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Re: time stamp counter in "make check"


On Fri, Jul 13, 2012 at 5:59 AM, Dmitrieva Liubov
<liubov.dmitrieva@gmail.com> wrote:
> But I don't know how to implement this feature in a good way.
> Maybe it should be just option for make check to use correct time
> stamp counter instead of counter with misleading results.
> I guess some people can be interesting just in stability testing not
> performance.
> But ... replacing rdtsc with rdtscp for core i7 increases "make check"
> execution time in more than 2 times.
>
> On my machine time of "make check" running in 4 threads is as following:
>
> Before replacing:
>
> -bash-4.2$ time nohup make check -j4
> nohup: ignoring input and appending output to `nohup.out'
>
> real    6m41.962s
> user    5m18.994s
> sys     2m9.086s
>
> After replacing:
>
> real    20m56.105s
> user    13m7.373s
> sys     7m9.821s
>
> I guess some people may be disappointed if the change will be not optional.
>
> I didn't check how CPUID barrier effects time, but likely even greater
> than rdtscp/rdtscp replacing fix.
>

Please use CPUID as barrier for rdtsc,  rdrscp can only be used if
processor support it.

Thanks.


-- 
H.J.


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