----- Original Message -----
From: "Eric W. Biederman" <[EMAIL PROTECTED]>
To: "Ashley Pittman" <[EMAIL PROTECTED]>
Cc: "'Bogdan Costescu'" <[EMAIL PROTECTED]>; "'Beowulf
List'" <beowulf@beowulf.org>; "Daniel Kidger"
<[EMAIL PROTECTED]>; "'Mark Hahn'" <[EMAIL PROTECTED]>
Sent: Thursday, September 07, 2006 7:54 PM
Subject: Re: [Beowulf] cluster softwares supporting parallel CFD computing
Ashley Pittman <[EMAIL PROTECTED]> 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
How about the latency to wake up that thread again. runqueue latency in
linux is 10+ ms?
Vincent
_______________________________________________
Beowulf mailing list, Beowulf@beowulf.org
To change your subscription (digest mode or unsubscribe) visit
http://www.beowulf.org/mailman/listinfo/beowulf
_______________________________________________
Beowulf mailing list, Beowulf@beowulf.org
To change your subscription (digest mode or unsubscribe) visit
http://www.beowulf.org/mailman/listinfo/beowulf
