Re: [PATCH 01/14] blk-mq-sched: fix scheduler bad performance
From: Bart Van Assche <hidden>
Date: 2017-07-31 23:01:12
Also in:
linux-scsi
On Tue, 2017-08-01 at 00:50 +0800, Ming Lei wrote:
quoted hunk ↗ jump to hunk
When hw queue is busy, we shouldn't take requests from scheduler queue any more, otherwise IO merge will be difficult to do. =20 This patch fixes the awful IO performance on some SCSI devices(lpfc, qla2xxx, ...) when mq-deadline/kyber is used by not taking requests if hw queue is busy. =20 Signed-off-by: Ming Lei <redacted> --- block/blk-mq-sched.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) =20diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c index 4ab69435708c..47a25333a136 100644 --- a/block/blk-mq-sched.c +++ b/block/blk-mq-sched.c@@ -94,7 +94,7 @@ void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ct=
x *hctx)
struct request_queue *q =3D hctx->queue; struct elevator_queue *e =3D q->elevator; const bool has_sched_dispatch =3D e && e->type->ops.mq.dispatch_request=
;
quoted hunk ↗ jump to hunk
- bool did_work =3D false; + bool can_go =3D true; LIST_HEAD(rq_list); =20 /* RCU or SRCU read lock is needed before checking quiesced flag */@@ -125,7 +125,7 @@ void blk_mq_sched_dispatch_requests(struct blk_mq_hw_=
ctx *hctx)
quoted hunk ↗ jump to hunk
*/ if (!list_empty(&rq_list)) { blk_mq_sched_mark_restart_hctx(hctx); - did_work =3D blk_mq_dispatch_rq_list(q, &rq_list); + can_go =3D blk_mq_dispatch_rq_list(q, &rq_list); } else if (!has_sched_dispatch) { blk_mq_flush_busy_ctxs(hctx, &rq_list); blk_mq_dispatch_rq_list(q, &rq_list);@@ -136,7 +136,7 @@ void blk_mq_sched_dispatch_requests(struct blk_mq_hw_=
ctx *hctx)
* on the dispatch list, OR if we did have work but weren't able
* to make progress.
*/
- if (!did_work && has_sched_dispatch) {
+ if (can_go && has_sched_dispatch) {
do {
struct request *rq;Hello Ming, Please chose a better name for the new variable, e.g. "do_sched_dispatch".= =20 Otherwise this patch looks fine to me. Hence: Reviewed-by: Bart Van Assche <redacted> Bart.=