From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S268346AbUHXD5H (ORCPT ); Mon, 23 Aug 2004 23:57:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S269001AbUHXD5H (ORCPT ); Mon, 23 Aug 2004 23:57:07 -0400 Received: from relay.pair.com ([209.68.1.20]:36625 "HELO relay.pair.com") by vger.kernel.org with SMTP id S268346AbUHXD5A (ORCPT ); Mon, 23 Aug 2004 23:57:00 -0400 X-pair-Authenticated: 66.190.51.173 Message-ID: <412ABC8B.5080608@cybsft.com> Date: Mon, 23 Aug 2004 22:56:59 -0500 From: "K.R. Foley" User-Agent: Mozilla Thunderbird 0.7.3 (X11/20040803) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Lee Revell CC: Ingo Molnar , linux-kernel Subject: Re: [patch] voluntary-preempt-2.6.8.1-P8 References: <20040816040515.GA13665@elte.hu> <1092654819.5057.18.camel@localhost> <20040816113131.GA30527@elte.hu> <20040816120933.GA4211@elte.hu> <1092716644.876.1.camel@krustophenia.net> <20040817080512.GA1649@elte.hu> <20040819073247.GA1798@elte.hu> <20040820133031.GA13105@elte.hu> <20040820195540.GA31798@elte.hu> <20040821140501.GA4189@elte.hu> <20040823210151.GA10949@elte.hu> <1093312154.862.17.camel@krustophenia.net> In-Reply-To: <1093312154.862.17.camel@krustophenia.net> X-Enigmail-Version: 0.85.0.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Lee Revell wrote: > On Mon, 2004-08-23 at 17:01, Ingo Molnar wrote: > > >> - reduce netdev_max_backlog to 8 (Mark H Johnson) >> > > > On my system this setting has absolutely no effect on the skb related > latencies. I tested setting netdev_max_backlog to every power of two > between 1 and 128, and regardless of this setting, I can produce a > 450-600 usec latency with: > > ping -s 65507 -f $DEFAULT_GATEWAY > > Looks like skb_checksum is the problem. Here is one of the traces: > > http://krustophenia.net/testresults.php?dataset=2.6.8.1-P8#/var/www/2.6.8.1-P8/trace14.txt > > Lee > > - Setting netdev_max_backlog doesn't seem to have any effect for me either. I get a similar latency when I try to reproduce your result above, ~612 usec. However, my trace is very different than yours: http://www.cybsft.com/testresults/2.6.8.1-P8/latency_trace3.txt In fact most any network activity, with the POSSIBLE exception of already open connections, seem to be able to trigger higher latencies. As you can see here: http://www.cybsft.com/testresults/2.6.8.1-P8/ kr