From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20230601.gappssmtp.com header.i=@kernel-dk.20230601.gappssmtp.com header.b="R1dbJvL4" Received: from mail-pj1-x1029.google.com (mail-pj1-x1029.google.com [IPv6:2607:f8b0:4864:20::1029]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C0DE810DE for ; Thu, 7 Dec 2023 19:15:20 -0800 (PST) Received: by mail-pj1-x1029.google.com with SMTP id 98e67ed59e1d1-2886d445d8dso402726a91.1 for ; Thu, 07 Dec 2023 19:15:20 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20230601.gappssmtp.com; s=20230601; t=1702005320; x=1702610120; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=jGfLZ/anCgoizin3EJrsBtWsOUnIV8oEkhHw3KAoiyE=; b=R1dbJvL4+eLjEhhg0VgKY1AyJG3WfUpl2uxQt+FrXUBP2zJo3ZTU1KPTLIGLtnpSvl WVtby8UN9DTj5oBxNmDlOmfjSz+86PVJOXQ5XTk+0QOpU32ClIiM52GlRRfnjv+o2wTL FJ7mn4tve4W+KE7AhVjKoQ3JwmfPod4VQDdS0O8aO+OdAlidD2cS5xY04gE/Ncwb52Wv s6PoYDk+M7xrGj8YUaBpbUjLRNaqZsqHilmMLjBcI2UZhYP9cXdprcq/USkp3IGdSp3p aJoJSuaraEW1cwQgBvbsqF0FH/fjvDJWvCwZzNPe5TpdyvDb/0JOGMriSqLcnHEEKCuR Jz8w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1702005320; x=1702610120; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=jGfLZ/anCgoizin3EJrsBtWsOUnIV8oEkhHw3KAoiyE=; b=IxbXLczcpNzCQwdqWgAYfLDIaUcP52/Un8Fa5L9BfrBx2QwNMW/Hzv9sC5+zEdWhT8 ImeAXnb5NYiwolza5NupMsqAMmKTc/CzpvoO+S037MmTp0SIfBoGo5xZ7YGu9VYEvNpq FSl/lJUZAxgn19fjKs0Be+lwfHHY1S1sbMQxQDcNNZOmCIACeuUjMgm18LGuVcJe8I3o AwMQLg4+rRw4Fqb+cWjaJxkZOvvcVGU1RoRuxPgRpzcXYX5z91mBNjI+DY/sUce72BC5 NbC0dGXxLNTUSo8Ucm1tlNSmJPdO0ivnm16MYmCJ8ROPPoQCx+yqH4pk6lTEiSzuNtfn LnMg== X-Gm-Message-State: AOJu0YzzE0GEEVPuwN0dze5OnH4A4G/x6AECt8+M8lG2LzF/NlYBLa9a MbrAgrnsjij23kWuGBBr6oPTeg== X-Google-Smtp-Source: AGHT+IEb0VGLsYlBNxLkCRq834nrTlhul/JW2q5GdSZUzgMVZYylVw6G7cr3f6N2ts4MFxlhZfZU8A== X-Received: by 2002:a05:6a20:1583:b0:18b:4b84:3a1 with SMTP id h3-20020a056a20158300b0018b4b8403a1mr7015450pzj.5.1702005320251; Thu, 07 Dec 2023 19:15:20 -0800 (PST) Received: from [192.168.1.150] ([198.8.77.194]) by smtp.gmail.com with ESMTPSA id w4-20020aa78584000000b006ce5c583c89sm532425pfn.15.2023.12.07.19.15.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 07 Dec 2023 19:15:19 -0800 (PST) Message-ID: Date: Thu, 7 Dec 2023 20:15:18 -0700 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] virtio_blk: set the default scheduler to none Content-Language: en-US To: Keith Busch , Ming Lei Cc: Li Feng , "Michael S. Tsirkin" , Jason Wang , Paolo Bonzini , Stefan Hajnoczi , Xuan Zhuo , "open list:BLOCK LAYER" , open list , "open list:VIRTIO BLOCK AND SCSI DRIVERS" References: <20231207043118.118158-1-fengli@smartx.com> From: Jens Axboe In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 12/7/23 7:44 PM, Keith Busch wrote: > On Fri, Dec 08, 2023 at 10:00:36AM +0800, Ming Lei wrote: >> On Thu, Dec 07, 2023 at 12:31:05PM +0800, Li Feng wrote: >>> virtio-blk is generally used in cloud computing scenarios, where the >>> performance of virtual disks is very important. The mq-deadline scheduler >>> has a big performance drop compared to none with single queue. In my tests, >>> mq-deadline 4k readread iops were 270k compared to 450k for none. So here >>> the default scheduler of virtio-blk is set to "none". >> >> The test result shows you may not test HDD. backing of virtio-blk. >> >> none can lose IO merge capability more or less, so probably sequential IO perf >> drops in case of HDD backing. > > More of a curiosity, as I don't immediately even have an HDD to test > with! Isn't it more useful for the host providing the backing HDD use an > appropriate IO scheduler? virtio-blk has similiarities with a stacking > block driver, and we usually don't need to stack IO schedulers. Indeed, any kind of scheduling or merging should not need to happen here, but rather at the lower end. But there could be an argument to be made for having fewer commands coming out of virtio-blk, however. Would be interesting to test. -- Jens Axboe