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 B14B613C695; Thu, 20 Mar 2025 12:11:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742472717; cv=none; b=ZeZpKxfxVOqMSI3HrMJfREts5Czfw9t+QVtGlh8r1bNvTbOUAuNzX77dkiJi7zmwnNHW47JveGaDdgTgM5LScHMsAh+5eEt/VZ56HmSBMZHvJVchonEqbCGYduviHFvPsxoVmJenDBdW3+uKz05zwoh5H3bqyFd2k0onmx1LwtM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742472717; c=relaxed/simple; bh=K3hg1bCjJiCU739YdKYncHOb2k8F152AweW3t/yo/+k=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=fYPiQlnb6jcwyOtpOzn9kwpKi2Awhm3kd8WBENiEjesdghWgmd6dvaqpj1YBBElLtHFIzLW1SoNlJyjlX/mZ7d0FLu0W9DSPbzhkYSbFLTxrIUgrXOQPzovyUnNKz05ri+DkmWEYhcFIcdZ2ueoyTVIgA7HvC+JFXYOTLXr8wA8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=CYrG33lH; arc=none smtp.client-ip=90.155.50.34 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="CYrG33lH" 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=6GdYJvaUyHN33OWPLsIOGOvCIvn/uOWWV0lLG312V8w=; b=CYrG33lHZUSnxCeeDL6buuQ3Gd ZXncxZYgvDt1AhMNMoxH0NNgwN2Vl/F9DMX+klnY+ql1Nb+wF/bNYyP/5zrijkmvfvPDldi/G/EXp KZ1Q1NnN3Rr8W5nTujHbkt3VZiKIH9ixxUui/KKTA3xtFqsZfx5lXXPq5W6wTx/2lpL8sWXxZKC4J TOdTSyTLt3BwtjJhMpAK7cx44jaEMtN5u4ZeVbRBcNzwzpAjKmCKA3scFSbMAUkwwPWRaK1TbSfTT ixPtmOV+j6xVtlwvDjX1uEPVjP7nTjGExNuYoIeZyhvmcGgOTeQaTXbjfMIkvYPuLHAk9OrzT0L5s orBbgBbA==; Received: from willy by casper.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tvEkV-0000000A7g4-2x1Q; Thu, 20 Mar 2025 12:11:47 +0000 Date: Thu, 20 Mar 2025 12:11:47 +0000 From: Matthew Wilcox To: Luis Chamberlain Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-block@vger.kernel.org, lsf-pc@lists.linux-foundation.org, david@fromorbit.com, leon@kernel.org, hch@lst.de, kbusch@kernel.org, sagi@grimberg.me, axboe@kernel.dk, joro@8bytes.org, brauner@kernel.org, hare@suse.de, djwong@kernel.org, john.g.garry@oracle.com, ritesh.list@gmail.com, p.raghav@samsung.com, gost.dev@samsung.com, da.gomez@samsung.com Subject: Re: [LSF/MM/BPF TOPIC] breaking the 512 KiB IO boundary on x86_64 Message-ID: References: Precedence: bulk X-Mailing-List: linux-fsdevel@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: On Thu, Mar 20, 2025 at 04:41:11AM -0700, Luis Chamberlain wrote: > We've been constrained to a max single 512 KiB IO for a while now on x86_64. ... > It does beg a few questions: > > - How are we computing the new max single IO anyway? Are we really > bounded only by what devices support? > - Do we believe this is the step in the right direction? > - Is 2 MiB a sensible max block sector size limit for the next few years? > - What other considerations should we have? > - Do we want something more deterministic for large folios for direct IO? Is the 512KiB limit one that real programs actually hit? Would we see any benefit from increasing it? A high end NVMe device has a bandwidth limit around 10GB/s, so that's reached around 20k IOPS, which is almost laughably low.