From: Paolo Valente <paolo.valente@linaro.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
ulf.hansson@linaro.org, linus.walleij@linaro.org,
broonie@kernel.org, bfq-iosched@googlegroups.com,
oleksandr@natalenko.name, mancha@tower-research.com,
Paolo Valente <paolo.valente@linaro.org>
Subject: [PATCH BUGFIX IMPROVEMENT 11/14] block, bfq: reduce threshold for detecting command queueing
Date: Tue, 29 Jan 2019 12:06:35 +0100 [thread overview]
Message-ID: <20190129110638.12652-12-paolo.valente@linaro.org> (raw)
In-Reply-To: <20190129110638.12652-1-paolo.valente@linaro.org>
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@linaro.org>
---
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
next prev parent reply other threads:[~2019-01-29 11:07 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-29 11:06 [PATCH BUGFIX IMPROVEMENT 00/14] batch of patches for next linux release Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 01/14] block, bfq: do not consider interactive queues in srt filtering Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 02/14] block, bfq: avoid selecting a queue w/o budget Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 03/14] block, bfq: make sure queue budgets are not below service received Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 04/14] block, bfq: remove case of redirected bic from insert_request Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 05/14] block, bfq: consider also ioprio classes in symmetry detection Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 06/14] block, bfq: split function bfq_better_to_idle Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 07/14] block, bfq: do not plug I/O of in-service queue when harmful Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 08/14] block, bfq: unconditionally plug I/O in asymmetric scenarios Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 09/14] block, bfq: fix sequential rq detection in rate estimation Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 10/14] block, bfq: fix queue removal from weights tree Paolo Valente
2019-01-29 11:06 ` Paolo Valente [this message]
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 12/14] block, bfq: port commit "cfq-iosched: improve hw_tag detection" Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 13/14] block, bfq: do not overcharge writes in asymmetric scenarios Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 14/14] block, bfq: fix in-service-queue check for queue merging Paolo Valente
2019-01-31 19:50 ` [PATCH BUGFIX IMPROVEMENT 00/14] batch of patches for next linux release Jens Axboe
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