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 D89FE2DCF56 for ; Tue, 15 Jul 2025 11:28:45 +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=1752578925; cv=none; b=QDfVwlIsNhAN21GWHzWoPHDI99NtDetAh+z9Rq1l4lewVS+cb/8hanGAY1fcTwRqdQLXBseEl9O3Y+mzNaHYAxMOtWogWVCzBgyoCvX7r37hsUkF5h4OmssC96aQhwZan9y36dNoFZVj0jzn378JSW+EdyubAwC7YmolB5Zhdvo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752578925; c=relaxed/simple; bh=2pIZvCCs0rLA67/s4z9oCBFXjuaSQg/cNRqmPhQU284=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=l0vwWtv3Fe8tYVRLth5arqTo2uLDMt6S9c1XEJjagXUphcR6/yzSB4BLWBYDxgm5Jo2Z70Z+3iqrfm+UOmeu3piO16ecezXpcPFuj47EyrUNAOhfV+VsMld2Rvj2Zk6/7bam9ft2zaXNBVS77mA7VaafC3jV0cF3ysVUX3j4264= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=EY6ScinZ; 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="EY6ScinZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DEDD0C4CEF6; Tue, 15 Jul 2025 11:28:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1752578925; bh=2pIZvCCs0rLA67/s4z9oCBFXjuaSQg/cNRqmPhQU284=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=EY6ScinZjZvScolsTxcJq7VISABnCo9hEFV9VqedPFKtGD7CAIF3PHNCcqVr7dtt/ sbypbAXez3hi/lsnwBuf24NWKfGSz+qJIHSfFZiIKKHKz4qTxRIdivbUmFGEiEZwJm PRp1jjYOmx2reKH/K5HVHbH0MWmfOTxsakIqGZ6pL3AT8dNHU7jGHGcqQk1STFfPRu yxxTScwEDnuAuyQAoYJAAF3G4XJPjPNvqF3aDnOt/UIEpApwPdhHB15MjBiM+ZqcvI gDG8QIcgwSaBz3u+GWntCmD2/mmEOSnslx1UKffOxIrAn2WltwTgZ2McjcYEs79T32 vejVFGj+s0TNA== Message-ID: <1c3196b0d57c94f29f7a29402ae6e66ae44c9d02.camel@kernel.org> Subject: Re: [PATCH v3 0/5] NFSD: add "NFSD DIRECT" and "NFSD DONTCACHE" IO modes From: Jeff Layton To: Daire Byrne , Mike Snitzer Cc: Chuck Lever , linux-nfs@vger.kernel.org Date: Tue, 15 Jul 2025 07:28:43 -0400 In-Reply-To: References: <20250714224216.14329-1-snitzer@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 0OX6MYPtv76hka8lW4mnRmZqqx3UtfHX/hF/zH24Gj7A6sYKYLCU3YrI2Ogiu7/ksKcl7goQjpvtV YrOOI5VGLHge0awt7bhMCTM9KAfPc+xL/ZxAMVWd3NCk5SamL2cE99UWgtvNOIYU8m6EjTLhsj8sn VluJH0/RcxEeFbnSaswVChNSGa7mXJrTR22lRL6ZPjdMgS2Km90haWPRc8Wolcz07Y2se0xpGVLEQ cDEsvv5IMmeMe1/qLZ6NaVkNuL3WOXvxaVT9USW1+/SGipO2IpKJjeDZfehlB/kpfF24+RrK+seQf CBYyUE8QJpvTZyfUHNYldXlrjO6n5MdOempLqWpfOmcGkwnyNRBR46g/jf8KnPRwXs509yAqDB6sE LZH+yWr9LQZEwARAQABtCVKZWZmIExheXRvbiA8amxheXRvbkBwb29jaGllcmVkcy5uZXQ+iQI7BB MBAgAlAhsDBgsJCAcDAgYVCAIJCgsEFgIDAQIeAQIXgAUCTpXWPAIZAQAKCRAADmhBGVaCFc65D/4 gBLNMHopQYgG/9RIM3kgFCCQV0pLv0hcg1cjr+bPI5f1PzJoOVi9s0wBDHwp8+vtHgYhM54yt43uI 7Htij0RHFL5eFqoVT4TSfAg2qlvNemJEOY0e4daljjmZM7UtmpGs9NN0r9r50W82eb5Kw5bc/r0km R/arUS2st+ecRsCnwAOj6HiURwIgfDMHGPtSkoPpu3DDp/cjcYUg3HaOJuTjtGHFH963B+f+hyQ2B rQZBBE76ErgTDJ2Db9Ey0kw7VEZ4I2nnVUY9B5dE2pJFVO5HJBMp30fUGKvwaKqYCU2iAKxdmJXRI ONb7dSde8LqZahuunPDMZyMA5+mkQl7kpIpR6kVDIiqmxzRuPeiMP7O2FCUlS2DnJnRVrHmCljLkZ Wf7ZUA22wJpepBligemtSRSbqCyZ3B48zJ8g5B8xLEntPo/NknSJaYRvfEQqGxgk5kkNWMIMDkfQO lDSXZvoxqU9wFH/9jTv1/6p8dHeGM0BsbBLMqQaqnWiVt5mG92E1zkOW69LnoozE6Le+12DsNW7Rj iR5K+27MObjXEYIW7FIvNN/TQ6U1EOsdxwB8o//Yfc3p2QqPr5uS93SDDan5ehH59BnHpguTc27Xi QQZ9EGiieCUx6Zh2ze3X2UW9YNzE15uKwkkuEIj60NvQRmEDfweYfOfPVOueC+iFifbQgSmVmZiBM YXl0b24gPGpsYXl0b25AcmVkaGF0LmNvbT6JAjgEEwECACIFAk6V0q0CGwMGCwkIBwMCBhUIAgkKC wQWAgMBAh4BAheAAAoJEAAOaEEZVoIViKUQALpvsacTMWWOd7SlPFzIYy2/fjvKlfB/Xs4YdNcf9q LqF+lk2RBUHdR/dGwZpvw/OLmnZ8TryDo2zXVJNWEEUFNc7wQpl3i78r6UU/GUY/RQmOgPhs3epQC 3PMJj4xFx+VuVcf/MXgDDdBUHaCTT793hyBeDbQuciARDJAW24Q1RCmjcwWIV/pgrlFa4lAXsmhoa c8UPc82Ijrs6ivlTweFf16VBc4nSLX5FB3ls7S5noRhm5/Zsd4PGPgIHgCZcPgkAnU1S/A/rSqf3F LpU+CbVBDvlVAnOq9gfNF+QiTlOHdZVIe4gEYAU3CUjbleywQqV02BKxPVM0C5/oVjMVx3bri75n1 TkBYGmqAXy9usCkHIsG5CBHmphv9MHmqMZQVsxvCzfnI5IO1+7MoloeeW/lxuyd0pU88dZsV/riHw 87i2GJUJtVlMl5IGBNFpqoNUoqmvRfEMeXhy/kUX4Xc03I1coZIgmwLmCSXwx9MaCPFzV/dOOrju2 xjO+2sYyB5BNtxRqUEyXglpujFZqJxxau7E0eXoYgoY9gtFGsspzFkVNntamVXEWVVgzJJr/EWW0y +jNd54MfPRqH+eCGuqlnNLktSAVz1MvVRY1dxUltSlDZT7P2bUoMorIPu8p7ZCg9dyX1+9T6Muc5d Hxf/BBP/ir+3e8JTFQBFOiLNdFtB9KZWZmIExheXRvbiA8amxheXRvbkBzYW1iYS5vcmc+iQI4BBM BAgAiBQJOldK9AhsDBgsJCAcDAgYVCAIJCgsEFgIDAQIeAQIXgAAKCRAADmhBGVaCFWgWD/0ZRi4h N9FK2BdQs9RwNnFZUr7JidAWfCrs37XrA/56olQl3ojn0fQtrP4DbTmCuh0SfMijB24psy1GnkPep naQ6VRf7Dxg/Y8muZELSOtsv2CKt3/02J1BBitrkkqmHyni5fLLYYg6fub0T/8Kwo1qGPdu1hx2BQ RERYtQ/S5d/T0cACdlzi6w8rs5f09hU9Tu4qV1JLKmBTgUWKN969HPRkxiojLQziHVyM/weR5Reu6 FZVNuVBGqBD+sfk/c98VJHjsQhYJijcsmgMb1NohAzwrBKcSGKOWJToGEO/1RkIN8tqGnYNp2G+aR 685D0chgTl1WzPRM6mFG1+n2b2RR95DxumKVpwBwdLPoCkI24JkeDJ7lXSe3uFWISstFGt0HL8Eew P8RuGC8s5h7Ct91HMNQTbjgA+Vi1foWUVXpEintAKgoywaIDlJfTZIl6Ew8ETN/7DLy8bXYgq0Xzh aKg3CnOUuGQV5/nl4OAX/3jocT5Cz/OtAiNYj5mLPeL5z2ZszjoCAH6caqsF2oLyAnLqRgDgR+wTQ T6gMhr2IRsl+cp8gPHBwQ4uZMb+X00c/Amm9VfviT+BI7B66cnC7Zv6Gvmtu2rEjWDGWPqUgccB7h dMKnKDthkA227/82tYoFiFMb/NwtgGrn5n2vwJyKN6SEoygGrNt0SI84y6hEVbQlSmVmZiBMYXl0b 24gPGpsYXl0b25AcHJpbWFyeWRhdGEuY29tPokCOQQTAQIAIwUCU4xmKQIbAwcLCQgHAwIBBhUIAg kKCwQWAgMBAh4BAheAAAoJEAAOaEEZVoIV1H0P/j4OUTwFd7BBbpoSp695qb6HqCzWMuExsp8nZjr uymMaeZbGr3OWMNEXRI1FWNHMtcMHWLP/RaDqCJil28proO+PQ/yPhsr2QqJcW4nr91tBrv/MqItu AXLYlsgXqp4BxLP67bzRJ1Bd2x0bWXurpEXY//VBOLnODqThGEcL7jouwjmnRh9FTKZfBDpFRaEfD FOXIfAkMKBa/c9TQwRpx2DPsl3eFWVCNuNGKeGsirLqCxUg5kWTxEorROppz9oU4HPicL6rRH22Ce 6nOAON2vHvhkUuO3GbffhrcsPD4DaYup4ic+DxWm+DaSSRJ+e1yJvwi6NmQ9P9UAuLG93S2MdNNbo sZ9P8k2mTOVKMc+GooI9Ve/vH8unwitwo7ORMVXhJeU6Q0X7zf3SjwDq2lBhn1DSuTsn2DbsNTiDv qrAaCvbsTsw+SZRwF85eG67eAwouYk+dnKmp1q57LDKMyzysij2oDKbcBlwB/TeX16p8+LxECv51a sjS9TInnipssssUDrHIvoTTXWcz7Y5wIngxDFwT8rPY3EggzLGfK5Zx2Q5S/N0FfmADmKknG/D8qG IcJE574D956tiUDKN4I+/g125ORR1v7bP+OIaayAvq17RP+qcAqkxc0x8iCYVCYDouDyNvWPGRhbL UO7mlBpjW9jK9e2fvZY9iw3QzIPGKtClKZWZmIExheXRvbiA8amVmZi5sYXl0b25AcHJpbWFyeWRh dGEuY29tPokCOQQTAQIAIwUCU4xmUAIbAwcLCQgHAwIBBhUIAgkKCwQWAgMBAh4BAheAAAoJEAAOa EEZVoIVzJoQALFCS6n/FHQS+hIzHIb56JbokhK0AFqoLVzLKzrnaeXhE5isWcVg0eoV2oTScIwUSU apy94if69tnUo4Q7YNt8/6yFM6hwZAxFjOXR0ciGE3Q+Z1zi49Ox51yjGMQGxlakV9ep4sV/d5a50 M+LFTmYSAFp6HY23JN9PkjVJC4PUv5DYRbOZ6Y1+TfXKBAewMVqtwT1Y+LPlfmI8dbbbuUX/kKZ5d dhV2736fgyfpslvJKYl0YifUOVy4D1G/oSycyHkJG78OvX4JKcf2kKzVvg7/Rnv+AueCfFQ6nGwPn 0P91I7TEOC4XfZ6a1K3uTp4fPPs1Wn75X7K8lzJP/p8lme40uqwAyBjk+IA5VGd+CVRiyJTpGZwA0 jwSYLyXboX+Dqm9pSYzmC9+/AE7lIgpWj+3iNisp1SWtHc4pdtQ5EU2SEz8yKvDbD0lNDbv4ljI7e flPsvN6vOrxz24mCliEco5DwhpaaSnzWnbAPXhQDWb/lUgs/JNk8dtwmvWnqCwRqElMLVisAbJmC0 BhZ/Ab4sph3EaiZfdXKhiQqSGdK4La3OTJOJYZphPdGgnkvDV9Pl1QZ0ijXQrVIy3zd6VCNaKYq7B AKidn5g/2Q8oio9Tf4XfdZ9dtwcB+bwDJFgvvDYaZ5bI3ln4V3EyW5i2NfXazz/GA/I/ZtbsigCFc 8ftCBKZWZmIExheXRvbiA8amxheXRvbkBrZXJuZWwub3JnPokCOAQTAQIAIgUCWe8u6AIbAwYLCQg HAwIGFQgCCQoLBBYCAwECHgECF4AACgkQAA5oQRlWghUuCg/+Lb/xGxZD2Q1oJVAE37uW308UpVSD 2tAMJUvFTdDbfe3zKlPDTuVsyNsALBGclPLagJ5ZTP+Vp2irAN9uwBuacBOTtmOdz4ZN2tdvNgozz uxp4CHBDVzAslUi2idy+xpsp47DWPxYFIRP3M8QG/aNW052LaPc0cedYxp8+9eiVUNpxF4SiU4i9J DfX/sn9XcfoVZIxMpCRE750zvJvcCUz9HojsrMQ1NFc7MFT1z3MOW2/RlzPcog7xvR5ENPH19ojRD CHqumUHRry+RF0lH00clzX/W8OrQJZtoBPXv9ahka/Vp7kEulcBJr1cH5Wz/WprhsIM7U9pse1f1g Yy9YbXtWctUz8uvDR7shsQxAhX3qO7DilMtuGo1v97I/Kx4gXQ52syh/w6EBny71CZrOgD6kJwPVV AaM1LRC28muq91WCFhs/nzHozpbzcheyGtMUI2Ao4K6mnY+3zIuXPygZMFr9KXE6fF7HzKxKuZMJO aEZCiDOq0anx6FmOzs5E6Jqdpo/mtI8beK+BE7Va6ni7YrQlnT0i3vaTVMTiCThbqsB20VrbMjlhp f8lfK1XVNbRq/R7GZ9zHESlsa35ha60yd/j3pu5hT2xyy8krV8vGhHvnJ1XRMJBAB/UYb6FyC7S+m QZIQXVeAA+smfTT0tDrisj1U5x6ZB9b3nBg65kc= Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 (3.56.2-1.fc42) Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Understood. We're not looking to abandon you guys. I think bog-standard buffered I/O will be the default option for the forseeable future. We are pretty keen to add other I/O modes as an _option_, however because they do help other important workloads. The hard part is how we make this tunable without shooting our future selves in our collective feet. That's the main reason this is all being done in debugfs for the moment, since that carries no ABI guarantees. -- Jeff On Tue, 2025-07-15 at 10:24 +0100, Daire Byrne wrote: > Just a quick note to say that we are one of the examples (batch render > farm) where we rely on the NFSD pagecache a lot. >=20 > We have read heavy workloads where many clients share much of the same > input data (e.g. rendering sequential frames). >=20 > In fact, our 2 x 100gbit servers have 3TB of RAM and serve 70% of all > reads from nfsd pagecache. It is not uncommon to max out the 200gbit > network in this way even with spinning rust storage. >=20 > Anyway, as you were. >=20 > Daire >=20 > On Mon, 14 Jul 2025 at 23:42, Mike Snitzer wrote: > >=20 > > Hi, > >=20 > > Summary (by Jeff Layton [0]): > > "The basic problem is that the pagecache is pretty useless for > > satisfying READs from nfsd. Most NFS workloads don't involve I/O to > > the same files from multiple clients. The client ends up having most > > of the data in its cache already and only very rarely do we need to > > revisit the data on the server. > >=20 > > At the same time, it's really easy to overwhelm the storage with > > pagecache writeback with modern memory sizes. Having nfsd bypass the > > pagecache altogether is potentially a huge performance win, if it can > > be made to work safely." > >=20 > > The performance win associated with using NFSD DIRECT was previously > > summarized here: > > https://lore.kernel.org/linux-nfs/aEslwqa9iMeZjjlV@kernel.org/ > > This picture offers a nice summary of performance gains: > > https://original.art/NFSD_direct_vs_buffered_IO.jpg > >=20 > > This v3 series was developed ontop of Chuck's nfsd_testing which has 2 > > patches that saw fh_getattr() moved, etc (v2 of this series included > > those patches but since they got review during v2 and Chuck already > > has them staged in nfsd-testing I didn't think it made sense to keep > > them included in this v3). > >=20 > > Changes since v2 include: > > - explored suggestion to use string based interface (e.g. "direct" > > instead of 3) but debugfs seems to only supports numeric values. > > - shifted numeric values for debugfs interface from 0-2 to 1-3 and > > made 0 UNSPECIFIED (which is the default) > > - if user specifies io_cache_read or io_cache_write mode other than 1, > > 2 or 3 (via debugfs) they will get an error message > > - pass a data structure to nfsd_analyze_read_dio rather than so many > > in/out params > > - improved comments as requested (e.g. "Must remove first > > start_extra_page from rqstp->rq_bvec" was reworked) > > - use memmove instead of opencoded shift in > > nfsd_complete_misaligned_read_dio > > - dropped the still very important "lib/iov_iter: remove piecewise > > bvec length checking in iov_iter_aligned_bvec" patch because it > > needs to be handled separately. > > - various other changes to improve code > >=20 > > Thanks, > > Mike > >=20 > > [0]: https://lore.kernel.org/linux-nfs/b1accdad470f19614f9d3865bb3a4c69= 958e5800.camel@kernel.org/ > >=20 > > Mike Snitzer (5): > > NFSD: filecache: add STATX_DIOALIGN and STATX_DIO_READ_ALIGN support > > NFSD: pass nfsd_file to nfsd_iter_read() > > NFSD: add io_cache_read controls to debugfs interface > > NFSD: add io_cache_write controls to debugfs interface > > NFSD: issue READs using O_DIRECT even if IO is misaligned > >=20 > > fs/nfsd/debugfs.c | 102 +++++++++++++++++++ > > fs/nfsd/filecache.c | 32 ++++++ > > fs/nfsd/filecache.h | 4 + > > fs/nfsd/nfs4xdr.c | 8 +- > > fs/nfsd/nfsd.h | 10 ++ > > fs/nfsd/nfsfh.c | 4 + > > fs/nfsd/trace.h | 37 +++++++ > > fs/nfsd/vfs.c | 197 ++++++++++++++++++++++++++++++++++--- > > fs/nfsd/vfs.h | 2 +- > > include/linux/sunrpc/svc.h | 5 +- > > 10 files changed, 383 insertions(+), 18 deletions(-) > >=20 > > -- > > 2.44.0 > >=20 > >=20 --=20 Jeff Layton