Re: [Gems-users] Comparing "ruby cycles" when running ruby alone and opal+ruby

[Dan Gibson <degibson@xxxxxxxx>]

Hi Alessandro,
Let me address each of your questions independently:

Alessandro Bardine wrote:

> Hi,
> I am trying to compare the ruby cycles value that I get
> when I run a benchmark in opal+ruby environment ( with DNUCA cache
> architecture) with the same value that I get when I only run ruby (with the
> same DNUCA cache) driven directly by Simics.
> My idea is to make a comparison for the "ruby cycles" values I get at some
> fixed number of executed instruction in both environments.
> To do this I step opal+ruby with the "sim-step" command and I collect the
> ruby cicle value at regular interval, while for ruby alone I collect info
> from the file generated with the "periodical-stat-file". 
>
> What I expected was to get similar results but what I am getting from the
> first simulations is quite different!!
>  
I would expect the value of ruby_cycles to vary greatly between 
Ruby-only and Opal+Ruby configurations. When Opal is NOT loaded, the 
processor model is that of an in-order, blocking machine. Opal simulates 
an out-of-order machine, and thus should behave very differently from 
(and probably perform better than) the Ruby-only configuration.
> Are the values of "ruby-cycles" for the two environments (intended at the
> same number of total executed instruction) directly comparable?
>  
The two values will show the performance of an in-order core for 
Ruby-only, and the performance of an out-of-order core for Opal+Ruby. 
They both are a measure of "execution time".
> For the "ruby alone" I get the number of executed instruction in the  file
> generated with the "periodical-stat-file", what is hard to understand for me
> is how ruby is able to know this value assumed that it is being driven by
> Simics.
>
>  
Ruby is aware of the number of instructions executed through the Simics 
API. That is, it is possible to simply ask Simics how many instructions 
have been executed on a given processor. See the Simics documentation 
(specifically, the Simics reference manual) for more information.
Regards,
Dan Gibson

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