From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Poor IPv6 TCP performance in 4.3-rc3 Date: Wed, 30 Sep 2015 00:32:53 +0100 Message-ID: <20150929233253.GS21513@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii To: netdev@vger.kernel.org Return-path: Received: from pandora.arm.linux.org.uk ([78.32.30.218]:56275 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750813AbbI2Xc7 (ORCPT ); Tue, 29 Sep 2015 19:32:59 -0400 Received: from n2100.arm.linux.org.uk ([fd8f:7570:feb6:1:214:fdff:fe10:4f86]:60290) by pandora.arm.linux.org.uk with esmtpsa (TLSv1:DHE-RSA-AES256-SHA:256) (Exim 4.82_1-5b7a7c0-XX) (envelope-from ) id 1Zh4OG-0006K8-Dk for netdev@vger.kernel.org; Wed, 30 Sep 2015 00:32:56 +0100 Received: from linux by n2100.arm.linux.org.uk with local (Exim 4.76) (envelope-from ) id 1Zh4OD-0007jw-Gd for netdev@vger.kernel.org; Wed, 30 Sep 2015 00:32:53 +0100 Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: Hi, I'm seeing really poor IPv6 performance compared to IPv4. I've checked using two different ARM platforms - an iMX6 platform using the FEC driver, and an Armada 38x using mvneta. The following was captured using iperf between the target system and my laptop. The problem only occurs one-way. The 4.3-rc3 platform is running iperf in server mode, the laptop is in client mode. Armada 38x: ipv6: [ 4] 0.0-23.9 sec 170 KBytes 58.3 Kbits/sec ipv4: [ 4] 0.0-10.0 sec 1.09 GBytes 936 Mbits/sec iMX6Q: ipv6: [ 4] 0.0-11.1 sec 640 KBytes 474 Kbits/sec ipv4: [ 4] 0.0-10.0 sec 655 MBytes 549 Mbits/sec iMX6D with 4.2: ipv6: [ 4] 0.0-10.0 sec 685 MBytes 574 Mbits/sec ipv4: [ 4] 0.0-10.0 sec 696 MBytes 583 Mbits/sec It looks like there's an IPv6 regression between 4.2 and 4.3-rc3. Turning GRO off on Armada 38x gives: ipv6: [ 4] 0.0-10.0 sec 1.08 GBytes 923 Mbits/sec ipv4: [ 5] 0.0-10.0 sec 1.09 GBytes 936 Mbits/sec I haven't started to debug yet, but I thought I'd post a heads-up in case it's a known problem. I'll try to get some packet logs on Thursday, and I'll try to bisect. -- FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.