PF & SMP

["Miguel Figueiredo Mascarenhas Sousa Filipe" <miguel.filipe@xxxxxxxxx>]

Hi all,


On 9/22/06, Joerg Sonnenberger <joerg@xxxxxxxxxxxxxxxxx> wrote:
>  On Fri, Sep 22, 2006 at 09:38:31AM -0700, Matthew Dillon wrote:
> >     As part of my parallel buildworld test I record the contention
> >     count delta for each -j 8 build.  I typically get numbers in the
> >     800-900 million range.  x 100 ns pertick == about 100 seconds of wasted
> >     of cpu (for both cpus together) for a buildworld that takes 1450 seconds,
> >     and dividing by the two cpus, that probably represents a real-world
> >     loss in build time of between 4% and 7% over what it could hav achieved.
> >     That is a very rough estimate, I haven't actually measured what a 'tick'
> >     is... it could be less then 100ns but I don't think it is more.
>
> Hm. On my build machine: around 3e6/s during a parallel build...
>
> Joerg


I'm not shure I understood correctly the meaning of those number, and
their impact on actual smp speedup (or lack thereof)..

How does that correlate to speedup on a parallel build ?
for instance..  build -j8:
- in UP mode > 1450s
- in SMP mode >  825s (1450/2 + 100)?

sorry, I don't have a smp system to test out...

best regards




--
Miguel Sousa Filipe

--
Miguel Sousa Filipe