Re: [Gems-users] Relation between SIMICS cycle & GEMS cycle

["Weihang Jiang" <weihang.jiang@xxxxxxxxx>]

I used both.

On 3/29/06, Min Xu (Hsu) <xu@xxxxxxxxxxx> wrote:
> Did you use Opal or just Ruby only? It matters.
>
> On Wed, 29 Mar 2006 Weihang Jiang wrote :
> > Hi,
> >   Can anybody help me understand the relation between SIMICS
> > cycle and GEMS cycle.
> >
> >   SIMICS cycle means the number of cycles SIMICS thinks the
> > simulation has lasted, which can be calculated through
> > calling SIM_cycle_count() at the beginning and the end of
> > one simulation.
> >   GEMS cycle is referring to the number of cycles opal/ruby
> > has advanced.
> >
> >   Understanding the relation between SIMICS cycle and GEMS
> > cycle is important for utilizing system level profiling
> > tools. For example, vmstat reports both number of events
> > (e.g. bi, bo) and relative execution time (e.g. us,sy,id).
> > Other profiling tools report absolute execution time.
> >
> >   I did a small experiment to testify the relation. I ran
> > SIMICS+GEMS with two different cache configurations for
> > 10,000,000 GEMS cycles.
> >   In experiment 1, using fast cache, 407,808 instructions
> > have been executed and the SIMICS cycle number is 1,711,569.
> > In experiment 2, using slow cache, 401,245 have been
> > executed. However, the SIMICS cycle number is 1,664,671
> > (different from exp1).
> >
> >    Based on this experiment, my understanding is that,
> > SIMICS cycle is not an accurate measurement and those system
> > level profiling tools can not be used without care.
> >
> >    So, I have 2 questions:
> >
> > 1. Is my understanding correct?
> > 2. How much effort does it require to let SIMICS cycle have
> > more sense(i.e. let SIMICS cycle == GEMS cycle)?
> >
> >
> > --
> > Weihang Jiang,  UIUC
> >
> > _______________________________________________
> > Gems-users mailing list
> > Gems-users@xxxxxxxxxxx
> > https://lists.cs.wisc.edu/mailman/listinfo/gems-users
> _______________________________________________
> Gems-users mailing list
> Gems-users@xxxxxxxxxxx
> https://lists.cs.wisc.edu/mailman/listinfo/gems-users
>


--
Weihang Jiang