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Re: PF & SMP

From: Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx>
Date: Sun, 24 Sep 2006 15:23:00 -0700 (PDT)

: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

    No, it's a bit more complex then that.  make -j builds do not run
    processes in parallel all the time, there are a number of places
    during the build where everything collapses into a single target
    or requirement.  There are also a number of places where the
    machine is I/O bound and SMP becomes irrelevant, and at least one
    place (during the compilation of GCC) where the machine can become
    memory bound.

					Matthew Dillon 

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