[Beowulf] cluster softwares supporting parallel CFD computing

Eric W. Biederman ebiederm at xmission.com
Thu Sep 7 14:54:10 EDT 2006


Ashley Pittman <ashley at quadrics.com> writes:

> I think Daniel was talking about supercomputer networks and not
> ethernet, on the first QsNet2 machine I have to hand latency without
> interrupts is 2.72uSec, using interrupts it is 7.20uSec.  One
> fundamental difference between these two measurements is that when you
> use interrupts the kernel has to get involved, without interrupts it
> doesn't so you don't just have the interrupt but also a extra syscall.
>
> I know of people who have tried to tune the Hz rate down as low as 10,
> I'm fairly sure they wrote a paper about it.

Ok.  Those numbers sound believable.  Although they feel a little high,
which probably just means no one has done any serious tuning there.

At 5us latency after polling for just a short while you can likely
go to sleep without experiencing any real penalty.  Say within a milisecond
or so of polling you can sleep.

Eric
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