Re: [Gems-users] Opal simulation question

[Philip Garcia <pcgarcia@xxxxxxxx>]

I don't think GEMS 2.0 directly supports doing simulations for a set  
number of cycles (although I could be wrong).  I just modified opal to  
count cycles instead of instructions committed on CPU #0.  This can be  
done by changing a single line in opal/system/system.C.
In the simulate() method change the while (m_sim_status==SIMSTATUS_OK   
&& instrCount>=m_seq[0]->m_stat_committed[0]) loop to be just: while  
(m_sim_status==SIMSTATUS_OK  && instrCount>=m_global_cycles)
This will just use the instrCount variable to be compared to global  
cycles.  Personally I prefer using this metric, as the number of  
instructions executed on CPU #0 is kind of an arbitrary length of time  
(particularly when comparing different benchmarks), whereas a set  
number of cycles has at least a baseline involved.   It's difficult to  
say though which one is definitively a "better" measurement, I'm sure  
some people here have a better background in this to make a claim.   
Personally, I prefer the set # of cycles measurement, and especially  
can't really make sense of what a set number of instructions executed  
on cpu #0 means when running multiprocessor workloads.
Of course, when giving number of cache misses, and some of those  
statistics it might make more sense to first normalize them, because  
giving the number of cache misses for 2 different setups that compute  
a different amount of work isn't very meaningful.  I think a standard  
metric there is miss rate (percent of load/store instructions that  
cause a cache miss) or use something like misses per thousand  
instructions.
Phil
On Mar 26, 2009, at 5:06 PM, Berkin Ozisikyilmaz wrote:

> Is it possible to stop simulation with opal after a predetermined  
> number of
> cycles? I know that opal.sim-step takes the number of instructions to
> simulate. Also would it be fair comparison to compare performance/ 
> cache
> misses etc. statistics across simulations with the same number of  
> cycles?
> Thanks
> Berkin
>
>
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