🚀 go-pugleaf

So what's the point? I started this thread with an initial post that
had a very important disclaimer right up front:

	"The work done by Tomohiro Kawada and others has been
	interesting. I can think of a number of applications
	where dual/quad overclocked Celeron's can produce very
	cost effective clusters for number crunching. The crypt
	cracking teams will get a great windfall from this work."

There are many small working set applications that will have a big
win on SMP Celerons, possibly including yours. There are also some
medium working set applications with well localized accesses and
sequential memory accesses that will perform well too ... like gcc.

There are also many medium working set applications that would run
much faster on your quad PPro simply because of the 128K to 256K L2
cache size increase, and some significant common cases where dual
Celerons will fall on their face due to excessive memory contention
and L2 cache thrashing.

I started this thread simply to raise the issue that people need to
think about properly fiting their application to the hardware
architecture ... Dual Celerons are not a one size fits all SMP design,
dispite the testimonials of how well they work in some cases. SMP and
NUMA multi-processing has many suprises, one of which is that sometimes
applications run much faster, on the same hardware, when the second
processor is disabled. Any SMP or CC-NUMA performance guy with
significant experience has seen this at least once, and sometimes
more often than the industry would like to talk about.

In article <ulnebvpff.fsf@res.raytheon.com>,
  Johan Kullstam <kullstam@ne.mediaone.net> wrote:
> Totally Lost <idletime@my-dejanews.com> writes:
>
> > Linux is not well multi-threaded, and has a pretty large foot print
> > with very little locality in either the OS or it's primary
applications.
> > I would expect that for many users, dual Celeron's may have a
negative
> > performance impact much of the time.
> >
> > To observe that Dual Celron's produce an observed improvement under
> > certain lightly loading applications may be true. To assert that
> > they scale under modest to heavy work loads is probably a huge
mistake.
> > To expect that they will scale well under Linux with heavy loads is
> > almost certainly folly.
>
> this depends on the type of loads.  i do number crunching and have a
> quad ppro-200 (512k cache) machine.  the jobs are trivially
> parallelizable (i need to run many to build up stats, i can run
> multiple copies of the same job with differing random number seeds)
> and involve little or no disk activity.  the quad box really does give
> four times the performance of my older single ppro-200 (256k cache).
> with four jobs active i have 399% user cpu loading.  since i am never
> in the kernel for much, i didn't seem much improvement going from
> 2.0.x to 2.2.x (once the shopping deadlock problem in 2.0.34 and lower
> got fixed - 2.0.34 and below could only handle two cpus).
>
> --
> johan kullstam
>


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