Re: UltraSPARC IV

From: Paul Drake <discgolfdba_at_yahoo.com>
Date: Sun, 6 Jun 2004 00:20:28 -0700 (PDT)
Message-ID: <20040606072028.90629.qmail@web20422.mail.yahoo.com>

Michael Thomas <mhthomas_at_yahoo.com> wrote:
> This can be amazing technology, especially in the
> wrong hands. ;-)

if you read the output of dmesg off of a linux box with a kernel that knows the difference between a physical and logical cpu, you'll see that the runqueue of logical is mapped to the physical. from just watching top, in a dual cpu system, the 2 physical CPUs will be loaded prior to any processes running on the logical(s). one can see overall cpu usage higher than 50% with hyperthreading enabled.

if the storage system is some form of RAID-F, the cpu wait % will be high enough that its not going to matter if you enabled or disabled hypterthreading anyways.

Mike - I'm sure that I'm not saying anything that you don't already know.

Paul

>
> --- Matthew Zito <mzito_at_gridapp.com> wrote:
> >
> ...
> > time, so its a little disingenuous to claim a
> > doubling of performance.
> >
> > Multi-core processing is different from Intel's
> > HyperThreading
> > technology - in that case, its a single processor
> > core that shows
> > itself as two processors. This is because Intel
> has
> > built a certain
> > amount of possible parallelization into their
> > processors already that
> > generally wasn't being taken advantage of by
> ...
>
> Its an easy trap to fall in. Running my first 3.2GHz
> CPU Hyperthreading PC I wondered why the individual
> processors were almost never running over 50%
> utilization. Must have a really powerful PC. Doh!
>
> Then I realized *if* the two Hyperthreading CPUs
> totaled over 100% it must be because of pipelining
> or
> parallelization of tasks. The only program I ever
> saw
> that made both Hyperthreading CPUs go to 100%
> simultaneously was SETI_at_Home. Obviously, it was
> programmed to *use* the technology.
>
> I can just see some 'well-meaning' SA (how tactful
> was
> that!) attempting to add more databases to one of
> these systems because "the CPUs are under utilized,
> and never go above XX percent". Could be
> entertaining... "My whole system is slow"... you
> know...
>
> Regards,
>
> Mike Thomas
>

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Received on Sun Jun 06 2004 - 02:17:30 CDT