From mboxrd@z Thu Jan 1 00:00:00 1970 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 9A63A14D2B5; Wed, 21 Aug 2024 19:03:09 +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=1724266989; cv=none; b=dY91vhpJpc17oMNvSLDaSJ0F+ScVhOn6pkVjgz2gGz4GooRYYfPgSAIxQ6mAhN7jao8vPYK22LRza8wmmMJdnVYhpXHiI6NX19XlHjEXOesAYZCm68ASEnRFTxGjiq0+5k46d5kEj23hBply0E14aFvM1EaV5CDS0HQkWRtyM+Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724266989; c=relaxed/simple; bh=aVndDEUZQBS3oS1ccDgfyxAB006j9n8NaXzpjCXEQEw=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=X0rqiH1dazRPSQrNg+83qwSiWJE3Sz6L+lK+bZ0n/26nwHY2SZUvy0XqVo0z5kusNBlFI+xP8dzx++3sJ/Zqc9YuNCI1jmeN+iPlXuznh/QSFyutnhkCFwLVZnS8d1Nc1dT7XtYNj1clytUIx7PnAozKv6klybbHxPE9bpTV8u8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=B0uyQJMx; 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="B0uyQJMx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7945BC32781; Wed, 21 Aug 2024 19:03:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1724266989; bh=aVndDEUZQBS3oS1ccDgfyxAB006j9n8NaXzpjCXEQEw=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=B0uyQJMx8ni15ShOIXWZmjiRE4rLibUV34QSvaT8mxAw3TOHqCYeJLjFeIrKE94bN B8QuzAUboVESwSs82LVSB4++vGZxO5uzW+twZTe1afpLC+9gdcC38EySwpjveVifj2 hOD3NOyRk+D5cgf8IbY8Kjp4GoKrHHrMW15sE2gMYy2uqnoPXfQD4G6KHOo/eGrLyL kb0B3FiR/PPVDCe//OpsgoqUWBDVCAwenNCwkJTZoR9JNr84OzJqlYExFum0s4A9ER J00IhKBWp2fbhW8+0i8x5uBOvw5qTMfeXFbvBXTbNVfMe8FTxJberf38GUWJGb/EGc PlTPm0DMTvy8A== Message-ID: <115f7c93d81d080ce6aac64eaa4e8616a5fe0cdd.camel@kernel.org> Subject: Re: [PATCH v12 24/24] nfs: add FAQ section to Documentation/filesystems/nfs/localio.rst From: Jeff Layton To: Mike Snitzer , linux-nfs@vger.kernel.org Cc: Chuck Lever , Anna Schumaker , Trond Myklebust , NeilBrown , linux-fsdevel@vger.kernel.org Date: Wed, 21 Aug 2024 15:03:07 -0400 In-Reply-To: <20240819181750.70570-25-snitzer@kernel.org> References: <20240819181750.70570-1-snitzer@kernel.org> <20240819181750.70570-25-snitzer@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV 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Mon, 2024-08-19 at 14:17 -0400, Mike Snitzer wrote: > From: Trond Myklebust >=20 > Add a FAQ section to give answers to questions that have been raised > during review of the localio feature. >=20 > Signed-off-by: Trond Myklebust > Co-developed-by: Mike Snitzer > Signed-off-by: Mike Snitzer > --- > =C2=A0Documentation/filesystems/nfs/localio.rst | 77 ++++++++++++++++++++= +++ > =C2=A01 file changed, 77 insertions(+) >=20 > diff --git a/Documentation/filesystems/nfs/localio.rst b/Documentation/fi= lesystems/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, > =C2=A0- Without LOCALIO: > =C2=A0=C2=A0 read: IOPS=3D12.0k, BW=3D1495MiB/s (1568MB/s)(29.2GiB/20015m= sec) > =C2=A0 > +FAQ > +=3D=3D=3D > + > +1. What are the use cases for LOCALIO? > + > +=C2=A0=C2=A0 a. Workloads where the NFS client and server are on the sam= e host > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 realize improved IO performance. In parti= cular, it is common when > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 running containerised workloads for jobs = to find themselves > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 running on the same host as the knfsd ser= ver being used for > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 storage. > + > +2. What are the requirements for LOCALIO? > + > +=C2=A0=C2=A0 a. Bypass use of the network RPC protocol as much as possib= le. This > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 includes bypassing XDR and RPC for open, = read, write and commit > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 operations. > +=C2=A0=C2=A0 b. Allow client and server to autonomously discover if they= are > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 running local to each other without makin= g any assumptions about > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 the local network topology. > +=C2=A0=C2=A0 c. Support the use of containers by being compatible with r= elevant > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 namespaces (e.g. network, user, mount). > +=C2=A0=C2=A0 d. Support all versions of NFS. NFSv3 is of particular impo= rtance > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 because it has wide enterprise usage and = pNFS flexfiles makes use > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 of it for the data path. > + > +3. Why doesn=E2=80=99t LOCALIO just compare IP addresses or hostnames wh= en > +=C2=A0=C2=A0 deciding if the NFS client and server are co-located on the= same > +=C2=A0=C2=A0 host? > + > +=C2=A0=C2=A0 Since one of the main use cases is containerised workloads,= we cannot > +=C2=A0=C2=A0 assume that IP addresses will be shared between the client = and > +=C2=A0=C2=A0 server. This sets up a requirement for a handshake protocol= that > +=C2=A0=C2=A0 needs to go over the same connection as the NFS traffic in = order to > +=C2=A0=C2=A0 identify that the client and the server really are running = on the > +=C2=A0=C2=A0 same host. The handshake uses a secret that is sent over th= e wire, > +=C2=A0=C2=A0 and can be verified by both parties by comparing with a val= ue stored > +=C2=A0=C2=A0 in shared kernel memory if they are truly co-located. > + > +4. Does LOCALIO improve pNFS flexfiles? > + > +=C2=A0=C2=A0 Yes, LOCALIO complements pNFS flexfiles by allowing it to t= ake > +=C2=A0=C2=A0 advantage of NFS client and server locality.=C2=A0 Policy t= hat initiates > +=C2=A0=C2=A0 client IO as closely to the server where the data is stored= naturally > +=C2=A0=C2=A0 benefits from the data path optimization LOCALIO provides. > + > +5. Why not develop a new pNFS layout to enable LOCALIO? > + > +=C2=A0=C2=A0 A new pNFS layout could be developed, but doing so would pu= t the > +=C2=A0=C2=A0 onus on the server to somehow discover that the client is c= o-located > +=C2=A0=C2=A0 when deciding to hand out the layout. > +=C2=A0=C2=A0 There is value in a simpler approach (as provided by LOCALI= O) that > +=C2=A0=C2=A0 allows the NFS client to negotiate and leverage locality wi= thout > +=C2=A0=C2=A0 requiring more elaborate modeling and discovery of such loc= ality in a > +=C2=A0=C2=A0 more centralized manner. > + > +6. Why is having the client perform a server-side file OPEN, without > +=C2=A0=C2=A0 using RPC, beneficial?=C2=A0 Is the benefit pNFS specific? > + > +=C2=A0=C2=A0 Avoiding the use of XDR and RPC for file opens is beneficia= l to > +=C2=A0=C2=A0 performance regardless of whether pNFS is used. However add= ing a > +=C2=A0=C2=A0 requirement to go over the wire to do an open and/or close = ends up > +=C2=A0=C2=A0 negating any benefit of avoiding the wire for doing the I/O= itself > +=C2=A0=C2=A0 when we=E2=80=99re dealing with small files. There is no be= nefit to replacing > +=C2=A0=C2=A0 the READ or WRITE with a new open and/or close operation th= at still > +=C2=A0=C2=A0 needs to go over the wire. > + > +7. Why is LOCALIO only supported with UNIX Authentication (AUTH_UNIX)? > + > +=C2=A0=C2=A0 Strong authentication is usually tied to the connection its= elf. It > +=C2=A0=C2=A0 works by establishing a context that is cached by the serve= r, and > +=C2=A0=C2=A0 that acts as the key for discovering the authorisation toke= n, which > +=C2=A0=C2=A0 can then be passed to rpc.mountd to complete the authentica= tion > +=C2=A0=C2=A0 process. On the other hand, in the case of AUTH_UNIX, the c= redential > +=C2=A0=C2=A0 that was passed over the wire is used directly as the key i= n the > +=C2=A0=C2=A0 upcall to rpc.mountd. This simplifies the authentication pr= ocess, and > +=C2=A0=C2=A0 so makes AUTH_UNIX easier to support. > + > =C2=A0RPC > =C2=A0=3D=3D=3D > =C2=A0 I'd just squash this into patch #19. --=20 Jeff Layton