that scheduling decisions can be better understood from
block traces.

Acked-by: default avatarPaolo Valente <paolo.valente@linaro.org>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20211125133645.27483-7-jack@suse.cz


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 582f04e1

block/bfq-iosched.c

+8 −0
Original line number Diff line number Diff line
@@ -2127,6 +2127,8 @@ static void bfq_update_io_intensity(struct bfq_queue *bfqq, u64 now_ns) 
static void bfq_check_waker(struct bfq_data *bfqd, struct bfq_queue *bfqq,

			    u64 now_ns)

{

	char waker_name[MAX_BFQQ_NAME_LENGTH];



	if (!bfqd->last_completed_rq_bfqq ||

	    bfqd->last_completed_rq_bfqq == bfqq ||

	    bfq_bfqq_has_short_ttime(bfqq) ||
@@ -2154,12 +2156,18 @@ static void bfq_check_waker(struct bfq_data *bfqd, struct bfq_queue *bfqq, 
			bfqd->last_completed_rq_bfqq;

		bfqq->num_waker_detections = 1;

		bfqq->waker_detection_started = now_ns;

		bfq_bfqq_name(bfqq->tentative_waker_bfqq, waker_name,

			      MAX_BFQQ_NAME_LENGTH);

		bfq_log_bfqq(bfqd, bfqq, "set tenative waker %s", waker_name);

	} else /* Same tentative waker queue detected again */

		bfqq->num_waker_detections++;



	if (bfqq->num_waker_detections == 3) {

		bfqq->waker_bfqq = bfqd->last_completed_rq_bfqq;

		bfqq->tentative_waker_bfqq = NULL;

		bfq_bfqq_name(bfqq->waker_bfqq, waker_name,

			      MAX_BFQQ_NAME_LENGTH);

		bfq_log_bfqq(bfqd, bfqq, "set waker %s", waker_name);



		/*

		 * If the waker queue disappears, then