[Soekris] high CPU usage for network interrupts on 4801

Arnt Gulbrandsen arnt at gulbrandsen.priv.no
Mon Sep 17 08:19:55 UTC 2007


Maurice Janssen writes:
> On Sunday, September 16, 2007 at 21:26:36 +0000, Poul-Henning Kamp wrote:
>> The 4801 unfortunately has all three internal network cards on the 
>> same interrupt line, that's not a good thing because for every 
>> interrupt the kernel will have to check all three network interfaces 
>> to see where it came from.
>
> I'm by no means an expert on this subject, but others seem to think 
> that interrupt sharing is a good thing:
> http://mail-index.netbsd.org/tech-perform/2003/02/03/0000.html
> http://www.openbsd.org/faq/faq12.html#IrqShare

It depends. If the operating system in use has certain optimisations and 
misses certain others, it helps in some cases, including an important 
case. But in general, more precise information from the hardware to the 
OS helps the OS work faster, and "eth0 needs care now" is more precise 
than "either eth0, eth1, eth2 or a combination needs care now".

Arnt


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