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 E51D4C433EF for ; Thu, 24 Mar 2022 14:46:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235849AbiCXOrm (ORCPT ); Thu, 24 Mar 2022 10:47:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51746 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348500AbiCXOrl (ORCPT ); Thu, 24 Mar 2022 10:47:41 -0400 Received: from mail-pl1-x62d.google.com (mail-pl1-x62d.google.com [IPv6:2607:f8b0:4864:20::62d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DF1FCAA02A for ; Thu, 24 Mar 2022 07:46:09 -0700 (PDT) Received: by mail-pl1-x62d.google.com with SMTP id e5so4909580pls.4 for ; Thu, 24 Mar 2022 07:46:09 -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=WISKDUteM5NcAOm1Q8SPPpsBI0zUWDomUyUHIXbTjJE=; b=GILWGvN/EjRWdY+Y0SN7oCw8g23m0sHKSHghLFT2fYac3k6OsXmJugTMK0QuILZGjS 3PzbIRHZegVqXjLf3D1dJSx4KFNMt0eiqpoJN2m0ypLI0EJjMyVf+y74fzw+F8gk01jr dJRxPAYyk+fgrHIlv2gYdskDKobEaKKce+/V5NKJ8IebionxAMwe6C0Js/Q+SWx0d2bG tE+RN6mb8WYVGyCPqGTiFfdyICydBxhCbzjUfLL10deUPlux3oY6u5WwmMcsPnmtWOJa UCDbIItsBcHP7CvVxEfbQ0ykZvFZghnfvOXSLND9VY0WRlwlei8fHJYl0wRuJL6uXl7q Lg+A== 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=WISKDUteM5NcAOm1Q8SPPpsBI0zUWDomUyUHIXbTjJE=; b=GZPG+vj7WS2Xys7AAw47CSDquuChO4IkNVu4fUbmsSrPwOSnraszjxD6FK/TDLxxqt Ya+SYsfMNgZwwvF7QgbbOGSgWHRSnGxQqWCP/UAb6TE506HWRhPhhopVuSP083h4pZTq Hm19/VqHGHB2jy0p9S8TANffvJqZ+WSRGsRKy3YDg7PjlfHW9y4M6hvgwXgozwHHBRjR BlINz10QUqRueySLWM9NRCUoGKI8+6mVb1LvrXvlB3zQgb3wPDliF8JOmG5ORNKWjZUf wHC6BSow9gzf6iqF14LCfYjYyKH4KlltjYe8ohPeJUVG3QQOaS2SvpUG/rP3YFewvRO2 mlhw== X-Gm-Message-State: AOAM53353w9y+IWQ76NOBMgAReqOx8rdaaBOwE7esO+CguqMhxpbyXMZ TQGf0MZxW6fVlX1OOGwpKzM= X-Google-Smtp-Source: ABdhPJx4AmitG5S3OXAp8ZnRhZsx/mdg2jp4kTRu0Uf32son+v7C+FVhTDQBq2qQnE2B7X0p97NElw== X-Received: by 2002:a17:902:ce8c:b0:154:af35:381e with SMTP id f12-20020a170902ce8c00b00154af35381emr6353303plg.144.1648133169322; Thu, 24 Mar 2022 07:46:09 -0700 (PDT) Received: from localhost.localdomain ([114.200.4.15]) by smtp.gmail.com with ESMTPSA id p10-20020a637f4a000000b00373a2760775sm2874348pgn.2.2022.03.24.07.46.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 24 Mar 2022 07:46:08 -0700 (PDT) Date: Thu, 24 Mar 2022 23:46:02 +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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220324103056-mutt-send-email-mst@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org 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