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 92AE4175D53 for ; Mon, 10 Mar 2025 12:08:30 +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=1741608510; cv=none; b=lXd8CTJA6Y4RDcHvw3yGAD+hmdIC7fcypan0ktmg6+uIJjLFlmypm3SOfvJz0SJraUnT3U2ZF+CywIq0KCsj72k9INEynClExnvun5MrF9RbttZsH84C9FxtbQOA4//pM19Tcv3st3A9ygHl9nPPafJhSk4SQK+sP9m9uokT02A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741608510; c=relaxed/simple; bh=fgnB41N8BLdf3IrjnLD8FrffgN1GUN9TyDSDjZ71Q1Y=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=Ehn4i4kz6wg+11zM85Tq6ftxuf34+aGwoVKf3Z5YNt+XDAEatYzKwasP/KlV/De5WasQkH7LuaxtRWb3iyEPTlCBsIn+x47ExPDpabqgPqnwrhkShEZ99OJ5t9NHJGDc1f20rmYirkmq+8TXOyT39ULQvrFfVJ72tlGTM0tWz00= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=snPKvdz8; 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="snPKvdz8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6196BC4CEE5; Mon, 10 Mar 2025 12:08:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1741608510; bh=fgnB41N8BLdf3IrjnLD8FrffgN1GUN9TyDSDjZ71Q1Y=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=snPKvdz8AprMztDuvGVmKzsR0GALhEtTYkahpvotDnxadTbFcOSyk1S2rMBPlJNW9 ZOokKmh5e2C8yQFL3IfBx53zGSkKem9b4WLJ1OZ5IPkpRUMIfZKyU4FXvFv9zcr9ZP b7ImUGGM0W9LMLWidr+zYKUIz1UNgo45mbtml4mNt0jA7cnQm0vzd3Ebb+ODW+bKXr D3+KOGUgYiExNEtQkyeaoV49DuXZMZqSbH++nl2WD8j8vr/UNXFuqd1vONcmy5RHVG rxLetVbj2QNZfMuvqjE/H3KLY7kXwiq9+6NoX6WHfYrWzccVj4bTzIRUimuTqcqYeX VWxT27BkP/PdQ== Message-ID: Subject: Re: [RFC PATCH 0/2] NFSD: add a setting to disable splice reads From: Jeff Layton To: cel@kernel.org, Neil Brown , Olga Kornievskaia , Dai Ngo , Tom Talpey Cc: linux-nfs@vger.kernel.org, Trond Myklebust , Chuck Lever Date: Mon, 10 Mar 2025 08:08:28 -0400 In-Reply-To: <20250308201438.2217-1-cel@kernel.org> References: <20250308201438.2217-1-cel@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 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appears, it is difficult to change or remove, in order to > maintain backwards compatibility with user space software. >=20 > This series introduces /sys/kernel/debug/nfsd/ where we can > hopefully place ephemeral and undocumented settings for testing NFSD > features that are to be added or deprecated without the worry of > having to support an administrative API forever without change, > amen. >=20 > As a first consumer of this user-kernel API, the series adds a > simple disable-splice-read setting, which can force all NFS READ > operations to use vfs_iter_read() rather than page splicing to fill > data content for an NFS reply. >=20 > The splice read path is the default on most file systems, so it gets > most of the test experience. The purpose of this new setting is to > enable test runners to force the use of the iov iter path. We are > also interested in comparing the performance of the splice and iter > paths, as a prelude to potentially removing page splicing. This new > setting makes it easy to benchmark either read mode without having > to rebuild the kernel. >=20 > We have an eye on a few other consumers, such as uncached I/O and > increasing the maximum r/wsize, for which /sys/kernel/debug/nfsd > might be suitable while their performance impact is studied before > a concrete administrative interface is agreed upon. >=20 > Opinions and code review are welcome, as always. >=20 > Chuck Lever (2): > NFSD: Add /sys/kernel/debug/nfsd > NFSD: Add experimental setting to disable the use of splice read >=20 > fs/nfsd/Makefile | 1 + > fs/nfsd/debugfs.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++ > fs/nfsd/nfsctl.c | 4 ++++ > fs/nfsd/nfsd.h | 10 ++++++++++ > fs/nfsd/vfs.c | 4 ++++ > 5 files changed, 66 insertions(+) > create mode 100644 fs/nfsd/debugfs.c >=20 Looks good to me: Reviewed-by: Jeff Layton