Date: Wed, 26 Dec 2007 08:10:30 -0800 (PST) From: Nash Nipples <trashy_bumper@yahoo.com> To: freebsd-net@freebsd.org Subject: Re: Maximum NIC interrupts Message-ID: <508610.85778.qm@web36309.mail.mud.yahoo.com>
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Dear Jordi, In theory, on a Gigabit link you get 1 000 000 000 bits * second. By default you have the MTU set to 1500 bytes which makes ~12 000 bits. 1 000 000 000 / 12 000 = ~ 83 333 packets per second. 83 333 packets per second makes 0.083333 packets per microsecond. 1 / 0.08333 = 12.0 microseconds per packet. Thus one can interrupt CPU at a rate of ~83 333 times per second. If you use lower packets sizes you might get even more funny numbers. 8000 is a quiet low number. The driver was developed by guys at Intel. I don't see a reason to worry. By the way they have products with Interrupt Moderation. http://www.intel.com/design/network/applnots/ap450.htm The question is really amazing. Thanks, it have tickled me big time. Sincerely, Nash ----- Original Message ---- From: Jordi Espasa Clofent <jordi.espasa@opengea.org> To: freebsd-net@freebsd.org Sent: Wednesday, December 26, 2007 12:12:55 PM Subject: Re: Maximum NIC interrupts OK, I'll try to explain in another way. While I've done network performance test I've monitored the IRQ rate, and, for example, it's a 7000/8000 interrupts per second in every NIC (I use 2 NICs in a bridge). The question is ¿how can I know if this irq rate is too high or not? ¿how can I know if I'm closer to device limits, or kernel limits? I want to say that I'm don't know if 8000 irq per second means a high IRQ use or a lower user. I hope I've explained better at this time. -- Thanks, Jordi Espasa Clofent _______________________________________________ freebsd-net@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" ____________________________________________________________________________________ Never miss a thing. Make Yahoo your home page. http://www.yahoo.com/r/hs
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