[linux-help] Re: Dual processors

[Carl D Cravens <raven@xxxxxxxxxxx>]

On Sat, 10 Aug 2002, Anne McCadden wrote:

> I am running 3 sessions of Seti at the same time, use the pc to check my
> email, surf the web, download songs, have apache & mysql daemons in the
> background on a single 1.4 AMD thunderbird without any problems.

It's not like you have to have multiple CPUs to run multiple programs
without _problems_... but multiple CPUs when running lots of CPU-intensive
programs will certainly increase through-put.

Being that SETI@Home primarily does nothing but crunch numbers (very
little IO activity, so it's CPU-bound instead of IO-bound), what's the
point of running three sessions at once?  There's only so much CPU time to
go around, so dividing it among three sessions just gives less time to
each session. Having three sessions just means the kernel spends more time
swapping between programs and uses up more memory.  If it's a matter of
SETI getting more time than other programs, just 'renice' it to something
that'll make it a higher priority.  (Actually, I think you can specify a
'nice' value directly in SETI's configuration or command line options.)

I could be wrong, but I'm willing to bet that, on a single CPU, a single
session of SETI@Home at an appropriate priority will analyze packets
faster than three sessions run at the same time.  Probably an unmeasurable
amount faster, since swapping between running processes happens rather
quickly and eliminating just two processes won't make a noticable
difference.  But the point is, you should be able to run just one process
at a higher priority and get the same throughput as you would running
three at a default priority.

--
Carl D Cravens (raven@xxxxxxxxxxx)
This tagline made from 100% recycled ASCII.

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