From patchwork Mon Oct 9 11:24:23 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ming Lei X-Patchwork-Id: 9992653 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id A8D7360244 for ; Mon, 9 Oct 2017 11:25:28 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9AECF28797 for ; Mon, 9 Oct 2017 11:25:28 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 8FC70287A3; Mon, 9 Oct 2017 11:25:28 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 0E7E328797 for ; Mon, 9 Oct 2017 11:25:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754159AbdJILZB (ORCPT ); Mon, 9 Oct 2017 07:25:01 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42956 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754107AbdJILY7 (ORCPT ); Mon, 9 Oct 2017 07:24:59 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E2A385D68C; Mon, 9 Oct 2017 11:24:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com E2A385D68C Authentication-Results: ext-mx10.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx10.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=ming.lei@redhat.com Received: from localhost (ovpn-12-144.pek2.redhat.com [10.72.12.144]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7C3166060A; Mon, 9 Oct 2017 11:24:52 +0000 (UTC) From: Ming Lei To: Jens Axboe , linux-block@vger.kernel.org, Christoph Hellwig , Mike Snitzer , dm-devel@redhat.com Cc: Bart Van Assche , Laurence Oberman , Paolo Valente , Oleksandr Natalenko , Tom Nguyen , linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, Omar Sandoval , Ming Lei Subject: [PATCH V6 4/5] blk-mq-sched: improve dispatching from sw queue Date: Mon, 9 Oct 2017 19:24:23 +0800 Message-Id: <20171009112424.30524-5-ming.lei@redhat.com> In-Reply-To: <20171009112424.30524-1-ming.lei@redhat.com> References: <20171009112424.30524-1-ming.lei@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Mon, 09 Oct 2017 11:24:59 +0000 (UTC) Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP SCSI devices use host-wide tagset, and the shared driver tag space is often quite big. Meantime there is also queue depth for each lun( .cmd_per_lun), which is often small, for example, on both lpfc and qla2xxx, .cmd_per_lun is just 3. So lots of requests may stay in sw queue, and we always flush all belonging to same hw queue and dispatch them all to driver, unfortunately it is easy to cause queue busy because of the small .cmd_per_lun. Once these requests are flushed out, they have to stay in hctx->dispatch, and no bio merge can participate into these requests, and sequential IO performance is hurt a lot. This patch introduces blk_mq_dequeue_from_ctx for dequeuing request from sw queue so that we can dispatch them in scheduler's way, then we can avoid to dequeue too many requests from sw queue when ->dispatch isn't flushed completely. This patch improves dispatching from sw queue when there is per-request-queue queue depth by taking request one by one from sw queue, just like the way of IO scheduler. Reviewed-by: Omar Sandoval Reviewed-by: Bart Van Assche Signed-off-by: Ming Lei --- block/blk-mq-sched.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++-- block/blk-mq.c | 39 +++++++++++++++++++++++++++++++++++++++ block/blk-mq.h | 2 ++ include/linux/blk-mq.h | 2 ++ 4 files changed, 91 insertions(+), 2 deletions(-) diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c index be29ba849408..14b354f617e5 100644 --- a/block/blk-mq-sched.c +++ b/block/blk-mq-sched.c @@ -104,6 +104,39 @@ static void blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx) } while (blk_mq_dispatch_rq_list(q, &rq_list)); } +static struct blk_mq_ctx *blk_mq_next_ctx(struct blk_mq_hw_ctx *hctx, + struct blk_mq_ctx *ctx) +{ + unsigned idx = ctx->index_hw; + + if (++idx == hctx->nr_ctx) + idx = 0; + + return hctx->ctxs[idx]; +} + +static void blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx) +{ + struct request_queue *q = hctx->queue; + LIST_HEAD(rq_list); + struct blk_mq_ctx *ctx = READ_ONCE(hctx->dispatch_from); + + do { + struct request *rq; + + rq = blk_mq_dequeue_from_ctx(hctx, ctx); + if (!rq) + break; + list_add(&rq->queuelist, &rq_list); + + /* round robin for fair dispatch */ + ctx = blk_mq_next_ctx(hctx, rq->mq_ctx); + + } while (blk_mq_dispatch_rq_list(q, &rq_list)); + + WRITE_ONCE(hctx->dispatch_from, ctx); +} + void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) { struct request_queue *q = hctx->queue; @@ -143,10 +176,23 @@ void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) */ if (!list_empty(&rq_list)) { blk_mq_sched_mark_restart_hctx(hctx); - if (blk_mq_dispatch_rq_list(q, &rq_list) && has_sched_dispatch) - blk_mq_do_dispatch_sched(hctx); + if (blk_mq_dispatch_rq_list(q, &rq_list)) { + if (has_sched_dispatch) + blk_mq_do_dispatch_sched(hctx); + else + blk_mq_do_dispatch_ctx(hctx); + } } else if (has_sched_dispatch) { blk_mq_do_dispatch_sched(hctx); + } else if (q->queue_depth) { + /* + * If there is per-request_queue depth, we dequeue + * request one by one from sw queue for avoiding to mess + * up I/O merge when dispatch runs out of resource, which + * can be triggered easily when there is per-request_queue + * queue depth or .cmd_per_lun, such as SCSI device. + */ + blk_mq_do_dispatch_ctx(hctx); } else { blk_mq_flush_busy_ctxs(hctx, &rq_list); blk_mq_dispatch_rq_list(q, &rq_list); diff --git a/block/blk-mq.c b/block/blk-mq.c index 076cbab9c3e0..394cb75d66fa 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -911,6 +911,45 @@ void blk_mq_flush_busy_ctxs(struct blk_mq_hw_ctx *hctx, struct list_head *list) } EXPORT_SYMBOL_GPL(blk_mq_flush_busy_ctxs); +struct dispatch_rq_data { + struct blk_mq_hw_ctx *hctx; + struct request *rq; +}; + +static bool dispatch_rq_from_ctx(struct sbitmap *sb, unsigned int bitnr, + void *data) +{ + struct dispatch_rq_data *dispatch_data = data; + struct blk_mq_hw_ctx *hctx = dispatch_data->hctx; + struct blk_mq_ctx *ctx = hctx->ctxs[bitnr]; + + spin_lock(&ctx->lock); + if (unlikely(!list_empty(&ctx->rq_list))) { + dispatch_data->rq = list_entry_rq(ctx->rq_list.next); + list_del_init(&dispatch_data->rq->queuelist); + if (list_empty(&ctx->rq_list)) + sbitmap_clear_bit(sb, bitnr); + } + spin_unlock(&ctx->lock); + + return !dispatch_data->rq; +} + +struct request *blk_mq_dequeue_from_ctx(struct blk_mq_hw_ctx *hctx, + struct blk_mq_ctx *start) +{ + unsigned off = start ? start->index_hw : 0; + struct dispatch_rq_data data = { + .hctx = hctx, + .rq = NULL, + }; + + __sbitmap_for_each_set(&hctx->ctx_map, off, + dispatch_rq_from_ctx, &data); + + return data.rq; +} + static inline unsigned int queued_to_index(unsigned int queued) { if (!queued) diff --git a/block/blk-mq.h b/block/blk-mq.h index ef15b3414da5..231cfb0d973b 100644 --- a/block/blk-mq.h +++ b/block/blk-mq.h @@ -35,6 +35,8 @@ void blk_mq_flush_busy_ctxs(struct blk_mq_hw_ctx *hctx, struct list_head *list); bool blk_mq_hctx_has_pending(struct blk_mq_hw_ctx *hctx); bool blk_mq_get_driver_tag(struct request *rq, struct blk_mq_hw_ctx **hctx, bool wait); +struct request *blk_mq_dequeue_from_ctx(struct blk_mq_hw_ctx *hctx, + struct blk_mq_ctx *start); /* * Internal helpers for allocating/freeing the request map diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index 50c6485cb04f..7b7a366a97f3 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -30,6 +30,8 @@ struct blk_mq_hw_ctx { struct sbitmap ctx_map; + struct blk_mq_ctx *dispatch_from; + struct blk_mq_ctx **ctxs; unsigned int nr_ctx;