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| author | Paolo Valente <paolo.valente@linaro.org> | 2019-01-29 12:06:35 +0100 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2019-01-31 12:50:24 -0700 |
| commit | a3c92560324bd616deaecb6842b2a0337a80ad8b (patch) | |
| tree | 7cf2e0a7b0e83f82d4faf9dd8d0762795303d68c /block/bfq-iosched.c | |
| parent | 9dee8b3b057e1da26f85f1842f2aaf3bb200fb94 (diff) | |
| download | lwn-a3c92560324bd616deaecb6842b2a0337a80ad8b.tar.gz lwn-a3c92560324bd616deaecb6842b2a0337a80ad8b.zip | |
block, bfq: reduce threshold for detecting command queueing
bfq simple heuristic from cfq 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@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/bfq-iosched.c')
| -rw-r--r-- | block/bfq-iosched.c | 4 |
1 files 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) |