On Wed, 25 Jan 2012, Madhavan manivannan wrote:
Hi Nilay,
Thanks! I still have a few more questions based on what you said.
1. I checked cpu/simple/timing.cc again and it seems like cycles are only
accounted for Events (during the period when the context is available). If
the need is to measure the time spent inside the parallel regions, which
figure be more appropriate (rubycycles or m5.numCycles) considering that
This depends on what you are trying to do and what you think is the
correct metric.
the difference is not negligible? I would assume ruby and m5 to also have
progressed the same number of ticks (irrespective of events in the cpu or
cache), which when converted to cycles should give the same number. There
still seems to be a diffference which I find hard to reason about.
The time is kept using a global tick value, which is same for both the cpu
and the memory system.
2. The numInst stat variable in cpu/simple/base.hh seems to be incremented
using the countInst() function (assuming TimingSimpleCPU). Since this
function is called whenever an instruction completes execution and since it
does not work on the granularity of a microop, I am still doubtful about
What makes you think the function is not being called per microop? I think
you need to read the code again.
the missing accesses. I however have a similar question like before; In
case I want to count the number of instructions executed (Ifetch accesses)
which stat would be more appropriate?
3. I have made an attempt to rephrase the last question. I hope it is more
understandle now. Assuming there is no need for ruby and m5 to have
progressed the same number of cycles, why is there a difference between the
sum of cumulative latencies (this figure is obtained by adding the
latencies of all cache access requests that reach a specific sequencer) and
the number of rubycycles progressed. Is the difference because rubycycles
include the CPU latencies in addition to latencies from cache access
requests?
Yes.
--
Nilay
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