Re: [SLE] For or against ..Hyperthreading.
From: Bruce Marshall (bmarsh_at_bmarsh.com)
Date: 08/31/03
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To: SLE <suse-linux-e@suse.com> Date: Sun, 31 Aug 2003 11:54:50 -0400
On Sunday 31 August 2003 4:36 am, John Andersen wrote:
> On Saturday 30 August 2003 12:32, Bruce Marshall wrote:
> > I'll take a single cpu any day over multiple cpu's that DON'T ADD UP
> > TO MORE MIPS than the single cpu. And that was my point.
>
> A very well reasond answer Bruce.
>
> Unfortunatly it just proves you have never touched a Dual CPU machine
> running and SMP kernel in your life.
>
Wrong.... Both SMP PC's and IBM mainframes with up to 5 engines....
> Because in spite of your reasoning, the facts are the opposite.
>
> ANYONE who has used dualies would tell you two 500hmz CPUs
> easliy outperform a single 1Ghz cpu on the normal mix
> of applications you run on a typical linux machine, and they do it for
> LESS money. Usually enough less to afford the
> dual motherboard.
>
And that's got to be a crock.... So, for example, I'll get more SETI
work done on the above SMP machine? I'd like to see you prove it.
Define 'normal mix' for a single user machine.
> CPU time is hardly ever the bottelneck in computers
> these days, except on the most compute intensive task.
>
You're right on that...
> You assume in your SETI example that the CPU doing
> updatedb does nothing else except the updatedb. That's not
> true, it can run SETI while it is waiting on diskIO.
>
Uhhh... that was my point... With an SMP machine, you're going to have
1 cpu running SETI and 1 cpu doing the updatedb... Not always the same
cpu doing either, but in general, 1 for each. Now if you want to run 2
SETI programs, then you would be applying 2 cpus to SETI, and both
would keep the updatedb running with what little cpu power it needs.
But where are you gaining in the SETI area? 2 cpu' at 1Ghz are not
going to be any better than 1 cpu at 2Ghz. If you think so, please
explain where the cycles are coming from.
> Instruction fetch takes longer than instruction execution
> by several orders of magnitude. With two CPUs
> fetching data and instructions tasks are seldom ever
> backed up, and the machine remains responsive
> even under high load.
>
Wow, that's a stretch...
> A load of 50 would burry most single processor machines
> yet I've seen that often on a busy dual processor machine
> and it just runs right thru it.
>
Pure perception if you think the above is the case.
> In all but the most compute intensive tasks I'll take
> two half speed CPUs over a single full-speed
> one any day.
>
It's your choice.
> I ran RC5 crunchers in several of my machines for several
> years. The dualies (running two curnchers) always
> outperformed Single CPU machines twice their speed
> even though they theoretically should not have had an
> advantage on such a compute intensive task.
>
> If you're baseing your theory on Win2k or NT platforms you'd be
> right, Windows can only get 1.4 times a single processor
> performance with dual processors. Linux gets 2x.
>
> And when you want to do an addtionial task theres always
> a cpu cycle available - never any sluggish preformance.
>
> Don't theorize. Go get a dualie and bench it.
>
I've had one... not worth the extra expense......
> --
> _____________________________________
> John Andersen
-- +----------------------------------------------------------------------------+ + Bruce S. Marshall bmarsh@bmarsh.com Bellaire, MI 08/31/03 11:47 + +----------------------------------------------------------------------------+ "He knows nothing: he thinks he knows everything- that clearly points to a political career." --George Bernard Shaw -- Check the headers for your unsubscription address For additional commands send e-mail to suse-linux-e-help@suse.com Also check the archives at http://lists.suse.com Please read the FAQs: suse-linux-e-faq@suse.com
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