From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 55E80D462B9 for ; Wed, 13 Nov 2024 15:21:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=RU60UgvAWZdtjyyk0hAKOkebdmlSvPmCWHzttyHTGIw=; b=asylxBlgtsN3N2699/NmlgEvux U/pp2oSW9vsFfbKWxHnFdVx1ETfxSCqxxhD77Doqh2gPwkvwuwGLsWuvIrpOhSKmbrKeLRo/tCN75 cjwTHp5Y2NjpsQ1HVK7li4rKMBtVAHE0fO/YcEo86bJrMF2vJGQLsgEX4vFnfDOcKzGAQcO1uPva3 c2NlegcLHuS/Q1PrHTfrlANAmZVZ1hnofeA4xIIa8PHG0a9I56RGTYw2AtjD5m/tle7wf41vT+UNN HLSVWT3xziDFkOJt9rDXw0B9+HVh8A/TNgK4X+qML3vYjm0x7IMVlZvVRpNc7IvBoDnLAy/du8LIH qPXHKmvw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tBFAz-00000007HMW-338H; Wed, 13 Nov 2024 15:21:01 +0000 Received: from 2a02-8389-2341-5b80-9e61-c6cf-2f07-a796.cable.dynamic.v6.surfer.at ([2a02:8389:2341:5b80:9e61:c6cf:2f07:a796] helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tBFAx-00000007HKx-3UbT; Wed, 13 Nov 2024 15:21:00 +0000 From: Christoph Hellwig To: Jens Axboe Cc: "Michael S. Tsirkin" , Jason Wang , Keith Busch , Sagi Grimberg , Pavel Begunkov , linux-block@vger.kernel.org, virtualization@lists.linux.dev, linux-nvme@lists.infradead.org, io-uring@vger.kernel.org Subject: [PATCH 2/6] virtio_blk: reverse request order in virtio_queue_rqs Date: Wed, 13 Nov 2024 16:20:42 +0100 Message-ID: <20241113152050.157179-3-hch@lst.de> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20241113152050.157179-1-hch@lst.de> References: <20241113152050.157179-1-hch@lst.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org blk_mq_flush_plug_list submits requests in the reverse order that they were submitted, which leads to a rather suboptimal I/O pattern especially in rotational devices. Fix this by rewriting nvme_queue_rqs so that it always pops the requests from the passed in request list, and then adds them to the head of a local submit list. This actually simplifies the code a bit as it removes the complicated list splicing, at the cost of extra updates of the rq_next pointer. As that should be cache hot anyway it should be an easy price to pay. Fixes: 0e9911fa768f ("virtio-blk: support mq_ops->queue_rqs()") Signed-off-by: Christoph Hellwig --- drivers/block/virtio_blk.c | 46 +++++++++++++++++--------------------- 1 file changed, 21 insertions(+), 25 deletions(-) diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index 0e99a4714928..b25f7c06a28e 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -471,18 +471,18 @@ static bool virtblk_prep_rq_batch(struct request *req) return virtblk_prep_rq(req->mq_hctx, vblk, req, vbr) == BLK_STS_OK; } -static bool virtblk_add_req_batch(struct virtio_blk_vq *vq, +static void virtblk_add_req_batch(struct virtio_blk_vq *vq, struct request **rqlist) { + struct request *req; unsigned long flags; - int err; bool kick; spin_lock_irqsave(&vq->lock, flags); - while (!rq_list_empty(*rqlist)) { - struct request *req = rq_list_pop(rqlist); + while ((req = rq_list_pop(rqlist))) { struct virtblk_req *vbr = blk_mq_rq_to_pdu(req); + int err; err = virtblk_add_req(vq->vq, vbr); if (err) { @@ -495,37 +495,33 @@ static bool virtblk_add_req_batch(struct virtio_blk_vq *vq, kick = virtqueue_kick_prepare(vq->vq); spin_unlock_irqrestore(&vq->lock, flags); - return kick; + if (kick) + virtqueue_notify(vq->vq); } static void virtio_queue_rqs(struct request **rqlist) { - struct request *req, *next, *prev = NULL; + struct request *submit_list = NULL; struct request *requeue_list = NULL; + struct request **requeue_lastp = &requeue_list; + struct virtio_blk_vq *vq = NULL; + struct request *req; - rq_list_for_each_safe(rqlist, req, next) { - struct virtio_blk_vq *vq = get_virtio_blk_vq(req->mq_hctx); - bool kick; - - if (!virtblk_prep_rq_batch(req)) { - rq_list_move(rqlist, &requeue_list, req, prev); - req = prev; - if (!req) - continue; - } + while ((req = rq_list_pop(rqlist))) { + struct virtio_blk_vq *this_vq = get_virtio_blk_vq(req->mq_hctx); - if (!next || req->mq_hctx != next->mq_hctx) { - req->rq_next = NULL; - kick = virtblk_add_req_batch(vq, rqlist); - if (kick) - virtqueue_notify(vq->vq); + if (vq && vq != this_vq) + virtblk_add_req_batch(vq, &submit_list); + vq = this_vq; - *rqlist = next; - prev = NULL; - } else - prev = req; + if (virtblk_prep_rq_batch(req)) + rq_list_add(&submit_list, req); /* reverse order */ + else + rq_list_add_tail(&requeue_lastp, req); } + if (vq) + virtblk_add_req_batch(vq, &submit_list); *rqlist = requeue_list; } -- 2.45.2