From patchwork Thu Aug 29 01:47:09 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Mike Snitzer X-Patchwork-Id: 13782389 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 E879F25777; Thu, 29 Aug 2024 01:47:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724896031; cv=none; b=P9GiCFNueNT7cdatel4DXh46zGU0nh01TAoBccF60luxw/ze2mk/EuYL3fbauaAIoQGc1MCDtnG/0kiv5T49RAaDtLKr7x1iufjQF+fFVSR/fZGJxdamU0Bj0zUwFBCFT1+fkGvICOx1fQBKur4JhUEpQ1OrEYhtldc6WedNWl8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724896031; c=relaxed/simple; bh=rX03S+qYQPU1f9W/MD3wNiLX4lQKlgxcmGgXmzT6Ne0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=GIWESaFxfrTUNoSNix7ZZbaGwIIKFcbQD88tDuNBP4fWKWaaGluE7s01F8yRJYSOXFMhyzii4fr9qW7uqZBZ3dcozrOXV2O7Vb5m0NWDmFByp0JZZ8CKX2q1MGVaCC6uutOH+ZuKQfDc//5rUUMCuaqEmpYKf79vf0vCv4hVSxU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fXBQ4p3k; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="fXBQ4p3k" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2DD4BC4CEC0; Thu, 29 Aug 2024 01:47:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1724896030; bh=rX03S+qYQPU1f9W/MD3wNiLX4lQKlgxcmGgXmzT6Ne0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=fXBQ4p3ktBRLq7SEpdbXhGgT7GPvyh1zLlAwqR4UvEI86b6ibrG72EUyGX2HkyCp3 BFK/kAboOP/JXM4GXm/0keHm4S40ouDBFRwBpLJ8xwXbk5HnwnkygPC16uH8iBVD/t BsMBsUKtLuaj1ykoojBb/2WMe+FstGQAhNpSN935VEK5y+fIh+xKjYS3dcWWGofeP5 ULm1WkUrVDmEFVexFQri3Q9w+GukdXWxkLNnXJWHO/9R4uidYi6J5QycarXaIEm3Ic +TdaSrcKy6tYZBR70hhcFail28FM8LNoqUl2mIzaES+B2+Tp/OzUfr4/QUY+bbWLlp x/gwAS5YWqmtQ== Date: Wed, 28 Aug 2024 21:47:09 -0400 From: Mike Snitzer To: linux-nfs@vger.kernel.org Cc: Jeff Layton , Chuck Lever , Anna Schumaker , Trond Myklebust , NeilBrown , linux-fsdevel@vger.kernel.org Subject: [PATCH v14.5 25/25] nfs: add FAQ section to Documentation/filesystems/nfs/localio.rst Message-ID: References: <20240829010424.83693-1-snitzer@kernel.org> <20240829010424.83693-26-snitzer@kernel.org> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20240829010424.83693-26-snitzer@kernel.org> From: Trond Myklebust Add a FAQ section to give answers to questions that have been raised during review of the localio feature. Signed-off-by: Trond Myklebust Co-developed-by: Mike Snitzer Signed-off-by: Mike Snitzer --- Documentation/filesystems/nfs/localio.rst | 78 +++++++++++++++++++++++ 1 file changed, 78 insertions(+) diff --git a/Documentation/filesystems/nfs/localio.rst b/Documentation/filesystems/nfs/localio.rst index 8cceb3db386a..5d652f637a97 100644 --- a/Documentation/filesystems/nfs/localio.rst +++ b/Documentation/filesystems/nfs/localio.rst @@ -61,6 +61,84 @@ fio for 20 secs with directio, qd of 8, 1 libaio thread: 128K read: IOPS=24.4k, BW=3050MiB/s (3198MB/s)(59.6GiB/20001msec) 128K write: IOPS=11.4k, BW=1430MiB/s (1500MB/s)(27.9GiB/20001msec) +FAQ +=== + +1. What are the use cases for LOCALIO? + + a. Workloads where the NFS client and server are on the same host + realize improved IO performance. In particular, it is common when + running containerised workloads for jobs to find themselves + running on the same host as the knfsd server being used for + storage. + +2. What are the requirements for LOCALIO? + + a. Bypass use of the network RPC protocol as much as possible. This + includes bypassing XDR and RPC for open, read, write and commit + operations. + b. Allow client and server to autonomously discover if they are + running local to each other without making any assumptions about + the local network topology. + c. Support the use of containers by being compatible with relevant + namespaces (e.g. network, user, mount). + d. Support all versions of NFS. NFSv3 is of particular importance + because it has wide enterprise usage and pNFS flexfiles makes use + of it for the data path. + +3. Why doesn´t LOCALIO just compare IP addresses or hostnames when + deciding if the NFS client and server are co-located on the same + host? + + Since one of the main use cases is containerised workloads, we cannot + assume that IP addresses will be shared between the client and + server. This sets up a requirement for a handshake protocol that + needs to go over the same connection as the NFS traffic in order to + identify that the client and the server really are running on the + same host. The handshake uses a secret that is sent over the wire, + and can be verified by both parties by comparing with a value stored + in shared kernel memory if they are truly co-located. + +4. Does LOCALIO improve pNFS flexfiles? + + Yes, LOCALIO complements pNFS flexfiles by allowing it to take + advantage of NFS client and server locality. Policy that initiates + client IO as closely to the server where the data is stored naturally + benefits from the data path optimization LOCALIO provides. + +5. Why not develop a new pNFS layout to enable LOCALIO? + + A new pNFS layout could be developed, but doing so would put the + onus on the server to somehow discover that the client is co-located + when deciding to hand out the layout. + There is value in a simpler approach (as provided by LOCALIO) that + allows the NFS client to negotiate and leverage locality without + requiring more elaborate modeling and discovery of such locality in a + more centralized manner. + +6. Why is having the client perform a server-side file OPEN, without + using RPC, beneficial? Is the benefit pNFS specific? + + Avoiding the use of XDR and RPC for file opens is beneficial to + performance regardless of whether pNFS is used. Especially when + dealing with small files its best to avoid going over the wire + whenever possible, otherwise it could reduce or even negate the + benefits of avoiding the wire for doing the small file I/O itself. + Given LOCALIO's requirements the current approach of having the + client perform a server-side file open, without using RPC, is ideal. + If in the future requirements change then we can adapt accordingly. + +7. Why is LOCALIO only supported with UNIX Authentication (AUTH_UNIX)? + + Strong authentication is usually tied to the connection itself. It + works by establishing a context that is cached by the server, and + that acts as the key for discovering the authorisation token, which + can then be passed to rpc.mountd to complete the authentication + process. On the other hand, in the case of AUTH_UNIX, the credential + that was passed over the wire is used directly as the key in the + upcall to rpc.mountd. This simplifies the authentication process, and + so makes AUTH_UNIX easier to support. + RPC ===