From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; dkim=none Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C4F2B13D; Sun, 26 Nov 2023 22:59:31 -0800 (PST) Received: by verein.lst.de (Postfix, from userid 2407) id 968A268AFE; Mon, 27 Nov 2023 07:59:28 +0100 (CET) Date: Mon, 27 Nov 2023 07:59:28 +0100 From: "hch@lst.de" To: Michael Kelley Cc: "axboe@kernel.dk" , "hch@lst.de" , "linux-block@vger.kernel.org" , "linux-hyperv@vger.kernel.org" Subject: Re: Merging raw block device writes Message-ID: <20231127065928.GA27811@lst.de> References: Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) 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.