[Gems-users] Barrnes CPI question

["KS Chow" <g0706256@xxxxxxxxxx>]

I have a question regarding the CPI I got from a ruby dump file.

I am comparing the CPI between 2 simulations: a single core machine and a dual-core – all the necessary configurations done in Simics and Ruby (not using Opal).

For the 1-core I ran Barnes with the param indicating 1 processor; the dual-core is run with the param indicating 2 processors.

 

1-core CPI = 3.27789

2-core CPI = 0.621735

 

Is it normal to have such a huge drop in CPI going from 1 to 2 cores? Both have 16Mbs L2 cache and equal amount of L1.

I also noticed that in the 1-core 10,974,780 instructions were executed vs 194,051,043 in the 2-core – why such a big difference in num instructions executed?

Is this caused by the num processors param in Barnes?

 

Thanks/Regards.

 

Chow Kian Sim

National University of Singapore