From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 E009C17C68 for ; Sat, 6 Jul 2024 06:42:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720248152; cv=none; b=FefeRyTJbEzqoR9H5zDXsy0kzHwLHsSCvZ1NtY+ISPMjFsC05mvZ/L/VmkjJRs5987HcB17emhHItwzPdSRf2DQ8K/cO9W8H27+cTqkr+O8N7sRlC78022WLuwCgSgXRR8AeaVML3IcE0Sb3iP4duUOO0SlFqXWhV1vFkdDWmEE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720248152; c=relaxed/simple; bh=pbRHl0ZA6GoE99YYTQAj6lyXLTKhJUgYvqTyMDh3TD8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=hr2lvduyOfCMgaU8QtJeyCZOsx3HgBLUOKxXre7K3l1EKrq9N2JxGKYcpYBAfOj/pBk/dQkLfLu7QleEuVTF0zMmd8X1ehd63cltSYyw5Pd0C/ocJtf3U6WOSAsFfINMWyurMHaEm8OB3/MofWu7nVCZDAVV9q5va/3C+TkbXCc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=dDuok2VG; arc=none smtp.client-ip=198.137.202.133 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=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="dDuok2VG" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; 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=zUZt5tObI5Xb1kCTAv2Q8zq8Y7pJw8jQQnC1nGNPzAE=; b=dDuok2VGTWcpnSRC9rPjwmXOWp y/lctArFfM4XZkf7y3eoNB/3kC6kHsZqjxvFlbG3DQQWCsKSZfIZ5R8BvyG/1r3Sg07Tnzag9gh4L 2EePYWaBeqqipxWFumrZGO/hCPXUhFjBqTZTQ35mi/8Kbqi4Jy1Dt0xSI2/bV7LnZlcCw+gK5B91f 7Vg3lYd30VosExH9sYoIseR2GFu3XP9MUIpWu98IefEBrARHQI2vFbRP5mFMVJUMvZ5ovfmMPvd8m WAH8sHpUmrlCmEHV9FtR/TsyADNCLRpOEQzhUKXo4dmSAihHMw6QaIWhDWa8pCp2CjgYrfbNHV+Is 3pejvFQA==; Received: from hch by bombadil.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1sPz7t-0000000HQgv-3xgF; Sat, 06 Jul 2024 06:42:29 +0000 Date: Fri, 5 Jul 2024 23:42:29 -0700 From: Christoph Hellwig To: NeilBrown Cc: Christoph Hellwig , Mike Snitzer , Jeff Layton , Chuck Lever III , Linux NFS Mailing List , Anna Schumaker , Trond Myklebust , Dave Chinner Subject: Re: [PATCH v11 00/20] nfs/nfsd: add support for localio Message-ID: References: <> <172024784245.11489.13308466638278184214@noble.neil.brown.name> Precedence: bulk X-Mailing-List: linux-nfs@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: <172024784245.11489.13308466638278184214@noble.neil.brown.name> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Sat, Jul 06, 2024 at 04:37:22PM +1000, NeilBrown wrote: > > a different scheme for bypassing the server for I/O. Maybe there is > > a really good killer argument for doing that, but it needs to be clearly > > stated and defended instead of assumed. > > Could you provide a reference to the text book - or RFC - that describes > a pNFS DS protocol that completely bypasses the network, allowing the > client and MDS to determine if they are the same host and to potentially > do zero-copy IO. I did not say that we have the exact same functionality available and there is no work to do at all, just that it is the standard way to bypass the server. RFC 5662, RFC 5663 and RFC 8154 specify layouts that completely bypass the network and require the client and server to find out that they talk to the same storage devuce, and directly perform zero copy I/O. They do not require to be on the same host, though. > If not, I will find it hard to understand your claim that it is "the > text book example". pNFS is all about handing out grants to bypass the server for I/O. That is exactly what localio is doing.