You're assuming that you run 1 thread at a 2 to 4 core node or so?
This is not the reality.
See supercomputer report Europe. On average of machines in production more
than 50% of the cpu's is on average in use and that
goes up to 70% on average at every given hour 24 hours a day, 365 days a
year.
So even if you start your program as a single thread a node (note why make
your program MPI when you have idle cores in this node),
even in that unlikely case, the odds is 70% some other job runs at that same
node as well eating the other core(s).
Vincent
----- Original Message -----
From: "Eric W. Biederman" <[EMAIL PROTECTED]>
To: "Vincent Diepeveen" <[EMAIL PROTECTED]>
Cc: "Ashley Pittman" <[EMAIL PROTECTED]>; "'Bogdan Costescu'"
<[EMAIL PROTECTED]>; "'Beowulf List'"
<beowulf@beowulf.org>; "Daniel Kidger" <[EMAIL PROTECTED]>;
"'Mark Hahn'" <[EMAIL PROTECTED]>
Sent: Saturday, September 09, 2006 3:49 AM
Subject: Re: [Beowulf] cluster softwares supporting parallel CFD computing
"Vincent Diepeveen" <[EMAIL PROTECTED]> writes:
How about the latency to wake up that thread again. runqueue latency in
linux is
10+ ms?
That assumes you have a 100Mhz clock (default is currently 250Mhz) and
you have something else running. If you have something else running
yielding is even more of a win because you get something productive
done, when you would otherwise be idle. Plus you the scheduler
will give your process a higher priority when it wakes up because
it slept.
In practice I don't expect anything interesting will happen in that time
interval. So you should awake almost instantly.
Eric
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