Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755550AbbDIPtG (ORCPT ); Thu, 9 Apr 2015 11:49:06 -0400 Received: from smtp02.citrix.com ([66.165.176.63]:48248 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753716AbbDIPtD (ORCPT ); Thu, 9 Apr 2015 11:49:03 -0400 X-IronPort-AV: E=Sophos;i="5.11,550,1422921600"; d="scan'208";a="253583716" Date: Thu, 9 Apr 2015 16:46:30 +0100 From: Stefano Stabellini X-X-Sender: sstabellini@kaball.uk.xensource.com To: CC: , , Stefano Stabellini , , Ian Campbell , "Wei Liu" , David Vrabel , , Konrad Rzeszutek Wilk Subject: "tcp: refine TSO autosizing" causes performance regression on Xen Message-ID: User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" X-DLP: MIA2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 896 Lines: 30 Hi all, I found a performance regression when running netperf -t TCP_MAERTS from an external host to a Xen VM on ARM64: v3.19 and v4.0-rc4 running in the virtual machine are 30% slower than v3.18. Through bisection I found that the perf regression is caused by the prensence of the following commit in the guest kernel: commit 605ad7f184b60cfaacbc038aa6c55ee68dee3c89 Author: Eric Dumazet Date: Sun Dec 7 12:22:18 2014 -0800 tcp: refine TSO autosizing A simple revert would fix the issue. Does anybody have any ideas on what could be the cause of the problem? Suggestions on what to do to fix it? Cheers, Stefano -- 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/