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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 83B95C433F5 for ; Sat, 26 Mar 2022 12:44:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232917AbiCZMqP (ORCPT ); Sat, 26 Mar 2022 08:46:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41954 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232936AbiCZMqO (ORCPT ); Sat, 26 Mar 2022 08:46:14 -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 D7321137013 for ; Sat, 26 Mar 2022 05:44:37 -0700 (PDT) Received: by mail-pl1-x634.google.com with SMTP id c23so10840517plo.0 for ; Sat, 26 Mar 2022 05:44:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=vPtd+23ig1Bvitv472qzWpC8hGPkMq7EaGySCH/wNjA=; b=PYN73m9lVQnviWoRaYSYEWOBI4PAgL9qi5AUQi+cww1g1T+DQ5zaYjtVhSFXFXgrWq H3sHdAy/uFM8QTMUyLbZPjn5WYbpTA7DbbviBfdA1zHwcbbWNZMViLNTXGMYLWzIHqdu UYIqk8sVUv8l4UdlWHu3Vewy7R3kLSuZFNq5QW8TzkeOewzgdW3ld57kaK3pdDrNxLh3 6EMYUkYAoYDWOFskxyDIBP5o6JmWYjCEVFBzYXMkMvjl8RTtqgRFzmnE+9FbB2k6sScq Mx6InUV4mMGBycC8/Sfxds1JNWjXMFT9mwi4so6MTDYzQnL0jXmGk0rhL1RthD0jTUbN b4zg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=vPtd+23ig1Bvitv472qzWpC8hGPkMq7EaGySCH/wNjA=; b=v6DodPtm2W0dEKVAKOCbFq8xp8HktZigArQElquT1B2BMv0jH8kHfvHH7LFzxSRpOJ L5mGkRxrl+fgLKOePygLDJ74Rz0DsXbGWfzvPHcPbwLl3d+0khLxq/QtdxEIukosR5P3 I+1Jg8qxnmiamhOMnJgtrsG3k/FKMtBJhtDhnk/dPwf8SBMyaxtghjVMxaZEgAfT6yAX js8lhOYEMkeahCehnz6itmPicvPAkiuX2t0WfiudQfzaCmn6onl504iPySH2iUp0TLxD AZaMfnqdssbq5+WpqSAEiwKqi7nE2qRZv3kmjmeRdkJ++Msend2WS5UEVfY7c1eq+dgi D/WQ== X-Gm-Message-State: AOAM533zLLZkV7tzkhin41WWupgtl0ZuhDW38i/irLiTRxePfMGrxvga 47cpzP3xfUrr7SGy8UjAVz4= X-Google-Smtp-Source: ABdhPJz/RVTzF9EE71/Yp5djfJyexBZ36E1roXxHPY1KnVTOYARaxiXl+sNhQHJFVBdfIxP04XOH/w== X-Received: by 2002:a17:90a:db08:b0:1c9:7cf3:6363 with SMTP id g8-20020a17090adb0800b001c97cf36363mr1665506pjv.35.1648298677262; Sat, 26 Mar 2022 05:44:37 -0700 (PDT) Received: from localhost.localdomain ([114.200.4.15]) by smtp.gmail.com with ESMTPSA id nv11-20020a17090b1b4b00b001c71b0bf18bsm16130073pjb.11.2022.03.26.05.44.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 26 Mar 2022 05:44:36 -0700 (PDT) Date: Sat, 26 Mar 2022 21:44:30 +0900 From: Suwan Kim To: "Michael S. Tsirkin" Cc: jasowang@redhat.com, stefanha@redhat.com, pbonzini@redhat.com, mgurtovoy@nvidia.com, virtualization@lists.linux-foundation.org, linux-block@vger.kernel.org, kernel test robot Subject: Re: [PATCH v3 1/2] virtio-blk: support polling I/O Message-ID: References: <20220324140450.33148-1-suwan.kim027@gmail.com> <20220324140450.33148-2-suwan.kim027@gmail.com> <20220324135647-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220324135647-mutt-send-email-mst@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Thu, Mar 24, 2022 at 01:58:28PM -0400, Michael S. Tsirkin wrote: > On Thu, Mar 24, 2022 at 11:04:49PM +0900, Suwan Kim wrote: > > 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 = 380K, avg latency = 167.87us > > -- numjobs=2 : IOPS = 409K, avg latency = 312.6us > > -- numjobs=4 : IOPS = 413K, avg latency = 619.72us > > > > Reported-by: kernel test robot > > Signed-off-by: Suwan Kim > > --- > > drivers/block/virtio_blk.c | 101 +++++++++++++++++++++++++++++++++++-- > > 1 file changed, 97 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c > > index 8c415be86732..3d16f8b753e7 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 +572,13 @@ 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_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; > > + > > vblk->vqs = kmalloc_array(num_vqs, sizeof(*vblk->vqs), GFP_KERNEL); > > if (!vblk->vqs) > > return -ENOMEM; > > @@ -578,8 +592,13 @@ 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 +747,87 @@ 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; > > > > - 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, vbr->status, > > + 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 +906,9 @@ 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) > > > > So wrt cleanup, does something poll for all buffers to be > used when device is removed? Sorry for late reply. Maybe below function calls iterate each HW queue and flush requests before device is removed? ----- virtblk_remove() -> blk_cleanup_disk()/blk_cleanup_queue() -> blk_queue_start_drain()/blk_freeze_queue() ----- Regards, Suwan Kim