From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from unimail.uni-dortmund.de (mx1.hrz.uni-dortmund.de [129.217.128.51]) (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 C1E873BE642; Tue, 7 Jul 2026 06:59:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=129.217.128.51 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783407572; cv=none; b=U1YHK8XjUhxA8Y1pXVH8Fm+nD83oj8TXSZIbgNQuvECrtNQTbTKlBtUsiVxhBjpJ9I350c5yVyXs7trioEIuyTg80AcTThwd455ToOAlkPIntXAg0YDJI6Mg+7JJlXdgSjvoZJHLR5I5P2rxL8tvud2nvX+fvHfm60308uTNsNU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783407572; c=relaxed/simple; bh=J5z4v8MnX37yvRsBRkrgJ7RXFCTxbHS1dIRgegQB26U=; h=Content-Type:Message-ID:Date:MIME-Version:Subject:From:To:Cc: References:In-Reply-To; b=SVtV9ZlG0siUCNW7r/KEQ9FDeZ6axKf+nl5yjo4npZ680SHBAttJGW6mmOAdP8Q3yOQQOJHNgiYRLC8F6LNfxBXEuBGr6I3yka6sOA5zXcJJ866BFPOvlXLgfR/3F+bPzgG9n1XKMv+i3ZzjpeIaUO/TGQ/oFyxY67N8tutOkIc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=tu-dortmund.de; spf=pass smtp.mailfrom=tu-dortmund.de; dkim=pass (1024-bit key) header.d=tu-dortmund.de header.i=@tu-dortmund.de header.b=gUqA1FTH; arc=none smtp.client-ip=129.217.128.51 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=tu-dortmund.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=tu-dortmund.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=tu-dortmund.de header.i=@tu-dortmund.de header.b="gUqA1FTH" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=tu-dortmund.de; s=unimail; t=1783407369; bh=kaPGdKlGO3D+peQmYigaO6QLSP3edbFA8eMgoOpcNKI=; h=Date:Subject:From:To:Cc:References:In-Reply-To; b=gUqA1FTHPEG8EOihHgfi4S46ixfVwWuEhwaIGk12dZXa1Q6q0/NBTneYiRU0jaegy n5ZdVJAtYbka1LfFD+vvIZIA3SiqGeT1N4A7oyqYbJK7VqAsmM12ZDGz28FXtqqO2h sINyMwK+N3NAPC7oKD/8BNNZ8PLRmpMX6NBlrOeM= Received: from [129.217.186.105] ([129.217.186.105]) (authenticated bits=0) by unimail.uni-dortmund.de (8.19.0.2/8.19.0.2) with ESMTPSA id 6676u7Zc022889 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Tue, 7 Jul 2026 08:56:08 +0200 (CEST) Content-Type: multipart/mixed; boundary="------------MskE5ndfay3xkFhLGVVkdWqb" Message-ID: <527f81a7-05da-4c01-b4fa-aa090c6f57ce@tu-dortmund.de> Date: Tue, 7 Jul 2026 08:56:07 +0200 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 v2] tun/tap & vhost-net: make qdisc backpressure opt-in via IFF_BACKPRESSURE From: Simon Schippers To: Brett A C Sheffield Cc: "Michael S. Tsirkin" , Willem de Bruijn , Jason Wang , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , netdev@vger.kernel.org, Simon Horman , Jonathan Corbet , Shuah Khan , Andrew Lunn , Tim Gebauer , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260706094242.115992-1-simon.schippers@tu-dortmund.de> <20260706091706-mutt-send-email-mst@kernel.org> <2728c540-2e76-4e06-9064-ed1dff071cbe@tu-dortmund.de> <0d28fdc4-3c03-48d6-bd59-e59f7a01f4b6@tu-dortmund.de> Content-Language: en-US In-Reply-To: <0d28fdc4-3c03-48d6-bd59-e59f7a01f4b6@tu-dortmund.de> This is a multi-part message in MIME format. --------------MskE5ndfay3xkFhLGVVkdWqb Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/7/26 08:52, Simon Schippers wrote: > Brett, can you try the two attached patches here with iperf3? > I think testing with 8 and 16 threads is enough, so where there is a > regression. > > The two patches are about time when to wake: > Currently we wake after consuming half the internal ring buffer. > One of the attached patches wakes after 2 cachelines (128 of 1000 > packets) and the other one just wakes once the ring buffer is empty. > > This would really help :) Whoops send you the wrong patch (the opt-in patch again), here is the wake on empty patch. --------------MskE5ndfay3xkFhLGVVkdWqb Content-Type: text/x-patch; charset=UTF-8; name="0001-tun-set-waking-threshold-to-ptr_ring_empty.patch" Content-Disposition: attachment; filename="0001-tun-set-waking-threshold-to-ptr_ring_empty.patch" Content-Transfer-Encoding: base64 RnJvbSBhNDM0MzkyMmU2MzVjYjFjYWIwMTdiMmU4NWNkZDJlNjA2Y2I2NjdhIE1vbiBTZXAg MTcgMDA6MDA6MDAgMjAwMQpGcm9tOiBTaW1vbiBTY2hpcHBlcnMgPHNpbW9uLnNjaGlwcGVy c0B0dS1kb3J0bXVuZC5kZT4KRGF0ZTogVHVlLCA3IEp1bCAyMDI2IDA4OjM4OjMxICswMjAw ClN1YmplY3Q6IFtQQVRDSF0gdHVuOiBzZXQgd2FraW5nIHRocmVzaG9sZCB0byBwdHJfcmlu Z19lbXB0eSgpCgpPbmx5IHdha2Ugb25jZSB0aGUgcHRyX3JpbmcgaXMgZW1wdHksIHdoaWNo IHJlc3VsdHMgaW4gbGF0ZXIgYW5kIGxlc3MKY2FsbHMgb2YgbmV0aWZfdHhfd2FrZV9xdWV1 ZSgpLgotLS0KIGRyaXZlcnMvbmV0L3R1bi5jIHwgMyArLS0KIDEgZmlsZSBjaGFuZ2VkLCAx IGluc2VydGlvbigrKSwgMiBkZWxldGlvbnMoLSkKCmRpZmYgLS1naXQgYS9kcml2ZXJzL25l dC90dW4uYyBiL2RyaXZlcnMvbmV0L3R1bi5jCmluZGV4IGZmYmU2ZjEzZmIxZi4uYWNiYWZk MzlmM2FlIDEwMDY0NAotLS0gYS9kcml2ZXJzL25ldC90dW4uYworKysgYi9kcml2ZXJzL25l dC90dW4uYwpAQCAtMjE1OCw4ICsyMTU4LDcgQEAgc3RhdGljIHZvaWQgX190dW5fd2FrZV9x dWV1ZShzdHJ1Y3QgdHVuX3N0cnVjdCAqdHVuLAogCXNtcF9tYigpOwogCWlmIChuZXRpZl90 eF9xdWV1ZV9zdG9wcGVkKHR4cSkpIHsKIAkJdGZpbGUtPmNvbnNfY250ICs9IGNvbnN1bWVk OwotCQlpZiAodGZpbGUtPmNvbnNfY250ID49IHRmaWxlLT50eF9yaW5nLnNpemUgLyAyIHx8 Ci0JCSAgICBfX3B0cl9yaW5nX2VtcHR5KCZ0ZmlsZS0+dHhfcmluZykpIHsKKwkJaWYgKF9f cHRyX3JpbmdfZW1wdHkoJnRmaWxlLT50eF9yaW5nKSkgewogCQkJbmV0aWZfdHhfd2FrZV9x dWV1ZSh0eHEpOwogCQkJdGZpbGUtPmNvbnNfY250ID0gMDsKIAkJfQotLSAKMi40My4wCgo= --------------MskE5ndfay3xkFhLGVVkdWqb--