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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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9b46c48f-d7c4-4ed3-a644-fba90850eab8@acm.org> X-Rspamd-Queue-Id: 96C7A20009 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: urhqniqt13s41mpzdxwz8eihpfp3o5aq X-HE-Tag: 1704742528-776071 X-HE-Meta: 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 6ga2FQf5 D9pXIqSANc2XcN+XQaB2pSnMXDhO2P1mcQY2dSQOudrY9Dexk1qZenosFRX/QbVdBCl80WEWylDctNlaspI3SUZfuARKoLYr2hViMS0NlwKgkwGp8meChjDFVbT5lxxIYKxIECafSjV/lBlyVz7CnCCbShuoLUvoJWRdqW+cPLEwV0nEAicVzLrMxMA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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.