From patchwork Mon Apr 4 09:28:04 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Suwan Kim X-Patchwork-Id: 12800044 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 72219C433F5 for ; Mon, 4 Apr 2022 09:28:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353733AbiDDJal (ORCPT ); Mon, 4 Apr 2022 05:30:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50132 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347122AbiDDJah (ORCPT ); Mon, 4 Apr 2022 05:30:37 -0400 Received: from mail-pl1-x634.google.com (mail-pl1-x634.google.com [IPv6:2607:f8b0:4864:20::634]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 50C9D1C914 for ; Mon, 4 Apr 2022 02:28:40 -0700 (PDT) Received: by mail-pl1-x634.google.com with SMTP id n9so2957224plc.4 for ; Mon, 04 Apr 2022 02:28:40 -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=9ep1sHyncwPFmrV4yxIycNkHc5iTuUAR5AyvfLy/8F4=; b=KwMJVcGqNu19VrD/oyTFcghkoa3oayoUQnLiaG4Os9WwyJfaRi0lIA9Qj+IA+qWVjN W4qY4cLIP4T8jBjT+rbmTTAP1ByccZXGUHL1l1Jjn8kEAzyLT8IZ2mkMghGQxaRHPT8U dOz9UC9OFaaLGX0g8Op3NbIfiNP93rHtt0XJRY/O9omEStI2CM7QnSnkFeztcbE/sWFt 79rBax5BK8j6qOe+x/fV/9DYGBzuF0Dds/BaDhtzySxihfxULeB9BKOEd1P+B3kMY0XH x7lP49ndrRiAcK/Ex8nxW+XVdJC5/DlBU9BqB9pLQ054ZG6pc0OCpEQHRr5Hpd5KiMUp KCvA== 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=9ep1sHyncwPFmrV4yxIycNkHc5iTuUAR5AyvfLy/8F4=; b=0DfGDtMmvHoF3Tve/Xc4AfbwQwuHGpIpGsiVt1JHe942TIgNMnvAxaObJxdoEADcLu 131OIOx3RL+2K6/VDuRtTsE4ygkUldJpj4lWU62qR9bdgysXZ8uDbqeP6AgzZCBym7VA +FtFHuoOvLqVrEEzeRs0LMejyWpdysyc6lUg/LSswiL4RlF/dyba4dGaUGa/BhqLhSyx 9YZwV6G3jHaqEw+b+uJKRDWSnPCqh2NHXQ2QIM6hsffjKAHVP5NcGCBEnUTZd5+h4YBL e6XkCAXTtpQV6m3FqNDSDrH1k3iuFfAtV07tiA329K9Qa5KLizxnjrjGd4KgKHfZncOQ ezmA== X-Gm-Message-State: AOAM530Woa0kAeZ0G0pfj/p6N9QvNXVGwPLzQppHyvNxCfEaYqveZgcW yfjgwFAvlsDww7RVr/JZ1tc= X-Google-Smtp-Source: ABdhPJyWn6Enzwz5PDIYyPX1FkUceoMXaBY8vkzmOQXnq5iRAqIhffKAUPFgFu4eS+ZMJA24eXuZzw== X-Received: by 2002:a17:90b:4d08:b0:1c7:7567:9f6b with SMTP id mw8-20020a17090b4d0800b001c775679f6bmr25761675pjb.134.1649064519769; Mon, 04 Apr 2022 02:28:39 -0700 (PDT) Received: from localhost.localdomain ([114.200.4.15]) by smtp.googlemail.com with ESMTPSA id x9-20020a17090a970900b001ca6c59b350sm6187675pjo.2.2022.04.04.02.28.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 Apr 2022 02:28:38 -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 Cc: virtualization@lists.linux-foundation.org, linux-block@vger.kernel.org, Suwan Kim Subject: [PATCH v4 1/2] virtio-blk: support polling I/O Date: Mon, 4 Apr 2022 18:28:04 +0900 Message-Id: <20220404092805.77643-2-suwan.kim027@gmail.com> X-Mailer: git-send-email 2.26.3 In-Reply-To: <20220404092805.77643-1-suwan.kim027@gmail.com> References: <20220404092805.77643-1-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 "num_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 "num_poll_queues". If VM sets queue parameter as below, ("num-queues=N" [QEMU property], "num_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 Signed-off-by: Suwan Kim --- drivers/block/virtio_blk.c | 112 +++++++++++++++++++++++++++++++++++-- 1 file changed, 108 insertions(+), 4 deletions(-) diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index 8c415be86732..c2d955da0006 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 num_poll_queues; +module_param(num_poll_queues, uint, 0644); +MODULE_PARM_DESC(num_poll_queues, "The number of dedicated virtqueues for polling I/O"); + static int major; static DEFINE_IDA(vd_index_ida); @@ -81,6 +85,7 @@ struct virtio_blk { /* num of vqs */ int num_vqs; + int io_queues[HCTX_MAX_TYPES]; struct virtio_blk_vq *vqs; }; @@ -548,6 +553,7 @@ 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, }; @@ -556,6 +562,7 @@ 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; @@ -565,6 +572,18 @@ 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, num_poll_queues, num_vqs - 1); + + memset(vblk->io_queues, 0, sizeof(int) * HCTX_MAX_TYPES); + 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; @@ -578,8 +597,13 @@ static int init_vq(struct virtio_blk *vblk) } for (i = 0; i < num_vqs; i++) { - callbacks[i] = virtblk_done; - snprintf(vblk->vqs[i].name, VQ_NAME_LEN, "req.%d", i); + if (i < num_vqs - num_poll_vqs) { + callbacks[i] = virtblk_done; + snprintf(vblk->vqs[i].name, VQ_NAME_LEN, "req.%d", i); + } else { + callbacks[i] = NULL; + snprintf(vblk->vqs[i].name, VQ_NAME_LEN, "req_poll.%d", i); + } names[i] = vblk->vqs[i].name; } @@ -728,16 +752,93 @@ 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_DEFAULT) + blk_mq_virtio_map_queues(&set->map[i], vblk->vdev, 0); + else + blk_mq_map_queues(&set->map[i]); + } + + return 0; +} + +static void virtblk_complete_batch(struct io_comp_batch *iob) +{ + struct request *req; + struct virtblk_req *vbr; + + rq_list_for_each(&iob->req_list, req) { + vbr = blk_mq_rq_to_pdu(req); + virtblk_unmap_data(req, vbr); + 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; + bool req_done = false; + 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); - return blk_mq_virtio_map_queues(&set->map[HCTX_TYPE_DEFAULT], - vblk->vdev, 0); + found++; + if (!blk_mq_add_to_batch(req, iob, vbr->status, + virtblk_complete_batch)) + blk_mq_complete_request(req); + req_done = true; + } + + if (req_done) + 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; @@ -816,6 +917,9 @@ 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)