Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751901AbaB0Uwa (ORCPT ); Thu, 27 Feb 2014 15:52:30 -0500 Received: from e06smtp12.uk.ibm.com ([195.75.94.108]:40019 "EHLO e06smtp12.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751522AbaB0Uw3 (ORCPT ); Thu, 27 Feb 2014 15:52:29 -0500 Message-ID: <530FA586.3010400@de.ibm.com> Date: Thu, 27 Feb 2014 21:52:22 +0100 From: Christian Borntraeger User-Agent: Mozilla/5.0 (X11; Linux i686; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 MIME-Version: 1.0 To: Vlad Yasevich CC: "David S. Miller" , Jason Wang , "Michael S. Tsirkin" , netdev@vger.kernel.org, KVM list , Linux Kernel Mailing List Subject: macvtap performance regression (bisected) between 3.13 and 3.14-rc1 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14022720-8372-0000-0000-000008D34EDD Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Vlad, commit 6acf54f1cf0a6747bac9fea26f34cfc5a9029523 macvtap: Add support of packet capture on macvtap device. causes a performance regression for iperf traffic between two KVM guests on my s390 system. Both guests are connected via two macvtaps on the same OSA network card. Before that patch I get ~20 Gbit/sec between two guests, afterwards I get ~4Gbit/sec Latency seems to be unchanges (uperf 1byte ping pong). According to ifconfig in the guest, I have ~ 1500 bytes per packet with this patch and ~ 40000 bytes without. So for some reason this patch causes the network stack to do segmentation. (the guest kernel stays the same, only host kernel is changed). Any ideas? Christian -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/