[Beowulf] Computation on the head node
Peter St. John
peter.st.john at gmail.com
Tue May 20 14:54:18 PDT 2008
Just fwiw, as something of an outsider, I wasn't able to meaningfully parse
On 5/19/08, Jeffrey B. Layton <laytonjb at charter.net> wrote:
> Perry E. Metzger wrote:
>> "Jeffrey B. Layton" <laytonjb at charter.net> writes
>>> In any case, let me note the most important rule: if your CPUs aren't
>>>> doing work most of the time, you're not allocating resources
>>>> properly. If the task is really I/O bound, there is no point in having
>>>> more CPU than I/O can possibly manage. You're better off having 1/2th
>>>> the number of nodes with gargantuan amounts of cache memory than
>>>> having CPUs that are spending 80% of their time twiddling their
>>>> thumbs. The goal is to have the CPUs crunching 100% of the time, and
>>>> if they're not doing that, you're not doing things as well as you can.
>>> I absolutely disagree.
>> Chacun a son gout. I was under the impression that in scientific
>> computing the name of the game was having your computation done as
>> fast as possible at the lowest possible cost.
>> If your CPU is idle, why did you pay for it? They're a huge cost
>> differential these days between fast and slow CPUs. Why didn't you buy
>> a much cheaper CPU that would remain nearly 100% busy while keeping
>> the I/O subsystem as fast? You would have saved lots of cash, your job
>> would be done just as fast, and probably (in a modern system) you
>> would have saved a whole lot of electricity because slower CPUs eat
>> fewer Watts.
> Evidently you don't know jack about real codes. In addition, I've gotten
> some off-list messages that you have already been added to a number of
> kill files as a troll because of you inability to listen, understand, and
> plus your off-list obnoxious emails. I've joined the gang in adding you to
> kill file. Enjoy.
> I believe you're thinking of local IO - like a desktop.
>> No, really, I'm not.
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