[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.
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