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 985AA250BEC for ; Mon, 14 Jul 2025 14:08:49 +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=1752502129; cv=none; b=hWk0Qn7skc7fNXKvNk5b0FVOOXrqELaIKJp6G4im+QiyvVBMOZOw6ArM7cLv4RS2g7IwaRRpQJVl4xlXRhVhmvoCxkSakeA64nsV2t3d7zq5KMQ3AXtrpmCThIqxS3jYX9hZOQP0aHl1pp/S46P8gWqh8K8FALWroJKzA+yMUIo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752502129; c=relaxed/simple; bh=WhkJJLa67xe+oOtYbF79AEllvACuw+AI1zXnmAswAnY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Y4stmH1PP4/kSqCp7suq/Q0iTRv3Fm/qMwbH3r56QZoL5MZ4GD7UInVxFdl2cx1sAocFjPm5R+Bl5BgHRNStIDnAVay0g3c7OxOClwlorgwr93jRBfLMfQozF+dVKGcaWN5DtS1jBzoolk4x3SR2AClllfI/NSweTQDrt8zv/EI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=CkVD7L1n; 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="CkVD7L1n" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DF0E9C4CEF0; Mon, 14 Jul 2025 14:08:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1752502129; bh=WhkJJLa67xe+oOtYbF79AEllvACuw+AI1zXnmAswAnY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=CkVD7L1nKxOiKNt1dspvLKbfRwbbZ0bfHpAl9pbkxBdP1551AZVTxbSdRHMo4oF6+ pqvag72DsWbVkr0XqIPEI40ZlFXlAzuhOhxDzPN3zq8tzXRvyPAVK6ttc7UQg/iaNA BzP8bkS6lLPdNbjd4gurynZI7zPHkMq+h5GnAe6m6fOucBRcQUTg8GXRg6jM6nTdyy w6MqaFtdKOvGmqVWFyqhoJmlZYjV0ky0ZsZUKgf6QqrTeQ2okpm41JCSZJ+eoBI9BA O0T4IPEfdi6mTZyT5XrWR9JbyNoe44A4dcQXaiCBEqQjvOlVKqQq3QHFPQe7qFVlaY SrWJYW8hwubOA== Date: Mon, 14 Jul 2025 10:08:46 -0400 From: Mike Snitzer To: Jeff Layton Cc: NeilBrown , Anna Schumaker , Trond Myklebust , Chuck Lever , linux-nfs@vger.kernel.org Subject: Re: [for-6.16-final PATCH 9/9] nfs/localio: add localio_async_probe modparm Message-ID: References: <20250714031359.10192-1-snitzer@kernel.org> <20250714031359.10192-10-snitzer@kernel.org> <175246700631.2234665.18042187680516755344@noble.neil.brown.name> <579139f6eaaf3f807991e041f509db14d2ffc721.camel@kernel.org> Precedence: bulk X-Mailing-List: linux-nfs@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: <579139f6eaaf3f807991e041f509db14d2ffc721.camel@kernel.org> On Mon, Jul 14, 2025 at 08:28:22AM -0400, Jeff Layton wrote: > On Mon, 2025-07-14 at 14:23 +1000, NeilBrown wrote: > > On Mon, 14 Jul 2025, Mike Snitzer wrote: > > > From: Mike Snitzer > > > > > > This knob influences the LOCALIO handshake so that it happens > > > synchronously upon NFS client creation.. which reduces the window of > > > opportunity for a bunch of IO to flood page cache and send out over to > > > NFSD before LOCALIO handshake negotiates that the client and server > > > are local. The knob is: > > > echo N > /sys/module/nfs/parameters/localio_async_probe > > > > I understand why you are adding this but .... yuck. Tuning knobs are > > best avoided. > > > > Maybe we could still do the probe async, but in mount wait for 200ms, > > or for the probe to get a reply. That should make everyone happy. > > > > NeilBrown > > > > Agreed. I'd prefer to not need a tuning knob for this. Doing a short > wait in the mount for localio negotiation would be a lot more > reasonable. OK. > That said, why is the LOCALIO negotiation taking so long? Shouldn't > that be basically instantaneous during the mount? Do we really have > applications that are hammering reads and writes just after the mount > returns but before the localio negotiation completes? Yes, buffered IO in particular brings the hammer via a storm of page cache IO that takes a while to be complete before LOCALIO ever gets an opportunity to service NFS client IO. Mike