🚀 go-pugleaf

"Ilan Azbel" <ilan@mdio.net> wrote:
> I have a multi-threaded application running on a dual-CPU computer. Is
there
> any way to find out on which CPU a thread is running?

This question assumes that your thread will stay on the CPU once you ask.
This is not the case (by default):

int thread_func( )
    {
    /*  Pretend GetCurrentThreadCpuNumber() is an API
        that returns the current thread cpu number at
        the time the function was called. */
    int cpu_num = GetCurrentThreadCpuNumber( );

    /*  OOPS! The OS just preempted me and moved me to
        the other CPU, so the next line of output
        will be a flat-out lie! */
    std::cout
        << "I think I\'m running on cpu number "
        << cpu_num << std::endl;
    }

Note that you /can/ force your thread to run on a specific processor via
SetThreadAffinityMask or even suggest a processor to the OS via
SetThreadIdealProcessor.  But in both cases this is not likely to get you
any performance boost, because other threads can still run on that processor
and preempt your thread.


You might be able to get a tell which CPU your thread is running on by using
the CPUID assembly instruction, but it won't do you much good.

--
-- Early Ehlinger CEO, ResPower Inc - Toll-Free : 866-737-7697
-- www.respower.com -- 500+ GHz Supercomputer Starting At USD$0.50/GHz*Hour