From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from esa5.hgst.iphmx.com ([216.71.153.144]:6956 "EHLO esa5.hgst.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751329AbdGaXBM (ORCPT ); Mon, 31 Jul 2017 19:01:12 -0400 From: Bart Van Assche To: "hch@infradead.org" , "linux-block@vger.kernel.org" , "axboe@fb.com" , "ming.lei@redhat.com" CC: Bart Van Assche , "linux-scsi@vger.kernel.org" , "jejb@linux.vnet.ibm.com" , "martin.petersen@oracle.com" Subject: Re: [PATCH 01/14] blk-mq-sched: fix scheduler bad performance Date: Mon, 31 Jul 2017 23:00:24 +0000 Message-ID: <1501542023.2466.22.camel@wdc.com> References: <20170731165111.11536-1-ming.lei@redhat.com> <20170731165111.11536-3-ming.lei@redhat.com> In-Reply-To: <20170731165111.11536-3-ming.lei@redhat.com> Content-Type: text/plain; charset="iso-8859-1" MIME-Version: 1.0 Sender: linux-block-owner@vger.kernel.org List-Id: linux-block@vger.kernel.org On Tue, 2017-08-01 at 00:50 +0800, Ming Lei wrote: > 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 > --- > block/blk-mq-sched.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) >=20 > diff --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= ; > - 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) > */ > 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 Bart.=