[Gems-users] cache statistics

["Mladen Nikitovic" <mladen@xxxxxxxxxxx>]

Hi,

I need some clarification to understand the statistics generated by
ruby_dump_stats. I'm especially interested in cache-specific statistics. If
I understand it correctly, there's a profiler that collects data about
number of misses in the cache. However, the total number of cache requests
is not visible here. There are entries, "Data requests" and "Insn requests",
that are available under "Simics Driver Transaction Stats". 

Should I interpret these two entries as the total number of L1D and L1I
requests respectively?

My impression was that there is one L1 cache per processor, but when looking
at the ruby code or statistics I see no evidence of that. Was my expectation
wrong? I'm using the MOSI_SMP_bcast protocol.

Under "Chip Stats" there are "event counts" for L1 cache. But, if I sum up
the number of Load, Ifetch, and Store, I do not get the same number as the
"Data requests" and "Insn requests" from "Simics Driver Transaction Stats."

Would also like to get number of L2 accesses, but that should correspond to
L1I and L1D misses specified in the Profiler stats section, right?

My goal is to collect statistics for each L1 cache. I have followed the
methods called from the operate function in ruby.c
(mh_memorytracer_possible_cache_miss, SimicsDriver::makeRequest,
SimicsDriver::recordTransactionStats) and tried to see where the different
stat counters are incremented. However, I don't see a "natural" place in the
code I could add my own code to distinguish between different L1 caches.
Could you enlighten me into this matter?

Best Regards,
Mladen