From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S266514AbUHXFCq (ORCPT ); Tue, 24 Aug 2004 01:02:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S266527AbUHXFCp (ORCPT ); Tue, 24 Aug 2004 01:02:45 -0400 Received: from mustang.oldcity.dca.net ([216.158.38.3]:54208 "HELO mustang.oldcity.dca.net") by vger.kernel.org with SMTP id S266514AbUHXFCm (ORCPT ); Tue, 24 Aug 2004 01:02:42 -0400 Subject: Re: [patch] voluntary-preempt-2.6.8.1-P8 From: Lee Revell To: "K.R. Foley" Cc: Ingo Molnar , linux-kernel In-Reply-To: <412ABC8B.5080608@cybsft.com> 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> <412ABC8B.5080608@cybsft.com> Content-Type: text/plain Message-Id: <1093323762.817.3.camel@krustophenia.net> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 Date: Tue, 24 Aug 2004 01:02:42 -0400 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2004-08-23 at 23:56, K.R. Foley wrote: > 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 > I have some that are similar to this. Looks like many of the differences are due to different network drivers (e100 vs via-rhine). > 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/ > Looks like except for the one above, all of these involve the extract_entropy issue. I am using a hack to disable the random driver to avoid these latencies. There are a few other threads going on discussing a real solution to the extract_entropy issue. However, none of the solutions that has been posted yet fix the problem. Lee