Re: [Gems-users] LxCACHE_TRANSITIONS_PER_RUBY

[Mike Marty <mikem@xxxxxxxxxxx>]

Ruby currently doesn't really model port contention in cache banks.  It is 
possible to add this, but the default doesn't model it.
First, L1CACHE_TRANSITIONS_PER_RUBY_CYCLE is completely meaningless for 
the processor->cache ports because Ruby (usually) handles L1 hits without 
any transitions.  You can use it to restrict the number of snoops the 
cache is able to handle per cycle.  But only if the -cache.sm file does 
not use any zz_recycle* actions.
--Mike


> Hi, Mike.
> Thanks for your quick response.
> I would like to keep my question for details.
>
> // i.e. the number of ports to each controller
> // L1cache is the sum of the L1I and L1D cache ports
> For example, let's suppose that we have 2 ports(one input and one output) in
> L1 cache. Then, should I set L1CACHE_TRANSITIONS_PER_RUBY to 2?
> If it is the case, I think it might mean that mandatory queue will be search
> twice in a cycle, and generate two requests with different addresses
> individually at the same cycle.
> Could you check if I go wrong? Thank you.
>
>
> Regards,
>
> Young
>
>
>
>
>
> > Well it determines how many transitions the L1 Controller will process
> in a cycle.  For certain protocols, it can be used to approximate bank
> contention.  However for any protocol that uses recycle, it is pretty
> much meaningless and should probably be set to a high value.
>
> It is specifically used in L1Cache_Controller::wakeup() in the generated
> L1Cache_Wakeup.C file.
>
> --Mike
>
>
> Juyoung Jung wrote:
> > Dear Gems-Users,
> >
> >
> > Could anyone explain about what the variable
> > "L1CACHE_TRANSITIONS_PER_RUBY_CYCLE" in
> > ruby/config/rubyconfig.defaults means?
> > The comment in rubyconfig file says the below:
> >
> > // Number of transitions each controller state machines can complete
> > per cycle
> > // i.e. the number of ports to each controller
> > // L1cache is the sum of the L1I and L1D cache ports
> >
> > The default value is set to 32 for each type of machines such as L1,
> > L2, and Directory. Shoud I set the exact same number as the defined
> > ports for this variable?
> > I am worrying about this variable's role because I could ran
> > simulation without modifying this variable.
> > Thank you.
> >
> > Regards,
> >
> > Young