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 721BE21E0A8; Mon, 16 Jun 2025 16:10:40 +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=1750090240; cv=none; b=k1HbeQ1lHCfA6k6Rs7tfJcqnASNHJ7ecqBGU1LKrQvLktRFamrBy53zUls19xinQAoA/oHElfswJatsDTwE7wtTB4Hk07MANGBTUR+JawICv3O4+VQcPxnd7rH+8tSBKKybs/RJknnwvH25eM7zl9g/Prxlin17UXH2bIyLiKEc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750090240; c=relaxed/simple; bh=msta/VbRK4gFFOO94yUWl0CZPF3iEp7ftLxtL7Ax3sY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=O5+o+ccHdrbZREkuBjThnceOlGndeavsCN4NJYNlserEXq4Lqit+/iUoZ+k7kluVJJtiC7/NTdWleHKwd2vgdtIU8gmulj4CJ4uRqV5j9jZ9POS5PaG/oq309WekIiR4Jsc3/YpmQCoQ6AoNiSzgRfTtFilsmZYgQQqIy15/TcY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XIbNymSw; 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="XIbNymSw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A8B36C4CEEA; Mon, 16 Jun 2025 16:10:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1750090239; bh=msta/VbRK4gFFOO94yUWl0CZPF3iEp7ftLxtL7Ax3sY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=XIbNymSwIC0PE9FjaRW1bOtcNfLgHmkCYGTYGLFUXf4LGIeX3Is1J34xu+QOv3/nb kMJ+KsuzfTpn/QpCaRh2pnT3E7adiiRmwCl5VzqPtvllbkZ2emMWwuEte4V/S11EJB 3B9sVrF4fNaJiMAAF3AKsntwsWQ2TLn//fqnGrkZCaPu3oatQ0+uAFC/nxky3h/Wuo oCmuWZiFAukkXHvhfLTc7j6XK8BmnSQ1VQPG6S88NQpQlQG7BjYX/LEnFnSopincwP frqd9Zz6jHiu7G/LuzlVl3U5yTA/eYq/SQkKndsGOB4GJQlqSMvsnMUs15JoHkPY2f Ud/R0Is17oOjw== Date: Mon, 16 Jun 2025 12:10:38 -0400 From: Mike Snitzer To: Chuck Lever Cc: Jeff Layton , linux-nfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, Jens Axboe Subject: Re: [PATCH 1/6] NFSD: add the ability to enable use of RWF_DONTCACHE for all IO Message-ID: References: <20250610205737.63343-1-snitzer@kernel.org> <20250610205737.63343-2-snitzer@kernel.org> <4b858fb1-25f6-457f-8908-67339e20318e@oracle.com> <5dc44ffd-9055-452c-87c6-2572e5a97299@oracle.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5dc44ffd-9055-452c-87c6-2572e5a97299@oracle.com> On Mon, Jun 16, 2025 at 09:32:16AM -0400, Chuck Lever wrote: > On 6/12/25 12:00 PM, Mike Snitzer wrote: > > On Thu, Jun 12, 2025 at 09:21:35AM -0400, Chuck Lever wrote: > >> On 6/11/25 3:18 PM, Mike Snitzer wrote: > >>> On Wed, Jun 11, 2025 at 10:31:20AM -0400, Chuck Lever wrote: > >>>> On 6/10/25 4:57 PM, Mike Snitzer wrote: > >>>>> Add 'enable-dontcache' to NFSD's debugfs interface so that: Any data > >>>>> read or written by NFSD will either not be cached (thanks to O_DIRECT) > >>>>> or will be removed from the page cache upon completion (DONTCACHE). > >>>> > >>>> I thought we were going to do two switches: One for reads and one for > >>>> writes? I could be misremembering. > >>> > >>> We did discuss the possibility of doing that. Still can-do if that's > >>> what you'd prefer. > >> > >> For our experimental interface, I think having read and write enablement > >> as separate settings is wise, so please do that. > >> > >> One quibble, though: The name "enable_dontcache" might be directly > >> meaningful to you, but I think others might find "enable_dont" to be > >> oxymoronic. And, it ties the setting to a specific kernel technology: > >> RWF_DONTCACHE. > >> > >> So: Can we call these settings "io_cache_read" and "io_cache_write" ? > >> > >> They could each carry multiple settings: > >> > >> 0: Use page cache > >> 1: Use RWF_DONTCACHE > >> 2: Use O_DIRECT > >> > >> You can choose to implement any or all of the above three mechanisms. > > > > I like it, will do for v2. But will have O_DIRECT=1 and RWF_DONTCACHE=2. > > For io_cache_read, either settings 1 and 2 need to set > disable_splice_read, or the io_cache_read setting has to be considered > by nfsd_read_splice_ok() when deciding to use nfsd_iter_read() or > splice read. Yes, I understand. > However, it would be slightly nicer if we could decide whether splice > read can be removed /before/ this series is merged. Can you get NFSD > tested with IOR with disable_splice_read both enabled and disabled (no > direct I/O)? Then we can compare the results to ensure that there is no > negative performance impact for removing the splice read code. I can ask if we have a small window of opportunity to get this tested, will let you know if so.