From patchwork Mon May 25 09:38:07 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ming Lei X-Patchwork-Id: 11568481 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id D17221391 for ; Mon, 25 May 2020 09:39:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B92E22073B for ; Mon, 25 May 2020 09:39:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="BHTWtDEe" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389520AbgEYJjK (ORCPT ); Mon, 25 May 2020 05:39:10 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:59065 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2389367AbgEYJjK (ORCPT ); Mon, 25 May 2020 05:39:10 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1590399548; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=OjNiUE7gDtN0yF/gxU1VFRPBtu2E3U8ObEBp3r1kD3o=; b=BHTWtDEeDVxo+upssoKONDsvpoNqoGDGGNMrw1DN6bpkHm+97NQv1T4fkHZ+gfeDjQM8N7 DytYBLIMFd/TJZQCXI294QI4ZAf2UzK/QBvgeZXElAdsXkIpg9YLKvuoPsnSNQ0UGF9K1A djrz2j+3z6Mei4I6rRZ2Zxx3P/2QRfU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-93-G107ELwMPQi_qH4ZdaQDig-1; Mon, 25 May 2020 05:39:05 -0400 X-MC-Unique: G107ELwMPQi_qH4ZdaQDig-1 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 mimecast-mx01.redhat.com (Postfix) with ESMTPS id BD8C380B700; Mon, 25 May 2020 09:39:03 +0000 (UTC) Received: from localhost (ovpn-12-137.pek2.redhat.com [10.72.12.137]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7ABDA1CA; Mon, 25 May 2020 09:38:59 +0000 (UTC) From: Ming Lei To: Jens Axboe Cc: linux-block@vger.kernel.org, Ming Lei , Sagi Grimberg , Baolin Wang , Christoph Hellwig Subject: [PATCH V2 6/6] blk-mq: support batching dispatch in case of io scheduler Date: Mon, 25 May 2020 17:38:07 +0800 Message-Id: <20200525093807.805155-7-ming.lei@redhat.com> In-Reply-To: <20200525093807.805155-1-ming.lei@redhat.com> References: <20200525093807.805155-1-ming.lei@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org More and more drivers want to get batching requests queued from block layer, such as mmc, and tcp based storage drivers. Also current in-tree users have virtio-scsi, virtio-blk and nvme. For none, we already support batching dispatch. But for io scheduler, every time we just take one request from scheduler and pass the single request to blk_mq_dispatch_rq_list(). This way makes batching dispatch not possible when io scheduler is applied. One reason is that we don't want to hurt sequential IO performance, becasue IO merge chance is reduced if more requests are dequeued from scheduler queue. Try to support batching dispatch for io scheduler by starting with the following simple approach: 1) still make sure we can get budget before dequeueing request 2) use hctx->dispatch_busy to evaluate if queue is busy, if it is busy we fackback to non-batching dispatch, otherwise dequeue as many as possible requests from scheduler, and pass them to blk_mq_dispatch_rq_list(). Wrt. 2), we use similar policy for none, and turns out that SCSI SSD performance got improved much. In future, maybe we can develop more intelligent algorithem for batching dispatch. [1] https://lore.kernel.org/linux-block/20200512075501.GF1531898@T590/#r [2] https://lore.kernel.org/linux-block/fe6bd8b9-6ed9-b225-f80c-314746133722@grimberg.me/ Cc: Sagi Grimberg Cc: Baolin Wang Cc: Christoph Hellwig Signed-off-by: Ming Lei --- block/blk-mq-sched.c | 75 +++++++++++++++++++++++++++++++++++++++++++- block/blk-mq.c | 2 -- 2 files changed, 74 insertions(+), 3 deletions(-) diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c index 4c72073830f3..75cf9528ac01 100644 --- a/block/blk-mq-sched.c +++ b/block/blk-mq-sched.c @@ -7,6 +7,7 @@ #include #include #include +#include #include @@ -80,6 +81,68 @@ void blk_mq_sched_restart(struct blk_mq_hw_ctx *hctx) blk_mq_run_hw_queue(hctx, true); } +/* + * We know bfq and deadline apply single scheduler queue instead of multi + * queue. However, the two are often used on single queue devices, also + * the current @hctx should affect the real device status most of times + * because of locality principle. + * + * So use current hctx->dispatch_busy directly for figuring out batching + * dispatch count. + */ +static unsigned int blk_mq_sched_get_batching_nr(struct blk_mq_hw_ctx *hctx) +{ + if (hctx->dispatch_busy) + return 1; + return hctx->queue->nr_requests; +} + +static int sched_rq_cmp(void *priv, struct list_head *a, struct list_head *b) +{ + struct request *rqa = container_of(a, struct request, queuelist); + struct request *rqb = container_of(b, struct request, queuelist); + + return rqa->mq_hctx > rqb->mq_hctx; +} + +static inline void blk_mq_do_dispatch_rq_lists(struct blk_mq_hw_ctx *hctx, + struct list_head *lists, bool multi_hctxs, unsigned count) +{ + if (likely(!multi_hctxs)) { + blk_mq_dispatch_rq_list(hctx, lists, count); + return; + } + + /* + * Requests from different hctx may be dequeued from some scheduler, + * such as bfq and deadline. + * + * Sort the requests in the list according to their hctx, dispatch + * batching requests from same hctx + */ + list_sort(NULL, lists, sched_rq_cmp); + + while (!list_empty(lists)) { + LIST_HEAD(list); + struct request *new, *rq = list_first_entry(lists, + struct request, queuelist); + unsigned cnt = 0; + + list_for_each_entry(new, lists, queuelist) { + if (new->mq_hctx != rq->mq_hctx) + break; + cnt++; + } + + if (new->mq_hctx == rq->mq_hctx) + list_splice_tail_init(lists, &list); + else + list_cut_before(&list, lists, &new->queuelist); + + blk_mq_dispatch_rq_list(rq->mq_hctx, &list, cnt); + } +} + #define BLK_MQ_BUDGET_DELAY 3 /* ms units */ /* @@ -97,6 +160,9 @@ static int blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx) LIST_HEAD(rq_list); int ret = 0; struct request *rq; + int cnt = 0; + unsigned int max_dispatch = blk_mq_sched_get_batching_nr(hctx); + bool multi_hctxs = false; do { if (e->type->ops.has_work && !e->type->ops.has_work(hctx)) @@ -130,7 +196,14 @@ static int blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx) * in blk_mq_dispatch_rq_list(). */ list_add(&rq->queuelist, &rq_list); - } while (blk_mq_dispatch_rq_list(rq->mq_hctx, &rq_list, 1)); + cnt++; + + if (rq->mq_hctx != hctx && !multi_hctxs) + multi_hctxs = true; + } while (cnt < max_dispatch); + + if (cnt) + blk_mq_do_dispatch_rq_lists(hctx, &rq_list, multi_hctxs, cnt); return ret; } diff --git a/block/blk-mq.c b/block/blk-mq.c index 3f672b2662a9..ed61811e1611 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1281,8 +1281,6 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list, if (list_empty(list)) return false; - WARN_ON(!list_is_singular(list) && nr_budgets); - /* * Now process all the entries, sending them to the driver. */