bfq borrowed from cfq a simple heuristic for detecting whether the drive performs command queueing: check whether the average number of in-flight requests is above a given threshold. Unfortunately this heuristic does fail to detect queueing (on drives with queueing) if processes doing I/O are few and issue I/O with a low depth. To reduce false negatives, this commit lowers the threshold. Signed-off-by: Paolo Valente <paolo.valente@xxxxxxxxxx> --- block/bfq-iosched.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index bf585ad29bb5..48b579032d14 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -230,7 +230,7 @@ static struct kmem_cache *bfq_pool; #define BFQ_MIN_TT (2 * NSEC_PER_MSEC) /* hw_tag detection: parallel requests threshold and min samples needed. */ -#define BFQ_HW_QUEUE_THRESHOLD 4 +#define BFQ_HW_QUEUE_THRESHOLD 3 #define BFQ_HW_QUEUE_SAMPLES 32 #define BFQQ_SEEK_THR (sector_t)(8 * 100) @@ -4798,7 +4798,7 @@ static void bfq_update_hw_tag(struct bfq_data *bfqd) * sum is not exact, as it's not taking into account deactivated * requests. */ - if (bfqd->rq_in_driver + bfqd->queued < BFQ_HW_QUEUE_THRESHOLD) + if (bfqd->rq_in_driver + bfqd->queued <= BFQ_HW_QUEUE_THRESHOLD) return; if (bfqd->hw_tag_samples++ < BFQ_HW_QUEUE_SAMPLES) -- 2.20.1
