[Gems-users] Performance evaluation of CMP with Ruby and Opal

["Lei Yang" <lya755@xxxxxxxxxxxxxxxxxxxx>]

Dear list,

 

I've been using GEMS to develop a new cache coherence protocol. I first used Ruby and Ruby Tester to verify its correctness. Thanks to the many advices from GEMS authors and users, the new protocol seems to have passed the tester. Now, I want to use the Opal processor model together with my modified Ruby module on Simics and run multiprogrammed SPEC benchmarks. I have a few questions to discuss with you.

 

1. The simulation is very very slow and it seems impossible to run the entire benchmark. 10 million cycles cost me more than one hour. Although I can specify warm up length, it is best to cover the entire life span of the benchmark. Has anyone tried to use a sampling approach? I guess it's OK to wait on the completion of the entire benchmark when producing final performance numbers, but it certainly is a pain whenever there is modification to the code and we want to see how it affects the performance. GEMS users, how do you handle this problem?

 

2. Exactly what performance number should I look at to compare two systems, when both Opal and Ruby are used. I saw on FAQ that one should use Ruby_cycles  to measure the runtime of the simulated system. But when I let Opal run the same number of cycles, shouldn't Ruby_cycles be the same for both? If not, why?

 

I appreciate your comments!

 

Thanks,

Lei