From patchwork Thu Aug 29 01:04:20 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Mike Snitzer X-Patchwork-Id: 13782341 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 24E2C14A0A3; Thu, 29 Aug 2024 01:04:59 +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=1724893500; cv=none; b=ToF3qa5OlI0DKNZ8ICI3vLwUsCCCeC3FcYz2sziiyc6vTGtVDg0uXv+qTTrnOUnmvtDqL9IIFilcTSejKPu3RK788hm25hjxca/bmmj2sK2VvRaAb+6YjDElbPPxzAqq0QQHFRphZUIzo4lMMzO6evdATnKoZNUUL59W0EyqlN4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724893500; c=relaxed/simple; bh=xB08nBAPl61OofPOGvwFRENxEZD1qCG61thY+k7r1kw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=gejoCKZaZOcW1sPP+Nrs6s5GjjtypJoXxcC3VvlWI32nKqKTK5JFb+3l+T0qiS5GYHFkw1htbmyUyFX9q+20P7t85YHJZfbwVJdzMRdWsjesGgpscsj7mtxvhJT5zLW4EZfeYx7emZJCtyYObv5nV8dhtYtpj5VpckT6SiNf+3w= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=J3vwm91+; 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="J3vwm91+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6000AC4CEC0; Thu, 29 Aug 2024 01:04:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1724893499; bh=xB08nBAPl61OofPOGvwFRENxEZD1qCG61thY+k7r1kw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=J3vwm91+pfep6ywXjzulH491xDiAOp5OVtzGRsCJMR+hUMxZNRbWW/UnDvtjocpUl ts63Laz/L0JoQiMykPsFJq4FmCMMM/aAgLtzQl9ERbwkpqgToIUCx8bgX74+LU2cdh CN7+rVCEKsHzi4GebiGIHRQzuK8x2nNKBMZhXlHx31+2hZ+S/OJGfj6hWVqX436Wvx zcutbDrczOkayBpA7oVOASTflKfL/BS0dkcatZCzEIeKhlml5rFsun8/4ESbFGCz+O k3/zeVKM0CTPltTsRAoG5kFwHg+R3V17y83KdNYCdZcvXCVXDY232bSkaJc/ABPYE3 1r96VKwjCeidw== 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 25/25] nfs: add FAQ section to Documentation/filesystems/nfs/localio.rst Date: Wed, 28 Aug 2024 21:04:20 -0400 Message-ID: <20240829010424.83693-26-snitzer@kernel.org> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240829010424.83693-1-snitzer@kernel.org> References: <20240829010424.83693-1-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 8cceb3db386a..4b6d63246479 100644 --- a/Documentation/filesystems/nfs/localio.rst +++ b/Documentation/filesystems/nfs/localio.rst @@ -61,6 +61,83 @@ 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. 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 ===