From owner-freebsd-hackers Mon Mar 19 11:33: 3 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from herbelot.dyndns.org (s014.dhcp212-24.cybercable.fr [212.198.24.14]) by hub.freebsd.org (Postfix) with ESMTP id DC45037B719 for ; Mon, 19 Mar 2001 11:32:59 -0800 (PST) (envelope-from thierry@herbelot.com) Received: from herbelot.com (multi.herbelot.nom [192.168.1.2]) by herbelot.dyndns.org (8.9.3/8.9.3) with ESMTP id UAA61747; Mon, 19 Mar 2001 20:32:26 +0100 (CET) (envelope-from thierry@herbelot.com) Message-ID: <3AB65EC9.4D969490@herbelot.com> Date: Mon, 19 Mar 2001 20:32:25 +0100 From: Thierry Herbelot X-Mailer: Mozilla 4.76 [en] (X11; U; Linux 2.2.12 i386) X-Accept-Language: en MIME-Version: 1.0 To: =?iso-8859-1?Q?M=E5rten=20Wikstr=F6m?= Cc: "'freebsd-hackers@freebsd.org'" Subject: Re: Routing latency References: Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Hello, the FreeBSD TCP/IP stack uses the "system tick timer" for some delay (maybe only for TCP). you may want to use a HZ=1000 option (see the LINT config file) in a recompiled kernel and see if things go better. (moreover, the dc(4) driver which is used for your NIC has some interesting performance improvements in the forthcoming 4.3-Release) TfH Mårten Wikström wrote: > > I've performed a routing test between a FreeBSD box and a Linux box. I > measured the latency and the result was not what I had expected. Both > systems had the peak at 100 us (microseconds), but whereas the Linux box had > _no_ packet over 200 us, the FreeBSD box delayed some packets up to 2 ms! > Looking at the time series, it seems that the packets are delayed at regular > intervals, about every second. My guess is that some timer interrupt > triggers every second and steals too much cpu. So my question is, how can I > decrease this routing delay? > > Test info: > I used two identical boxes, each equipped with a Pentium Pro 200Mhz and 64Mb > mem. RedHat 7.0 with 2.4 kernel in one and FreeBSD 4.2-RELEASE in the other. > I used two DEC 100Mbit ethernet cards (21140 I think). > I measured the latency with a SmartBits instrument. Fastforwarding was > disabled. Three UDP streams was sent from the SmartBits to one of the > ethernet cards in the box, which routed the streams to the other interface, > which in turn was connected back to the SmartBits. > I had not made any changes to the standard kernel configuration. No other > processes was running in the background, apart from those necessary to > perform the test. The ARP table was set statically, so no ARP traffic would > disturb. > > I would at least want to know what is causing the extra delays. > > /Mårten > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-hackers" in the body of the message -- Thierry Herbelot To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message