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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: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20211125133645.27483-7-jack@suse.cz
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jan Kara 2021-11-25 14:36:40 +01:00 committed by Jens Axboe
parent 582f04e19a
commit 1eb17f5e15
1 changed files with 8 additions and 0 deletions
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8
block/bfq-iosched.c
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@ -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