gem5 simulation time is high
Question: good day every body  
  
I have a real problem here that took a near of couple weeks on searching but
without a conclusion  
  
I'm trying to run a compiled c++ code (a binary file) on gem5 to measure the
time consumed for some architectures I made using python and make my compare
to show the statistics etc..  
  
this would look OK using binaries that take a small amount of time to finish
but when a binary should take let's say 2 seconds for example, the simulation
time would be really big  
how to resolve this issue, I need simulation time optimized as possible  
I think it would be easy but I'm not able to figure it out until now :\  
  
what I reached until now is:  
\- building gem5 in fast mode, but that did not give me any difference from
the optimized mode in the simulation time  
\- using the fast forwarding in the optimized mode, however. I could not get
that done until now  
  
any help please !


Answer: A few suggestions:

  * You can use Classical Memory model if the program does not involve complex memory interactions. This would be faster than the Ruby model.
  * Fast forward your application upto the point where the real computation begins. You mentioned it did not work for you. One thing to check would be : if you're using Ruby memory model, that doesn't support fast forwarding. It works with Classic memory model. <http://www.m5sim.org/General_Memory_System>
  * Another thing that might be of interest to you is Simpoints, which can characterize the important sections of your app so that you run those instead of the complete app. Of course, you might want to run the complete app later, but this can give you a decent first order comparison across architectures. Check <http://gem5.org/Simpoints>

