From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.9]) (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 7AFEC1EEA40 for ; Wed, 18 Jun 2025 06:35:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.9 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750228534; cv=none; b=jf8wtcUFBaFm65Yn4oBg/MH+Quc+iPwhi8H9RkfDnRCyAeLGVwC8g4P9E8blR3WDM9B02M7BfXjb2OqxqR1dWfkq/MRoRKU4kgvXML19W7OW3imvU1z1L5+MFBljyuwsOeYH1XqNxnkh0HWBOUXi2fBjvkBxrBDYQ0NIcY42G3Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750228534; c=relaxed/simple; bh=aU27uou+GwvbZ3l+3mHzxna6LubemKb6KHdTutkk27I=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=rUhre8geQTJ83qEDwmbfIznO5wvcRPeWPr2LPBlTC0sBfnAL9zCjI88i8KdARhTHXYG87fJcaQC2s347759LiLuL+amc7JX8Fsh7HtphQ3JyqYweNjsefzvgWIzm6MFMd5TKOae777tO7B88hvXZARsZ2C8VILcJ2f7Xb1/vxb8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=none smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=Tf9LoSL/; arc=none smtp.client-ip=198.175.65.9 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="Tf9LoSL/" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1750228533; x=1781764533; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=aU27uou+GwvbZ3l+3mHzxna6LubemKb6KHdTutkk27I=; b=Tf9LoSL/umwp7H9ppG9b20Ig0NLfoblBC9IjKAK7/t9XXUq32kyb2Au0 4JgqTkmJO4gfjKpsbWQVRYTOlpmniJjIhYrvGqONaWc4xEQvlianqqc/J V8wvYxDgMzSeOyKAFOhzXR/8sGFL7zi1thBbnDD6vcIz7ENFbMMlhuoLS BV0//pUSV7uv91LjLxf5EEaFrAOHcOB5V3jI7Lc+ivsBdYPikB/MtWobi TSMmEC+V519u27OZ2ThZlbXMLZBdtPMZe+a2glc/510fCOce8TfqcBlkl SyP6GdP4HlbpM+7IkfMsM+8Oi5oJBb+iaxke5fz7w3cWdVXtOqEqw9He/ g==; X-CSE-ConnectionGUID: C0WjY9kgQheisSzqpnbuXw== X-CSE-MsgGUID: MloO7DBxS0CRhAgAZr9kQw== X-IronPort-AV: E=McAfee;i="6800,10657,11467"; a="74964348" X-IronPort-AV: E=Sophos;i="6.16,245,1744095600"; d="scan'208";a="74964348" Received: from fmviesa002.fm.intel.com ([10.60.135.142]) by orvoesa101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Jun 2025 23:35:32 -0700 X-CSE-ConnectionGUID: E+BkApjYRxG+wFCM6wmLJQ== X-CSE-MsgGUID: wYKmSwshRGqNe23ihUYBeQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.16,245,1744095600"; d="scan'208";a="172612510" Received: from mohdfai2-mobl.gar.corp.intel.com (HELO [10.247.50.4]) ([10.247.50.4]) by fmviesa002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Jun 2025 23:35:28 -0700 Message-ID: <3e458cbe-a251-4f25-b264-6d1d441604c7@linux.intel.com> Date: Wed, 18 Jun 2025 14:35:25 +0800 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next 5/7] igc: add private flag to reverse TX queue priority in TSN mode To: Vladimir Oltean , Paolo Abeni Cc: Tony Nguyen , faizal.abdul.rahim@intel.com, chwee.lin.choong@intel.com, horms@kernel.org, vitaly.lifshits@intel.com, dima.ruinskiy@intel.com, Mor Bar-Gabay , davem@davemloft.net, edumazet@google.com, andrew+netdev@lunn.ch, netdev@vger.kernel.org, kuba@kernel.org References: <20250611180314.2059166-1-anthony.l.nguyen@intel.com> <20250611180314.2059166-6-anthony.l.nguyen@intel.com> <26b0a6cd-9f2c-487a-bb7a-d648993b8725@redhat.com> <20250617121742.64no35fvb2bbnppf@skbuf> Content-Language: en-US From: "Abdul Rahim, Faizal" In-Reply-To: <20250617121742.64no35fvb2bbnppf@skbuf> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Hi Vladimir, Thanks for your feedback. On 17/6/2025 8:17 pm, Vladimir Oltean wrote: > Hi Paolo, > > On Tue, Jun 17, 2025 at 12:06:14PM +0200, Paolo Abeni wrote: >> On 6/11/25 8:03 PM, Tony Nguyen wrote: >>> To harmonize TX queue priority behavior between taprio and mqprio, and >>> to fix these issues without breaking long-standing taprio use cases, >>> this patch adds a new private flag, called reverse-tsn-txq-prio, to >>> reverse the TX queue priority. It makes queue 3 the highest and queue 0 >>> the lowest, reusing the TX arbitration logic already used by mqprio. >> Isn't the above quite the opposite of what Vladimir asked in >> https://lore.kernel.org/all/20250214113815.37ttoor3isrt34dg@skbuf/ ? >> >> """ >> I would expect that for uniform behavior, you would force the users a >> little bit to adopt the new TX scheduling mode in taprio, otherwise any >> configuration with preemptible traffic classes would be rejected by the >> driver. >> """ >> >> I don't see him commenting on later version, @Vladimir: does this fits you? > > Indeed, sorry for disappearing from the patch review process. > > I don't see the discrepancy between what Faizal implemented and what we > discussed. Specifically on the bit you quoted - patch "igc: add > preemptible queue support in taprio" refuses taprio schedules with > preemptible TCs if the user hasn't explicitly opted into > IGC_FLAG_TSN_REVERSE_TXQ_PRIO. If that private flag isn't set, > everything works as currently documented, just the new features are > gated. > > The name of the private flag is debatable IMHO, because it's taprio > specific and the name doesn't reflect that (mqprio uses the "reverse" > priority assignment to TX queues by default, and this flag doesn't > change that). Also, "reverse" compared to what? Both operating modes can Compared to the default Tx queue priority in TSN mode, where Tx q0 has the highest priority and q3 the lowest. My thinking behind the naming was based on how the relevant register fields are configured. Snippet of i226 documentation: "While in TSN mode each transmit queue is assigned a priority level by the TxQ_Priority fields in the TxARB register" "TxQ_Priority_0: The transmit queue that is assigned as priority 0 (highest priority). Default is queue 0" "TxQ_Priority_3: The transmit queue that is assigned as priority 3 (lowest priority). Default is queue 3." > equally be named "reverse". True — mqprio already uses the reverse mapping by default even without this private flag, which could feel inconsistent. > Maybe "taprio-standard-txq-priority" would > have been clearer regarding what the flag really does. I’m okay with that suggestion, though I’m not sure it makes things clearer. What’s considered “standard” may depend on context — for IGC users who haven’t worked with other NICs, the existing default priority mapping might feel like the standard. I’m definitely in favor of improving readability and maintenance, but I’m still unsure what name best reflects that balance.