From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin LaHaise Subject: lots of cpu time spent in skb_copy_bits() in net-next with small mtu Date: Fri, 12 Jun 2009 12:13:20 -0400 Message-ID: <20090612161320.GB4290@neterion.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii To: netdev@vger.kernel.org Return-path: Received: from barracuda.s2io.com ([72.1.205.138]:42668 "EHLO barracuda.s2io.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751996AbZFLQQY (ORCPT ); Fri, 12 Jun 2009 12:16:24 -0400 Received: from guinness.s2io.com (localhost [127.0.0.1]) by barracuda.s2io.com (Spam Firewall) with ESMTP id 67196201E870 for ; Fri, 12 Jun 2009 12:13:23 -0400 (EDT) Received: from guinness.s2io.com (142-46-210.147.tel-ott.com [142.46.210.147]) by barracuda.s2io.com with ESMTP id 32t3RcVIoCsRW143 for ; Fri, 12 Jun 2009 12:13:23 -0400 (EDT) Received: from neterion.com ([10.16.18.39]) by guinness.s2io.com (8.12.6/8.12.6) with ESMTP id n5CGDLmd014584 for ; Fri, 12 Jun 2009 12:13:22 -0400 (EDT) Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: Hi folks, Just a heads up: something in net-next is resulting in lots of cpu time being spent in skb_copy_bits() (called from tcp_collapse()) when an ethernet interface mtu is lowered to 576 on the source and dest machines running netperf. This behaviour does not appear in 2.6.29. I'll try to bisect it this weekend. -ben