From patchwork Mon Aug 19 18:17:29 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Mike Snitzer X-Patchwork-Id: 13768793 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 E669A18B46F; Mon, 19 Aug 2024 18:18:24 +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=1724091505; cv=none; b=JgPxeaz1+DHVrZIFemZKdnrqXO4SBWK5h96uByMKLbacOp7lmUhHFonOia/8HJv0WifPG1gzuoCtSylOS1cJ9HhwmZXOPCOPowtN9PoIbT5ObxF+ruDaqbNM18lHHqqF4BVU8N+0ltLuTccAsxWSWpfOsSjdDOMW6aNDDMB2/Hk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724091505; c=relaxed/simple; bh=aG9IkFvVW3wIWK9Qnp3warZ9GiIWNMtEp7QTQUr9qZI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=JMvxIFP/XUNL8YhptOOCJ3DOypO0n6sEEzpkCtA8yEey6/UQdUZHHG+1pDHI28LwBPsxIW0vXvKYJmLaUAM3GzBGLpt+0cPDZlCBwDtLrHuJB3Iftg78klwHOodLUTRafU163vv64sgF2SFstQ97YfBBZRMjydBSf+gYVMUfT7E= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=WDpBRHwF; 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="WDpBRHwF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8D4BBC32782; Mon, 19 Aug 2024 18:18:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1724091504; bh=aG9IkFvVW3wIWK9Qnp3warZ9GiIWNMtEp7QTQUr9qZI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WDpBRHwFbFp35p3Vz11Qx1anmLA4P3Hnh8cgYNW1icI6Tejqx1cyIcbMPZTk3SuMh uba5v5cTxOi8Nz8EaH1PdXfezlzNF78MyJnLVFg4WJpmfEzoeckwwIQ5MVRh9/gy1K Xc19mc0b9UPIkVhs+23/PciFItUiiDZ1n65k2ZqdM/eOAdFpeOSHxV4LXJ3HdH8d32 dk5h65ow1Z1DONjMi2nt1QudCeqnMu4YycvUfDdJAVmWCQrrq3SCp18t0Mf+rAiJ77 T8pdASvoN6V3MsRqO01RdGrdN+fz7445dN6G59B5SqGgmRehYCTY1XZUmjMENUsgCN kX/31aS+tioqw== 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 v12 24/24] nfs: add FAQ section to Documentation/filesystems/nfs/localio.rst Date: Mon, 19 Aug 2024 14:17:29 -0400 Message-ID: <20240819181750.70570-25-snitzer@kernel.org> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240819181750.70570-1-snitzer@kernel.org> References: <20240819181750.70570-1-snitzer@kernel.org> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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 | 77 +++++++++++++++++++++++ 1 file changed, 77 insertions(+) diff --git a/Documentation/filesystems/nfs/localio.rst b/Documentation/filesystems/nfs/localio.rst index d8bdab88f1db..acd8f3e5d87a 100644 --- a/Documentation/filesystems/nfs/localio.rst +++ b/Documentation/filesystems/nfs/localio.rst @@ -40,6 +40,83 @@ fio for 20 secs with 24 libaio threads, 128k directio reads, qd of 8, - Without LOCALIO: read: IOPS=12.0k, BW=1495MiB/s (1568MB/s)(29.2GiB/20015msec) +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. However adding a + requirement to go over the wire to do an open and/or close ends up + negating any benefit of avoiding the wire for doing the I/O itself + when we’re dealing with small files. There is no benefit to replacing + the READ or WRITE with a new open and/or close operation that still + needs to go over the wire. + +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 ===