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,=0A=0AIn theory, on a Gigabit link you get 1 000 000 000 bits * = second.=0ABy default you have the MTU set to 1500 bytes which makes ~12 000= bits.=0A1 000 000 000 / 12 000 =3D ~ 83 333 packets per second.=0A83 333 p= ackets per second makes 0.083333 packets per microsecond.=0A1 / 0.08333 =3D= 12.0 microseconds per packet. Thus one can interrupt CPU=0Aat a rate of ~8= 3 333 times per second. If you use lower packets sizes you =0Amight get eve= n more funny numbers.=0A=0A8000 is a quiet low number. The driver was devel= oped by guys=0Aat Intel. I don't see a reason to worry. =0A=0ABy the way th= ey have products with Interrupt Moderation.=0Ahttp://www.intel.com/design/n= etwork/applnots/ap450.htm=0A=0AThe question is really amazing. Thanks, it h= ave tickled me big time.=0A=0ASincerely,=0A=0ANash=0A=0A----- Original Mess= age ----=0AFrom: Jordi Espasa Clofent <jordi.espasa@opengea.org>=0ATo: free= bsd-net@freebsd.org=0ASent: Wednesday, December 26, 2007 12:12:55 PM=0ASubj= ect: Re: Maximum NIC interrupts=0A=0A=0AOK, I'll try to explain in another = way.=0A=0AWhile I've done network performance test I've monitored the IRQ r= ate, =0Aand, for example, it's a 7000/8000 interrupts per second in every N= IC=0A (I =0Ause 2 NICs in a bridge). The question is=0A=0A=BFhow can I know= if this irq rate is too high or not? =BFhow can I know=0A if =0AI'm closer= to device limits, or kernel limits?=0A=0AI want to say that I'm don't know= if 8000 irq per second means a high =0AIRQ use or a lower user.=0A=0AI hop= e I've explained better at this time.=0A=0A-- =0AThanks,=0AJordi Espasa Clo= fent=0A_______________________________________________=0Afreebsd-net@freebs= d.org mailing list=0Ahttp://lists.freebsd.org/mailman/listinfo/freebsd-net= =0ATo unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org"= =0A=0A=0A=0A=0A=0A=0A ________________________________________________= ____________________________________=0ANever miss a thing. Make Yahoo your= home page. =0Ahttp://www.yahoo.com/r/hs
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