Re: [Gems-users] MOESI_CMP_directory protocol : Invalid Transition

[Mike Marty <mikem@xxxxxxxxxxx>]

Oops.  The transition needs to be broken down further to get rid of the
duplicate.

Instead of adding ILOX to the same transition, undo that change and add
this as a new transition:

transition(ILOX, {L1_PUTS, L1_PUTS_only}) {
  ll_writebackNack;
  o_popL1RequestQueue;
}


> Hi
>
> I incorporated your suggested fix - and got a compile
> error.
>
> ../protocols/MOESI_CMP_directory-L2cache.sm:1945:
> Warning: Duplicate transition: ILOX|L1_PUTO
>
> ../protocols/MOESI_CMP_directory-L2cache.sm:2253:
> Error: Duplicate transition: ILOX|L1_PUTO
>
> The ILOX transistion you suggested seems to contradict
> the following
>
> transition(ILOX, L1_PUTO, ILOXW) {
>     l_writebackAckNeedData;
>     o_popL1RequestQueue;
>   }
>
> Thanks
> Brinda
>
> --- Mike Marty <mikem@xxxxxxxxxxx> wrote:
>
> > Hi,
> >
> > I think the L2 controller needs to NACK in this
> > scenario.  This particular
> > path must have never occurred when I
> > developed/debugged the protocol.
> > These L1-L2 writeback races, with forwarded
> > requests, are nasty.
> >
> > Please try adding OLSX to the transition on line
> > 1485 of
> > MOESI_CMP_directory-L2cache.sm
> >
> >   transition({I, M, O, ILS, ILOX, OLS, SLS, OLSX,
> > S}, L1_PUTX) {
> >     ll_writebackNack;
> >     o_popL1RequestQueue;
> >   }
> >
> >
> > Same thing for the L1_PUTS in state ILOX.  Change
> > line 1942 to as follows:
> >
> >   // new exclusive happened while sharer attempted
> > writeback
> >   transition({ILX, ILOX}, {L1_PUTS, L1_PUTS_only,
> > L1_PUTO}) {
> >     ll_writebackNack;
> >     o_popL1RequestQueue;
> >   }
> >
> >
> >
> >
> > --Mike
> >
> >
> >
> >
> > > Hi
> > >
> > > I modified the MOESI_CMP_directory protocol to
> > > incorporate my dram simulator - but did nto add
> > nay
> > > additional states. I was using the tester to test
> > that
> > > I did not have any invalid transitions/deadlocks
> > due
> > > to my modifications and came across an event that
> > the
> > > original protocol did not handle.
> > >
> > > The combinations is the event L1_PUTX arriving
> > when
> > > the state of the block in the L2 Cache Controller
> > is
> > > OLSX.
> > >
> > > Thanks
> > > Brinda
> > >
> > >
> > >
> > >
> > >
> >
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