From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=62.210.214.84 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793241981; b=PaQJjnRRQPRbRMermsBtcudO7jBgG1RQ1NOB7ksM8vcLFbs8Ol3/vTFx5pAnCttg5Wed bzSE1NI008xwCXHcJgVl4yLqOw+QSm39+wAGZy7oCbJnh577Z4ye2GHd/XbXqe+w8qlxV p8tVOCclU5125vwtYIicE6375ATnvaNLWhoKdx95PaIlSaf5fKg8mGFifZEtDwUzsfk8k /wiy70LW8JVbX0pL9KWwwBReY/KsBy98MW3wMa47E/GgqTE8YItj7fNNOTBP4MM/8Db1Z XAw1zZly5MVVa8AOrcRP55Y5Qr4p6eIboilqyJr/lrDgv+kD8+ccFJ3gtLnhQQByvNQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793241981; h=DMARC-Filter:Received:DKIM-Signature:Received:Date:From:To:Cc: Subject:Message-ID:References:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; bh=PABQUNtwzA7tp2WIdIkVm8tzuMcr4y+wWPxd8RLkMGk=; b=gjB/TFdpS17xAAzNoF66w2wPZI9hG5qY4XlW3+LDX/rbLxOla6Ww0n1zyoqbCjUxWKZh JUqAle0AOkV/8+7urNRtzDaePCE6h6UexCCOw/vFZVzkZAq5eKQUboMvEVFMW2OE+FBtv 2ETgvByqEn5tMQQY2eMf803xvrHHAD5ccDo/n4nOB5Qiove5OInG9KJ0S2WHG/e4FQaGX TBnTDEsrJ7hfdJtq29F92r9MVAJF7qJ0QBP9OEqNfkk4jpVXgG7rmA/CJ/CT0jdAboT8D p4rHLlr4H9RKokIt971ik8eJgfDB+6/aoKoZXVsn9YPcwagdrrNYKTASZsF7f5mjWnA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=codewreck.org; spf=pass smtp.mailfrom=codewreck.org; dkim=pass header.d=codewreck.org header.i=@codewreck.org header.a=rsa-sha256 header.s=2 header.b=SayRpoU0; arc=none smtp.remote-ip=62.210.214.84 Received: from submarine.notk.org (submarine.notk.org [62.210.214.84]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CBFE1606A31C for ; Thu, 29 Oct 2026 02:46:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org CBFE1606A31C Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=codewreck.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=codewreck.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=codewreck.org header.i=@codewreck.org header.a=rsa-sha256 header.s=2 header.b=SayRpoU0 Received: from gaia.codewreck.org (localhost [127.0.0.1]) by submarine.notk.org (Postfix) with ESMTPS id 99A0B14C2D6; Thu, 29 Oct 2026 03:46:13 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=codewreck.org; s=2; t=1793241976; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=PABQUNtwzA7tp2WIdIkVm8tzuMcr4y+wWPxd8RLkMGk=; b=SayRpoU0s+/TQ1WuZe4o/5liJzEtyY0Ch/PDlpO9NxyVwx7wBoIwb6jSmg1hmjWXSkV4hJ 4JzHeZSHMtuRZqHGVoRJgpaOCo1K3WAM0AmqQUK5SJD0dreuMVeEV1EcMg28060HokvO0l luhnibaYFzKSkxsF/AzWQUu0ZZWpKg9nZUKjRI3xLgdA9D8jdi8mogTt4H8mkQvntdY1Kh aUE8rRpDDwCdwQ2Qo1PSqUY02t9w5+uvBQ7ESivCc/jxPpMnwGZGU1eBL7n15UNt4oLFXd n0hkQJl8mCxEVLo1nZ9UCziAU7jpmF3pXWy0cSg/jdZCHpkulq9Vqj0CX+dGzw== Received: from localhost (gaia.codewreck.org [local]) by gaia.codewreck.org (OpenSMTPD) with ESMTPA id 438811e2; Thu, 29 Oct 2026 02:46:11 +0000 (UTC) Date: Thu, 29 Oct 2026 11:45:56 +0900 From: Dominique Martinet To: Alan Borzeszkowski Cc: ericvh@kernel.org, lucho@ionkov.net, mika.westerberg@linux.intel.com, andreas.noever@gmail.com, YehezkelShB@gmail.com, corbet@lwn.net, linux-usb@vger.kernel.org, v9fs@lists.linux.dev, linux-doc@vger.kernel.org, linux_oss@crudebyte.com Subject: Re: [PATCH 0/3] net/9p: Add 9P transport over USB4STREAM Message-ID: References: <20260924162333.147033-1-alan.borzeszkowski@linux.intel.com> X-Mailing-List: v9fs@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260924162333.147033-1-alan.borzeszkowski@linux.intel.com> Alan Borzeszkowski wrote on Thu, Sep 24, 2026 at 06:23:30PM +0200: > This series adds trans=thunderbolt, a 9P transport over the > Thunderbolt/USB4 DMA tunnels exposed by the tbstream character devices > (USB4STREAM). It's designed for simple host-to-host file sharing over > single Thunderbolt/USB4 cable. > > Today the only practical way to use 9P over a USB4 link is trans=fd > which, due to its design, cannot fully utilize USB4STREAM capabilities. > Thunderbolt transport offers a simpler mount (no fd redirection required), > busy-poll support and substantial throughput increase compared to FD > transport. > > User may mount 9P export with following command: > > mount -t 9p -o trans=thunderbolt,aname= /dev/tbstreamX /mnt > > Thunderbolt transport achieves a median 1.21x more throughput compared > to FD transport under same conditions, and the advantage grows with > concurrency: 1.03-1.09x at 1-2 threads, 1.14-1.27x at 4, and 1.34-2.28x > at 8-16. > > As an example, 4K random reads, 4 worker threads. FD transport achieves > ~53k IOPS, Thunderbolt transport ~66k (+24.7%). 4K random writes follow: > FD ~28k IOPS, Thunderbolt ~33k (+19.4%). Thanks for the patches We've kept adding new transports for 9p lately but maintenance is becoming a burden so let me push back a bit: is the increased performance really worth it over trans=fd ? If this could be used to bringup a system with a root filesystem like it was done for trans=usbg I'd see the point, but otherwise the simpler usage could be addressed with a simple mount.9p helper, and at this point I'd consider usb4stream to be used for perhaps one-shot copy and not care too much about 4k random IOs (so less affected by latency if msize is large enough, and for a one-shot backup it doesn't matter too much if it takes 6 instead of 5 minutes) If you can convince me this is worth it and can take care of the transport for the forseable future I'm not dead set to refuse this, but I can't say I'm convinced right now, especially as I can't even test this (I don't own two computers with working usb-c...) Thanks, -- Dominique Martinet | Asmadeus