From owner-freebsd-hackers Sat Mar 31 1:18:33 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from max5.rrze.uni-erlangen.de (max5.rrze.uni-erlangen.de [131.188.3.50]) by hub.freebsd.org (Postfix) with ESMTP id 910AB37B722 for ; Sat, 31 Mar 2001 01:18:29 -0800 (PST) (envelope-from Jochen.Kaiser@rrze.uni-erlangen.de) Received: from devil.rrze.uni-erlangen.de by max5.rrze.uni-erlangen.de with ESMTP; Sat, 31 Mar 2001 11:18:27 +0200 Received: (from unrza2@localhost) by devil.rrze.uni-erlangen.de (8.9.3/8.9.3) id LAA08058; Sat, 31 Mar 2001 11:14:28 +0200 (CEST) From: Jochen Kaiser Date: Sat, 31 Mar 2001 11:14:27 +0200 To: FreeBSD-hackers@FreeBSD.ORG Cc: luigi@info.iet.unipi.it Subject: unexpected peaks in dummynet;scheduling oddity? Message-Id: <20010331111427.A3209@devil.rrze.uni-erlangen.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 1.0.1i Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Hello, I did some measurements using Dummynet. It was just to see how it works. Tests are made with 0,7MBit stream (each 429Bytes Packets), 5,10,15,25,50 and 75 MBit. I tried a delay of 10ms for the testing connection. The tests were done with a Smartbits6000 with the capability to record the difference between sending and receiving a packet. Each test had a 8192 packets. The result show a strange behaviour, depending on the data rate. _ | | vs. /\ 0.7MBit - 15MBit: diffuse, fairly hig variance from 9.5 - 10.3ms 25 MBit: between 50MBit - 75MBit: very sharp, extreme precise, delivers a nearly 10ms (variance not calculated yet ... to be done ..) I am now a bit confused. Is it a matter of scheduling? Maybe too much fairness for such tasks :) Or is it some kind of prediction in dummynet which favours high data rates. I think I've seen something like that for packet loss in dummynet. Any opionions appreciated. Maybe I did something wrong and forget to set some sysctl properly. with kind regards, Jochen Kaiser -- Jochen Kaiser kind@IRCNET, phone +49 9131 85-28134 Network Administration mailto:jochen.kaiser@rrze.uni-erlangen.de Regionales Rechenzentrum Universitaet Erlangen-Nuernberg, Germany GPG public key: http://www.uni-erlangen.de/~unrza2/public_key.txt To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message