[LITMUS^RT] cache effect on rtspin -- Sisu

[Sisu Xi]

Hi, Glenn and Björn:

Thanks for your reply. Yes, I understand that rtspin is only used for
synthetic workload and should only be used for testing scheduler behavior.
 :)

Sisu


On Fri, Apr 19, 2013 at 11:07 AM, Björn Brandenburg <bbb at mpi-sws.org> wrote:

>
> On Apr 19, 2013, at 5:42 PM, Glenn Elliott <gelliott at cs.unc.edu> wrote:
>
> >
> > On Apr 19, 2013, at 11:31 AM, Sisu Xi <xisisu at gmail.com> wrote:
> >
> >> Hi, all:
> >>
> >> I was looking at the code of rtspin, does cache miss make a difference
> in rtspin?
> >>
> >> Because rtspin run workload, record time, compare it with wcet and
> rerun some workload, the cache miss time should already be considered in
> the execution time.
> >>
> >> In other words, consider one rtspi with alwasy cache hit and the other
> rtspin with alwasy cache miss. If they are configured the same wcet, each
> job should run for same time.
> >>
> >> Is this correct?
> >>
> >> Thanks very much!
> >>
> >> Sisu
> >>
> >> --
> >> Sisu Xi, PhD Candidate
> >>
> >> http://www.cse.wustl.edu/~xis/
> >> Department of Computer Science and Engineering
> >> Campus Box 1045
> >> Washington University in St. Louis
> >> One Brookings Drive
> >> St. Louis, MO 63130
> >> _______________________________________________
> >> litmus-dev mailing list
> >> litmus-dev at lists.litmus-rt.org
> >> https://lists.litmus-rt.org/listinfo/litmus-dev
> >
> >
> > Hi Sisu,
> >
> > I believe that you are correct.  If you want to make it cache-sensitive,
> you would need to rewrite job() to execute a fixed number of operations on
> data of an appropriate size.  You would provision the execution time of the
> task however you need (average case, worst-case, average case with no cache
> misses, worst-case with no cache misses, etc.---it's up to you).
> >
> > Check out litmus-rt/tools/perf for tools for counting cache misses,
> branch mispredictions, etc.
>
> Just to add some more context: rtspin is primarily a testing tool. It
> allows you to try out whether the scheduler does what you expect it to do.
> It's useful for generating pretty schedules. It is not primarily a
> performance testing tool. It is certainly not reflective of cache-related
> execution cost variations in any real workload.
>
> - Björn
>
>
> _______________________________________________
> litmus-dev mailing list
> litmus-dev at lists.litmus-rt.org
> https://lists.litmus-rt.org/listinfo/litmus-dev
>



-- 
Sisu Xi, PhD Candidate

http://www.cse.wustl.edu/~xis/
Department of Computer Science and Engineering
Campus Box 1045
Washington University in St. Louis
One Brookings Drive
St. Louis, MO 63130
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