From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bregans-0.gladserv.net (bregans-0.gladserv.net [185.128.210.58]) (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 9266A3B9D9E; Tue, 7 Jul 2026 20:06:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.128.210.58 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783454781; cv=none; b=fbx47/HJ6L4cPlXr69jrdBDLK1NBaCDR5oReexNTcv9K5lKJ+sdbTWTiTOnDrmHQwEFyekGXDSFRK+Omy+xZlXvv72ZuJgeD5vGB0zRhGNDr/ezKNryRn6CvpcL1GNB1pvPzUp3ivVOpYm24ZPxdk5x2kp80G4pLqla26YMX0Ak= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783454781; c=relaxed/simple; bh=WYqFwOi8quQy3Uk+VrFiQW/eZL0UWoAEItTKR3fuMzU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Fy8TqWheW8kwIolC9mWpORCFQdMbKhyFh/Jx477/vuAMWS6Wiw2FxCuqca+Bg0MDUVifLgpXcm34pkLwF4KIew60wTHGzAr6Yn9EymHxgrGES57kpWVjiL7Uu82MGZVyZIGPX2/v3pb/XHi+g3+ey+hxaj2ZCuileydb+YHcRgo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=librecast.net; spf=pass smtp.mailfrom=librecast.net; arc=none smtp.client-ip=185.128.210.58 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=librecast.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=librecast.net Date: Tue, 7 Jul 2026 22:05:52 +0200 From: Brett A C Sheffield To: Simon Schippers 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 Subject: Re: [PATCH net v2] tun/tap & vhost-net: make qdisc backpressure opt-in via IFF_BACKPRESSURE Message-ID: 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> Precedence: bulk X-Mailing-List: linux-doc@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: <0d28fdc4-3c03-48d6-bd59-e59f7a01f4b6@tu-dortmund.de> On 2026-07-07 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 :) Sure... 7.2.0-rc2 (unpatched) threads 1 [ 5] 0.00-10.00 sec 20.4 GBytes 17.5 Gbits/sec 0 sender [ 5] 0.00-10.00 sec 2.00 GBytes 1.72 Gbits/sec receiver threads 2 [SUM] 0.00-10.00 sec 12.7 GBytes 10.9 Gbits/sec 0 sender [SUM] 0.00-10.00 sec 4.00 GBytes 3.43 Gbits/sec receiver threads 8 [SUM] 0.00-10.00 sec 11.5 GBytes 9.85 Gbits/sec 0 sender [SUM] 0.00-10.01 sec 11.4 GBytes 9.83 Gbits/sec receiver threads 16 [SUM] 0.00-10.00 sec 11.6 GBytes 9.95 Gbits/sec 0 sender [SUM] 0.00-10.01 sec 11.5 GBytes 9.91 Gbits/sec receiver 7.2.0-rc2 with 0001-tun-set-waking-threshold-to-ptr_ring_empty.patch threads 1 [ 5] 0.00-10.00 sec 19.6 GBytes 16.8 Gbits/sec 0 sender [ 5] 0.00-10.00 sec 2.00 GBytes 1.72 Gbits/sec receiver threads 2 [SUM] 0.00-10.00 sec 11.1 GBytes 9.50 Gbits/sec 0 sender [SUM] 0.00-10.00 sec 4.00 GBytes 3.43 Gbits/sec receiver threads 8 [SUM] 0.00-10.00 sec 10.8 GBytes 9.25 Gbits/sec 0 sender [SUM] 0.00-10.01 sec 10.7 GBytes 9.23 Gbits/sec receiver threads 16 [SUM] 0.00-10.00 sec 10.9 GBytes 9.34 Gbits/sec 0 sender [SUM] 0.00-10.01 sec 10.8 GBytes 9.30 Gbits/sec receiver 7.2.0-rc2 with 0001-tun-set-waking-threshold-to-tx_ring.batch.patch threads 1 [ 5] 0.00-10.00 sec 19.6 GBytes 16.9 Gbits/sec 2 sender [ 5] 0.00-10.00 sec 2.00 GBytes 1.72 Gbits/sec receiver threads 2 [SUM] 0.00-10.00 sec 13.9 GBytes 11.9 Gbits/sec 0 sender [SUM] 0.00-10.00 sec 4.00 GBytes 3.43 Gbits/sec receiver threads 8 [SUM] 0.00-10.00 sec 12.7 GBytes 10.9 Gbits/sec 0 sender [SUM] 0.00-10.01 sec 12.3 GBytes 10.6 Gbits/sec receiver threads 16 [SUM] 0.00-10.00 sec 12.5 GBytes 10.7 Gbits/sec 0 sender [SUM] 0.00-10.00 sec 12.4 GBytes 10.7 Gbits/sec receiver HTH, Brett -- Brett Sheffield (he/him) Librecast - Decentralising the Internet with Multicast https://librecast.net/ https://blog.brettsheffield.com/