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 7F4EAC433EF for ; Sat, 26 Mar 2022 12:01:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232046AbiCZMCf (ORCPT ); Sat, 26 Mar 2022 08:02:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48992 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232032AbiCZMCf (ORCPT ); Sat, 26 Mar 2022 08:02:35 -0400 Received: from mail-pg1-x52d.google.com (mail-pg1-x52d.google.com [IPv6:2607:f8b0:4864:20::52d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9025326AFF for ; Sat, 26 Mar 2022 05:00:58 -0700 (PDT) Received: by mail-pg1-x52d.google.com with SMTP id l129so16232pga.3 for ; Sat, 26 Mar 2022 05:00:58 -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=zhpzHaewQiFA7zyinksagIouSrpHytz8zX+SwMrxXA0=; b=BjOHNqMW8tr1vyRnduG/FJYKr0WUjjhsS+3FDHanx1rCc7dSVIAJGY1b/l2Uw0v5xK Qc3+iDP+bSOLRtXr77SQJMzE1sXwom4e+efkO5uusadZEXzSWwaUZbHB80lr4jAg3liu uxyXd88o7hE9nxl8TqUCvhhGe1RF7CWl6YdK8Ori4peBVVxy1f4LVbL0G5N5YuiFTX+r b+U3/HQDCChqZhsRPpmVguI4pepL5aZUG2C0hc6Fp4mxkJgovAlK2OQ0SEXz5aKO+W0b /8QNpbI0f8ioJtXgaEOYzvaRs7RqEDVnlGTcwWQ/RRKLOthooM4eobg1rgclYWGfdirI iMCg== 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=zhpzHaewQiFA7zyinksagIouSrpHytz8zX+SwMrxXA0=; b=uzVT9MJs6cEazvJARrJzIt8Hfbcl5j1prYMNMvfgcWt4UUTNPq7DGKElQIfkFlX4sm uWFhcEwelnwlgmWE28HgvE5sjYTFQT32nnFQj14eHKOBgMBb+vvITrkm8o1rQ17ltuij tAN3qr7Dqi75WmY+504elFSt46irbegpH1JqQJOOqiEdEe84r1c5AGILrAJf6BxweJ43 CLeZUTIarv3mK+gfewYt2flH1br9PxOLdUXSv0P6zaV9DhM2WrJupmY9vfUxGEuorhwb glujWGKrgv6AyvNiG9bdAapUkMVl1D4+iawF0CZ2f662fhjE0q2VhszLyZE2lhDGyl/P yIhw== X-Gm-Message-State: AOAM530C/Erw1V59WlEZh2d2tantpDdwiYcOK0Z/zmFU/Bf6zay2EcwY uKtWgBCgvO6qxdz8XQPfEfo= X-Google-Smtp-Source: ABdhPJyIQK3QWEjDfNixvk999ZO5keQTyNoa+LCHUl+gYfJdtGkWE9yV4QCwA3+i+HabIF6ZlDLeLw== X-Received: by 2002:a63:2049:0:b0:381:31b6:a317 with SMTP id r9-20020a632049000000b0038131b6a317mr3200637pgm.356.1648296058041; Sat, 26 Mar 2022 05:00:58 -0700 (PDT) Received: from localhost.localdomain ([114.200.4.15]) by smtp.gmail.com with ESMTPSA id b16-20020a056a00115000b004f6ff260c9esm9373956pfm.207.2022.03.26.05.00.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 26 Mar 2022 05:00:57 -0700 (PDT) Date: Sat, 26 Mar 2022 21:00:51 +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> <20220324103056-mutt-send-email-mst@kernel.org> <20220324135556-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220324135556-mutt-send-email-mst@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Thu, Mar 24, 2022 at 01:56:18PM -0400, Michael S. Tsirkin wrote: > On Thu, Mar 24, 2022 at 11:46:02PM +0900, Suwan Kim wrote: > > On Thu, Mar 24, 2022 at 10:32:02AM -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); > > > > > > > > > > Is there some way to make it work reasonably without need to set > > > module parameters? I don't see any other devices with a num_poll_queues > > > parameter - how do they handle this? > > > > Hi Michael, > > > > NVMe driver uses module parameter. > > > > Please refer to this. > > ----- > > drivers/nvme/host/pci.c > > > > static unsigned int poll_queues; > > module_param_cb(poll_queues, &io_queue_count_ops, &poll_queues, 0644); > > MODULE_PARM_DESC(poll_queues, "Number of queues to use for polled IO."); > > ----- > > > > Regards, > > Suwan Kim > > OK then. Let's maybe be consistent wrt parameter naming? Ok. Consistent naming scheme seems to be better for code readability. I will rename it to 'poll_queues' in next version. Regards, Suwan Kim