Date: Mon, 19 Mar 2001 15:22:56 +0100 From: =?iso-8859-1?Q?M=E5rten_Wikstr=F6m?= <Marten.Wikstrom@framfab.se> To: "'freebsd-hackers@freebsd.org'" <freebsd-hackers@freebsd.org> Subject: Routing latency Message-ID: <E6D22E487D45D411931B00508BCF93E75C0330@storeg001.framfab.se>
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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. /M=E5rten To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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