Re: [Gems-users] Time spent in synchronization

[Dan Gibson <degibson@xxxxxxxx>]

gethrtime() is bogus under simulation. Solaris's view of time is 
horribly skewed under Simics alone or Simics+Ruby. Try measuring using 
RUBY_CYCLES instead.
Hemayet Hossain wrote:
> Hi All,
> I am simulating some splash2 benchmarks by using ruby with simics 2.2.19 
> (Solaris 10) and to characterize the time spent in synchronization, I 
> have instrumented the synchronization calls like locks and barrier. I 
> have binded each thread to a specific processor (one-to-one) and 
> collecting the time by calling high resolution timer gethrtime().  In 
> real machine run (having 16 processors) for 16 threads I get around 19% 
> time spent on synchronization for a program. If I run the same program 
> in simics without ruby, I also get similar percentage of time spent in 
> synchronization.
> But If I run the same program in simics with ruby, the time spent in 
> synchronization is much higher (goes around 75% of total).  I have 
> collected the time from both programs and from ruby. Both are getting 
> almost same percentage number. I am using MESI_SCMP_directory like 
> protocol having 2 cycles for L1 and 14 cycles for L2 access.
> Does anyone have any idea what's going on? What wrong with my setup? I 
> would really appreciate your reply.
> Thanks,
> Hemayet
>
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