From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E73CE5380C; Mon, 8 Jan 2024 19:35:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="v7UTSp5y" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=/CnY1WrNa6ivAwOul4iLunYaBF0zr/21B1/t616St8k=; b=v7UTSp5yHaxoKw/l6drPxI8TGd eEQOGfG75PN/u2R8GCSiFXX8/FgIcyz4FeOiqy4Qn1DmN53Lddq27eJPNPHHSau2g22qhNvLBydfL omZZQVQV435kP8cVkuKkuBY2Q1kxjCnneG1EcdW34GP0MWJXxP1CMOEo5KhxmLf7fcMhEICOVmRR0 kCq3gh8g+lvK4JFhi+QT1z0fjI4nASTHvtHk1roiqnhdoxYYexx4LwPVqbnabGYHHntbifHaWDIWR M/diELIjTfwbx0tvVBCsP4MejbaeK0NBagqRQ2bnIUuBVluAnx2kWtTGZ5/nIBdpJP1VDUVWbRpV1 iXZ5dKVA==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1rMvP3-008I9G-Ol; Mon, 08 Jan 2024 19:35:17 +0000 Date: Mon, 8 Jan 2024 19:35:17 +0000 From: Matthew Wilcox To: Bart Van Assche Cc: Christoph Hellwig , Hannes Reinecke , lsf-pc@lists.linuxfoundation.org, linux-mm@kvack.org, linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, "linux-nvme@lists.infradead.org" Subject: Re: [LSF/MM/BPF TOPIC] Large block for I/O Message-ID: References: <7970ad75-ca6a-34b9-43ea-c6f67fe6eae6@iogearbox.net> <4343d07b-b1b2-d43b-c201-a48e89145e5c@iogearbox.net> <03ebbc5f-2ff5-4f3c-8c5b-544413c55257@suse.de> <5c356222-fe9e-41b0-b7fe-218fbcde4573@acm.org> <9b46c48f-d7c4-4ed3-a644-fba90850eab8@acm.org> Precedence: bulk X-Mailing-List: linux-scsi@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: <9b46c48f-d7c4-4ed3-a644-fba90850eab8@acm.org> On Mon, Jan 08, 2024 at 11:30:10AM -0800, Bart Van Assche wrote: > On 12/21/23 21:37, Christoph Hellwig wrote: > > On Fri, Dec 22, 2023 at 05:13:43AM +0000, Matthew Wilcox wrote: > > > It clearly solves a problem (and the one I think it's solving is the > > > size of the FTL map). But I can't see why we should stop working on it, > > > just because not all drive manufacturers want to support it. > > > > I don't think it is drive vendors. It is is the SSD divisions which > > all pretty much love it (for certain use cases) vs the UFS/eMMC > > divisions which tends to often be fearful and less knowledgeable (to > > say it nicely) no matter what vendor you're talking to. > > Hi Christoph, > > If there is a significant number of 4 KiB writes in a workload (e.g. > filesystem metadata writes), and the logical block size is increased from > 4 KiB to 16 KiB, this will increase write amplification no matter how the > SSD storage controller has been designed, isn't it? Is there perhaps > something that I'm misunderstanding? You're misunderstanding that it's the _drive_ which gets to decide the logical block size. Filesystems literally can't do 4kB writes to these drives; you can't do a write smaller than a block. If your clients don't think it's a good tradeoff for them, they won't tell Linux that the minimum IO size is 16kB. Some workloads are better with a 4kB block size, no doubt. Others are better with a 512 byte block size. That doesn't prevent vendors from offering 4kB LBA size drives.