nanog mailing list archives
Re: Software router state of the art
From: Petri Helenius <petri () helenius fi>
Date: Sun, 27 Jul 2008 09:12:58 +0300
William Herrin wrote:
The driver provides the adapter a ring buffer of memory locations to busmaster dma the data into (which does not require interrupting the CPU). The interrupts are triggered after the DMA completes and in moderation controllable by the driver. For FreeBSD the default maxes interrupts out at 8000 per second and on some of the adapters there are firmware optimizations for lowering the latency from the obvious maximum of 125 microseconds. When an interrupt is fired the driver restocks the ring buffer with new addresses to put data into, for one or for 4000 frames, depending on how many were used up.The pro/1000 does not need to generate an interrupt in order to start a DMA transfer? Can you refer me to some documents which explain in detail how a card on the bus sets up a DMA transfer?
With IOAT and various offloads this gets somewhat more complicated and more effective.
Pete
Current thread:
- Re: https (was: Re: Exploit for DNS Cache Poisoning - RELEASED), (continued)
- Re: https (was: Re: Exploit for DNS Cache Poisoning - RELEASED) Jim Popovitch (Jul 25)
- Re: https Patrick Giagnocavo (Jul 31)
- Re: https (was: Re: Exploit for DNS Cache Poisoning - RELEASED) Jasper Bryant-Greene (Jul 24)
- Re: https (was: Re: Exploit for DNS Cache Poisoning - RELEASED) William Pitcock (Jul 24)
- Re: https (was: Re: Exploit for DNS Cache Poisoning - RELEASED) Chris Adams (Jul 24)
- Re: https Ken A (Jul 24)
- Re: Exploit for DNS Cache Poisoning - RELEASED Tuc at T-B-O-H.NET (Jul 23)
- Re: Software router state of the art Petri Helenius (Jul 26)
- Re: Software router state of the art William Herrin (Jul 26)
- Re: Software router state of the art Florian Weimer (Jul 26)
- Re: Software router state of the art Petri Helenius (Jul 26)
- Re: Software router state of the art Florian Weimer (Jul 26)
- Re: Software router state of the art Joel Jaeggli (Jul 23)
- Re: Software router state of the art Chris Adams (Jul 26)
- Re: Software router state of the art Seth Mattinen (Jul 26)
- RE: Software router state of the art Darden, Patrick S. (Jul 28)