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="Fvt1xH21" Received: from mail-il1-x12e.google.com (mail-il1-x12e.google.com [IPv6:2607:f8b0:4864:20::12e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 17488A7 for ; Mon, 27 Nov 2023 08:10:06 -0800 (PST) Received: by mail-il1-x12e.google.com with SMTP id e9e14a558f8ab-35ca48d48f1so1715075ab.1 for ; Mon, 27 Nov 2023 08:10:06 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20230601.gappssmtp.com; s=20230601; t=1701101405; x=1701706205; 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=ZtIIccdhs8yz+yiJjCrLMyK2ZFy1CQEPmm7PUbEVf7I=; b=Fvt1xH210eU0Tp6AOVG5kL42g89qbCU+v3xMkVldRwz+w+SyT4sF2gTig63NG9An8w 6XWxuhEmN/72kDT1VUjR8y2s7fBgFn6s4mkj652xAYasd7M0NoXsJs//fn1edF6Hy3ZN gX7HZDfcdR2/77zDc28YvedHmqUCgX6kiHYeoZMLPURqxb1cE015hArO7KB7DTCyt+5H WmSEbypw504TG4kTwmlTbx3kC1o9v4YjteytrqBUxOaEdy+qUk2D5ofW47dwCa1Y5aKO dzNSR05NZ1xKC3BrQf6uZ/yPI1AnawH3hgB10ikfgUwAglfJZ7WVGqBFRd+bMv+tK1pl tTqA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1701101405; x=1701706205; 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=ZtIIccdhs8yz+yiJjCrLMyK2ZFy1CQEPmm7PUbEVf7I=; b=ZNVipKHlAnJHTZLFXd2s0bGLZ1y9qS9655Kw1P59E2QMR0ewZqV3EkFYgnWeKnTzCy QOFPmsWOu06AZBG0Vp5O02aMaqTD4f56dzBxVgpA+DB3hNzKWFAdbrrE+8loFl8vP044 UxZUbL3X7tuWSY9zwwB6o/G8oaBRF/rVewW/W7vEqo5TJQEW8Tq9LClUt4DGCTxqh+Xk R8+jp0lHbWwcB3+YTThPbkz31U5bOqy9uxdcDqYAbY5cO4pF4+6MiQZSOfH3QZrvJzgs 8qMqyMr2Lk6mSN3/MItMO+7wqJL+s/JtNUA/g4z+LshW9EqIDvWfnBXISCcis1R/j9zJ /kqQ== X-Gm-Message-State: AOJu0YzOpuhmZrbbb2r3U1OSy9/IGEcLiWBgCKr3yK6xJ2+kjYpgbUnA cawjQp2gdryqkiyZMMY8aWzTSXhthap/PQdKtdQQRg== X-Google-Smtp-Source: AGHT+IG/IaqyGyROu7hEZKzZJuUB5m4Skn6QbtiicnN+TWTrcKiqLe/Y3pmcCOuwBT1U4spu+VXwcQ== X-Received: by 2002:a05:6602:489a:b0:7b3:95a4:de9c with SMTP id ee26-20020a056602489a00b007b395a4de9cmr6090167iob.1.1701101405357; Mon, 27 Nov 2023 08:10:05 -0800 (PST) Received: from [192.168.1.116] ([96.43.243.2]) by smtp.gmail.com with ESMTPSA id c24-20020a05660221d800b007870289f4fdsm2459925ioc.51.2023.11.27.08.10.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Nov 2023 08:10:04 -0800 (PST) Message-ID: Date: Mon, 27 Nov 2023 09:10:03 -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: Merging raw block device writes Content-Language: en-US To: "hch@lst.de" , Michael Kelley Cc: "linux-block@vger.kernel.org" , "linux-hyperv@vger.kernel.org" References: <20231127065928.GA27811@lst.de> From: Jens Axboe In-Reply-To: <20231127065928.GA27811@lst.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/26/23 11:59 PM, hch@lst.de wrote: > On Sat, Nov 25, 2023 at 05:38:28PM +0000, Michael Kelley wrote: >> Hyper-V guests and the Azure cloud have a particular interest here >> because Hyper-V guests uses SCSI as the standard interface to virtual >> disks. Azure cloud disks can be throttled to a limited number of IOPS, >> so the number of in-flights I/Os can be relatively high, and >> merging can be beneficial to staying within the throttle >> limits. Of the flip side, this problem hasn't generated complaints >> over the last 18 months that I'm aware of, though that may be more >> because commercial distros haven't been running 5.16 or later kernels >> until relatively recently. > > I think the more important thing is that if you care about reducing > the number of I/Os you probably should use an I/O scheduler. Reducing > the number of I/Os without an I/O scheduler isn't (and I'll argue > shouldn't) be a concern for the non I/O scheduler. Yep fully agree. -- Jens Axboe