Re: [Gems-users] What kind of state will be if the data is in IGS/IGM state and receives an INV message from dir?

["Mike Marty" <mike.marty@xxxxxxxxx>]

If I recall correctly, the IGM state means that the first-level directory has issued a request to the second-level directory.  But since the second-level request has not yet been ordered at the second-level directory, it is still possible to receive invalidation request ( an L2 S state transitions to IGM when the first-level directory sees a GETX).  The first-level directory just acknowledges the invalidate, but stays in IGM/IGS because eventually its request will be handled.  If you set IGM/IGS to I, then the protocol will not work.

--Mike

On Thu, Jul 10, 2008 at 11:19 PM, wei wang <apollo.mobility@xxxxxxxxx> wrote:

i spotted the following state transitions related to handling an INV message in MOESI_CMP_directory

transition({IGM, IGS}, Inv)
transition({I,NP}, Inv)
transition(S, Inv, I)

all the transitions will send an ACK message to global directory, which is simply ignored in the directory. While
I -> I, NP -> NP and S->I set the data in one of the stable state, IGM -> IGM and IGS ->IGS will leave data in a transient states. Is this right? should we set IGM and IGS to I as well? thanks.

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