From patchwork Wed Apr 6 15:32:06 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Suwan Kim X-Patchwork-Id: 12803879 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 57035C433F5 for ; Wed, 6 Apr 2022 17:28:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239243AbiDFRaN (ORCPT ); Wed, 6 Apr 2022 13:30:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37476 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239177AbiDFR37 (ORCPT ); Wed, 6 Apr 2022 13:29:59 -0400 Received: from mail-pf1-x430.google.com (mail-pf1-x430.google.com [IPv6:2607:f8b0:4864:20::430]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EDCBB6377 for ; Wed, 6 Apr 2022 08:32:59 -0700 (PDT) Received: by mail-pf1-x430.google.com with SMTP id s8so2746564pfk.12 for ; Wed, 06 Apr 2022 08:32:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=QUWEtqdcs6FvknA2cur3eZm3P9mBxM8axKf5gzGdnMg=; b=LUeQ9OYBL0Z2v3DhtaxJaz4oaaf4bdyZcBECl0nfDraADBw3KtJeGPRDCl0OwzOkN3 G2Y9rBB1eyQ2GKCjpS0U6ew5Wzq4xOtmxjXdBmp8YNzdPFS5YGVcnlUjS6ompLkzvmV0 gQhSupzZyB4zfu8StdkBFCM4rSk8p/yLmPL9tm6m2ganYTFHDL7rZ4PFBDsVbIvzxK1A lX6ksQqICCzb5FJYHvgxufQPthuheCiU7anydOiMYpSpuaeHojDhy8splNLSNgY0JDhr hmbXJdmOR22C+aBrUhA/dIyDcVzUtJZssMWqFaNXHLXKi22yfAs+XZpuDmTpRuKRolum YjOg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=QUWEtqdcs6FvknA2cur3eZm3P9mBxM8axKf5gzGdnMg=; b=djGzzyeuvb2E396d633rdOQk+jviRzhTTQJc/y1aajR4x89UApPT3yosWIVrHSX3Ld gNdTHjRuSd83qlCzlerIfU2AWdBmFhde8EuCGfu8rxR91KlbnZzRmC2gQphAkcGQ7Qh5 a7ddZJag8E6eV0Tum77NhkogedWOpIczxLO7if6DhZXj09hdsOCHzDKvyvD2XrDtXveW E5UYAz+J/me0wpclTcbVgQqMVFr2ctVuoB1EfG4ZorA98mH3XvX1/L+Lj8QLY2gNRTMv ETZCpdUVx//tSkFoJrX8VpVBlJTIZF6fOG/LqVas05auer4PutD7Y6PVJrXbH33wk9iB 0ZAQ== X-Gm-Message-State: AOAM533mQ/2/Hetp4GxFWQcsH0ZmHXL8Vgf8VHZPlKG9beu/ElhNAKUO 10aFLGQkGcK+pmYkyZRgBEg= X-Google-Smtp-Source: ABdhPJywoNHApXu0f+gXiyPKYqHCxiJrSe2lvaLbTGseuTPrQ/J7vZlwUP3sFtQ5VZt1OOnfZZu7vQ== X-Received: by 2002:a05:6a00:22d2:b0:4fa:9d26:bc5d with SMTP id f18-20020a056a0022d200b004fa9d26bc5dmr9464501pfj.79.1649259179418; Wed, 06 Apr 2022 08:32:59 -0700 (PDT) Received: from localhost.localdomain ([114.200.4.15]) by smtp.googlemail.com with ESMTPSA id f31-20020a17090a702200b001ca996866b5sm6024037pjk.12.2022.04.06.08.32.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 06 Apr 2022 08:32:58 -0700 (PDT) From: Suwan Kim To: mst@redhat.com, jasowang@redhat.com, stefanha@redhat.com, pbonzini@redhat.com, mgurtovoy@nvidia.com, dongli.zhang@oracle.com, hch@infradead.org, elliott@hpe.com Cc: virtualization@lists.linux-foundation.org, linux-block@vger.kernel.org, Suwan Kim , Christoph Hellwig Subject: [PATCH v6 1/2] virtio-blk: support polling I/O Date: Thu, 7 Apr 2022 00:32:06 +0900 Message-Id: <20220406153207.163134-2-suwan.kim027@gmail.com> X-Mailer: git-send-email 2.26.3 In-Reply-To: <20220406153207.163134-1-suwan.kim027@gmail.com> References: <20220406153207.163134-1-suwan.kim027@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org This patch supports polling I/O via virtio-blk driver. Polling feature is enabled by module parameter "poll_queues" and it sets dedicated polling queues for virtio-blk. This patch improves the polling I/O throughput and latency. The virtio-blk driver doesn't not have a poll function and a poll queue and it has been operating in interrupt driven method even if the polling function is called in the upper layer. virtio-blk polling is implemented upon 'batched completion' of block layer. virtblk_poll() queues completed request to io_comp_batch->req_list and later, virtblk_complete_batch() calls unmap function and ends the requests in batch. virtio-blk reads the number of poll queues from module parameter "poll_queues". If VM sets queue parameter as below, ("num-queues=N" [QEMU property], "poll_queues=M" [module parameter]) It allocates N virtqueues to virtio_blk->vqs[N] and it uses [0..(N-M-1)] as default queues and [(N-M)..(N-1)] as poll queues. Unlike the default queues, the poll queues have no callback function. Regarding HW-SW queue mapping, the default queue mapping uses the existing method that condsiders MSI irq vector. But the poll queue doesn't have an irq, so it uses the regular blk-mq cpu mapping. For verifying the improvement, I did Fio polling I/O performance test with io_uring engine with the options below. (io_uring, hipri, randread, direct=1, bs=512, iodepth=64 numjobs=N) I set 4 vcpu and 4 virtio-blk queues - 2 default queues and 2 poll queues for VM. As a result, IOPS and average latency improved about 10%. Test result: - Fio io_uring poll without virtio-blk poll support -- numjobs=1 : IOPS = 339K, avg latency = 188.33us -- numjobs=2 : IOPS = 367K, avg latency = 347.33us -- numjobs=4 : IOPS = 383K, avg latency = 682.06us - Fio io_uring poll with virtio-blk poll support -- numjobs=1 : IOPS = 385K, avg latency = 165.94us -- numjobs=2 : IOPS = 408K, avg latency = 313.28us -- numjobs=4 : IOPS = 424K, avg latency = 613.05us Reviewed-by: Stefan Hajnoczi Reviewed-by: Christoph Hellwig Reviewed-by: Max Gurtovoy Signed-off-by: Suwan Kim Reviewed-by: Chaitanya Kulkarni --- drivers/block/virtio_blk.c | 106 +++++++++++++++++++++++++++++++++++-- 1 file changed, 103 insertions(+), 3 deletions(-) diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index a8bcf3f664af..957e15b87651 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -37,6 +37,10 @@ MODULE_PARM_DESC(num_request_queues, "0 for no limit. " "Values > nr_cpu_ids truncated to nr_cpu_ids."); +static unsigned int poll_queues; +module_param(poll_queues, uint, 0644); +MODULE_PARM_DESC(poll_queues, "The number of dedicated virtqueues for polling I/O"); + static int major; static DEFINE_IDA(vd_index_ida); @@ -74,6 +78,7 @@ struct virtio_blk { /* num of vqs */ int num_vqs; + int io_queues[HCTX_MAX_TYPES]; struct virtio_blk_vq *vqs; }; @@ -512,6 +517,7 @@ static int init_vq(struct virtio_blk *vblk) const char **names; struct virtqueue **vqs; unsigned short num_vqs; + unsigned int num_poll_vqs; struct virtio_device *vdev = vblk->vdev; struct irq_affinity desc = { 0, }; @@ -520,6 +526,7 @@ static int init_vq(struct virtio_blk *vblk) &num_vqs); if (err) num_vqs = 1; + if (!err && !num_vqs) { dev_err(&vdev->dev, "MQ advertised but zero queues reported\n"); return -EINVAL; @@ -529,6 +536,17 @@ static int init_vq(struct virtio_blk *vblk) min_not_zero(num_request_queues, nr_cpu_ids), num_vqs); + num_poll_vqs = min_t(unsigned int, poll_queues, num_vqs - 1); + + vblk->io_queues[HCTX_TYPE_DEFAULT] = num_vqs - num_poll_vqs; + vblk->io_queues[HCTX_TYPE_READ] = 0; + vblk->io_queues[HCTX_TYPE_POLL] = num_poll_vqs; + + dev_info(&vdev->dev, "%d/%d/%d default/read/poll queues\n", + vblk->io_queues[HCTX_TYPE_DEFAULT], + vblk->io_queues[HCTX_TYPE_READ], + vblk->io_queues[HCTX_TYPE_POLL]); + vblk->vqs = kmalloc_array(num_vqs, sizeof(*vblk->vqs), GFP_KERNEL); if (!vblk->vqs) return -ENOMEM; @@ -541,12 +559,18 @@ static int init_vq(struct virtio_blk *vblk) goto out; } - for (i = 0; i < num_vqs; i++) { + for (i = 0; i < num_vqs - num_poll_vqs; i++) { callbacks[i] = virtblk_done; snprintf(vblk->vqs[i].name, VQ_NAME_LEN, "req.%d", i); names[i] = vblk->vqs[i].name; } + for (; i < num_vqs; i++) { + callbacks[i] = NULL; + snprintf(vblk->vqs[i].name, VQ_NAME_LEN, "req_poll.%d", i); + names[i] = vblk->vqs[i].name; + } + /* Discover virtqueues and write information to configuration. */ err = virtio_find_vqs(vdev, num_vqs, vqs, callbacks, names, &desc); if (err) @@ -692,16 +716,89 @@ static const struct attribute_group *virtblk_attr_groups[] = { static int virtblk_map_queues(struct blk_mq_tag_set *set) { struct virtio_blk *vblk = set->driver_data; + int i, qoff; + + for (i = 0, qoff = 0; i < set->nr_maps; i++) { + struct blk_mq_queue_map *map = &set->map[i]; + + map->nr_queues = vblk->io_queues[i]; + map->queue_offset = qoff; + qoff += map->nr_queues; + + if (map->nr_queues == 0) + continue; + + /* + * Regular queues have interrupts and hence CPU affinity is + * defined by the core virtio code, but polling queues have + * no interrupts so we let the block layer assign CPU affinity. + */ + if (i == HCTX_TYPE_POLL) + blk_mq_map_queues(&set->map[i]); + else + blk_mq_virtio_map_queues(&set->map[i], vblk->vdev, 0); + } + + return 0; +} + +static void virtblk_complete_batch(struct io_comp_batch *iob) +{ + struct request *req; - return blk_mq_virtio_map_queues(&set->map[HCTX_TYPE_DEFAULT], - vblk->vdev, 0); + rq_list_for_each(&iob->req_list, req) { + virtblk_unmap_data(req, blk_mq_rq_to_pdu(req)); + virtblk_cleanup_cmd(req); + } + blk_mq_end_request_batch(iob); +} + +static int virtblk_poll(struct blk_mq_hw_ctx *hctx, struct io_comp_batch *iob) +{ + struct virtio_blk *vblk = hctx->queue->queuedata; + struct virtio_blk_vq *vq = hctx->driver_data; + struct virtblk_req *vbr; + unsigned long flags; + unsigned int len; + int found = 0; + + spin_lock_irqsave(&vq->lock, flags); + + while ((vbr = virtqueue_get_buf(vq->vq, &len)) != NULL) { + struct request *req = blk_mq_rq_from_pdu(vbr); + + found++; + if (!blk_mq_add_to_batch(req, iob, vbr->status, + virtblk_complete_batch)) + blk_mq_complete_request(req); + } + + if (found) + blk_mq_start_stopped_hw_queues(vblk->disk->queue, true); + + spin_unlock_irqrestore(&vq->lock, flags); + + return found; +} + +static int virtblk_init_hctx(struct blk_mq_hw_ctx *hctx, void *data, + unsigned int hctx_idx) +{ + struct virtio_blk *vblk = data; + struct virtio_blk_vq *vq = &vblk->vqs[hctx_idx]; + + WARN_ON(vblk->tag_set.tags[hctx_idx] != hctx->tags); + hctx->driver_data = vq; + return 0; } static const struct blk_mq_ops virtio_mq_ops = { .queue_rq = virtio_queue_rq, .commit_rqs = virtio_commit_rqs, + .init_hctx = virtblk_init_hctx, .complete = virtblk_request_done, .map_queues = virtblk_map_queues, + .poll = virtblk_poll, }; static unsigned int virtblk_queue_depth; @@ -778,6 +875,9 @@ static int virtblk_probe(struct virtio_device *vdev) sizeof(struct scatterlist) * VIRTIO_BLK_INLINE_SG_CNT; vblk->tag_set.driver_data = vblk; vblk->tag_set.nr_hw_queues = vblk->num_vqs; + vblk->tag_set.nr_maps = 1; + if (vblk->io_queues[HCTX_TYPE_POLL]) + vblk->tag_set.nr_maps = 3; err = blk_mq_alloc_tag_set(&vblk->tag_set); if (err)