From patchwork Fri Mar 11 15:28:32 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Suwan Kim X-Patchwork-Id: 12778249 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 89EB0C433EF for ; Fri, 11 Mar 2022 15:29:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230378AbiCKPaO (ORCPT ); Fri, 11 Mar 2022 10:30:14 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45316 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346160AbiCKPaN (ORCPT ); Fri, 11 Mar 2022 10:30:13 -0500 Received: from mail-pj1-x102f.google.com (mail-pj1-x102f.google.com [IPv6:2607:f8b0:4864:20::102f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 27B801BBF75 for ; Fri, 11 Mar 2022 07:29:10 -0800 (PST) Received: by mail-pj1-x102f.google.com with SMTP id 15-20020a17090a098f00b001bef0376d5cso8408906pjo.5 for ; Fri, 11 Mar 2022 07:29:10 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=57NOhTMpNENEvLVemQUZurVSM2I6aHGnxhej2brNtRI=; b=FAu6uKQE5G6MmcSSROEoqt+9QPjmxkh5GdR/bvhwqqev4iRtuKC5k2icz4MeOYtIaz p1v8b5PbvZAxbngmATbE2I8ijpEli956Al6WlTNBcggY8OYvzYLAdUbP2PL6KaP/+TzC 5Y0Cwz2eIqlwOTZzX+ZH4PRB1wSBPn7eutFFVrvL4CcvhGRlDsUoqzRJLiOOL6HBnEU2 qlm6l2Q4E59RD7qe5PaGVPxJXRLbYgI+joDrDINUO6IXxlzWZ9EtDfJkfa0IwdAxsSLw YIDx7iLsgSTxY3GUlmGVgpgASl12Xv2Ca0wTUZaB96NrZPxnWiYxFasUj8Np8Ah9cpYL l3mw== 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:mime-version :content-transfer-encoding; bh=57NOhTMpNENEvLVemQUZurVSM2I6aHGnxhej2brNtRI=; b=ovfcmGkZpGjcPY8NO/0v1AlUxi70JlSC8sFP4uCy2rQoT7dYHKfyEJWavqYr3zlstE HFMtePQvJHQwBc413VXOmUloDLuEQZuu4UQcWQ+LzxfQGCvTPOKUu37f7lrm/eGM4Zul eaVNkv0xzr7UlmxqNm2hAfJCi3am/EDd741zl/rVsJ1VzrWCtQ+g0Eagy7QFGFxmMJ1R PuhMHjfj00zoXsAFz8wDiaFDMTEIBuC9YDIDkTAoPIW51B1Wspi874Gvb5d/4I/7zOrM HH7DpXg3lPU+yaHgPCtO8wDHswLnz2TFamLpTy4NQYUMxOB4Tmhp+FKb/5mrze0Fs1+h bpTQ== X-Gm-Message-State: AOAM530/Hbfk/ORhExCl74pW7W73TPeG/tJ9vO3PS30O3oWeYxdgYCtq ZMFk8XrJaIK1N12Z3G8nWeQ= X-Google-Smtp-Source: ABdhPJw+V2CBB6NMo8X9qxQ+LTTdjSfoatrRQSEjftd4bFl/ggxKDwhEELu+fZ0m6QIwSPYCiahpkQ== X-Received: by 2002:a17:902:e54c:b0:151:e2f3:9ee7 with SMTP id n12-20020a170902e54c00b00151e2f39ee7mr10969297plf.61.1647012549602; Fri, 11 Mar 2022 07:29:09 -0800 (PST) Received: from localhost.localdomain ([114.200.4.15]) by smtp.googlemail.com with ESMTPSA id lb4-20020a17090b4a4400b001b9b20eabc4sm10457663pjb.5.2022.03.11.07.29.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 11 Mar 2022 07:29:08 -0800 (PST) From: Suwan Kim To: mst@redhat.com, jasowang@redhat.com, pbonzini@redhat.com, stefanha@redhat.com Cc: virtualization@lists.linux-foundation.org, linux-block@vger.kernel.org, Suwan Kim Subject: [PATCH] virtio-blk: support polling I/O Date: Sat, 12 Mar 2022 00:28:32 +0900 Message-Id: <20220311152832.17703-1-suwan.kim027@gmail.com> X-Mailer: git-send-email 2.26.3 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 based on "VIRTIO_BLK_F_MQ" feature and the number of polling queues can be set by QEMU virtio-blk-pci property "num-poll-queues=N". 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 queues and poll queues from QEMU virtio-blk-pci properties ("num-queues=N", "num-poll-queues=M"). 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. To enable poll queues, "num-poll-queues=N" property of virtio-blk-pci needs to be added to QEMU command line. For that, I temporarily implemented the property on QEMU. Please refer to the git repository below. git : https://github.com/asfaca/qemu.git #on master branch commit 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. (-device virtio-blk-pci,num-queues=4,num-poll-queues=2) As a result, IOPS and average latency improved about 10%. Test result: - Fio io_uring poll without virtio-blk poll support -- numjobs=1 : IOPS = 297K, avg latency = 214.59us -- numjobs=2 : IOPS = 360K, avg latency = 363.88us -- numjobs=4 : IOPS = 289K, avg latency = 885.42us - Fio io_uring poll with virtio-blk poll support -- numjobs=1 : IOPS = 332K, avg latency = 192.61us -- numjobs=2 : IOPS = 371K, avg latency = 348.31us -- numjobs=4 : IOPS = 321K, avg latency = 795.93us Signed-off-by: Suwan Kim --- drivers/block/virtio_blk.c | 98 +++++++++++++++++++++++++++++++-- include/uapi/linux/virtio_blk.h | 3 +- 2 files changed, 96 insertions(+), 5 deletions(-) diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index 8c415be86732..bfde7d97d528 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -81,6 +81,7 @@ struct virtio_blk { /* num of vqs */ int num_vqs; + int io_queues[HCTX_MAX_TYPES]; struct virtio_blk_vq *vqs; }; @@ -548,6 +549,7 @@ static int init_vq(struct virtio_blk *vblk) const char **names; struct virtqueue **vqs; unsigned short num_vqs; + unsigned short num_poll_vqs; struct virtio_device *vdev = vblk->vdev; struct irq_affinity desc = { 0, }; @@ -556,6 +558,13 @@ static int init_vq(struct virtio_blk *vblk) &num_vqs); if (err) num_vqs = 1; + + err = virtio_cread_feature(vdev, VIRTIO_BLK_F_MQ, + struct virtio_blk_config, num_poll_queues, + &num_poll_vqs); + if (err) + num_poll_vqs = 0; + if (!err && !num_vqs) { dev_err(&vdev->dev, "MQ advertised but zero queues reported\n"); return -EINVAL; @@ -565,6 +574,13 @@ 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_vqs, 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; + vblk->vqs = kmalloc_array(num_vqs, sizeof(*vblk->vqs), GFP_KERNEL); if (!vblk->vqs) return -ENOMEM; @@ -578,8 +594,13 @@ 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 +749,82 @@ 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; + + 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; - return blk_mq_virtio_map_queues(&set->map[HCTX_TYPE_DEFAULT], - vblk->vdev, 0); + 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_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, virtblk_result(vbr), + virtblk_complete_batch)) + blk_mq_complete_request(req); + } + + 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 +903,9 @@ 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) diff --git a/include/uapi/linux/virtio_blk.h b/include/uapi/linux/virtio_blk.h index d888f013d9ff..3fcaf937afe1 100644 --- a/include/uapi/linux/virtio_blk.h +++ b/include/uapi/linux/virtio_blk.h @@ -119,8 +119,9 @@ struct virtio_blk_config { * deallocation of one or more of the sectors. */ __u8 write_zeroes_may_unmap; + __u8 unused1; - __u8 unused1[3]; + __virtio16 num_poll_queues; } __attribute__((packed)); /*