On 02-May-2002 Jonathan Mini wrote:
> John Baldwin [jhb@FreeBSD.org] wrote :
>
>>
>> On 01-May-2002 Jonathan Mini wrote:
>> > Andrew Gallatin [gallatin@cs.duke.edu] wrote :
>> >> > No, the interrupts seem to be round-robin, but each clock intr is only
>> >> > sent to one CPU unlike on alpha where they are broadcast.
>> >>
>> >> So each CPU gets (1/num_cpu) * hz clock interrupts/sec?
>> >
>> > Yes, but because the timer is set to num_cpu*hz, each CPU ends up getting
>> > the normal hz interrupts. That's why it runs round-robin but looks like a
>> > broadcast.
>>
>> Eh, are you talking about the Alpha? On x86 we don't do this and have to
>> use
>> IPI's to simulate a broadcast-type deal.
>>
>
> I am obviously thinking about some other SMP implementation, but I have no
> idea which one. Somebody, somewhere, sets the routing of the clock interrupt
> to be delivered in a round-robin fashion, and then multiplies the clock
> frequency by the number of processors. They're really proud of this solution,
> because (they claim) it reduces contentions of clock-triggered events across
> processors.
It probably does.
> Maybe it was Sun?
Maybe? On the alpha it is very nice, because not only is it broadcast, but
it's broadcast in a staggered fashion, so not all CPU's get the clock interrupt
at the same time, thus reducing contention.
--
John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!" - http://www.FreeBSD.org/
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