If some data in the cache is in S state, then the store event should send UPGRADE rather than GETX to the owner.
2007/4/10, Dave Z. <zhu_dave@xxxxxxxxx>:
Other than store events in S state, store events in O state trigger GETX events as well. I would say the
idea is to invalidate the other copies, but when a GETX request is received, the local copy is sent to the requestor. So, I still don't undertand why it's an exclusive data request rather than an invalidation
message?
Thanks,
Dave
--- "Datta, Kushal" <kdatta@xxxxxxxx> wrote:
> > Well, since the data is in the O State in P0, most
> probably it is updating the data (P0->store). > So, although P1 has the data in S state in its > cache, > it does not have the most-recent value. So P1 needs > to get the data from P0. >
> Thanks and regards, > Kushal. > Graduate Student, > Department of ECE, > UNC Charlotte. > > > > -----Original Message----- > From:
gems-users-bounces@xxxxxxxxxxx on behalf of > Dave Z. > Sent: Mon 4/9/2007 1:29 PM > To: Gems Users > Subject: Re: [Gems-users] state transitions in MOESI > > Hello, > > Let me correct my question. If some data is in S
> state > in the cache, on a store event: GETX event is sent > to > the owner directory. The directory then sends the > data > to the requesting cache. Why is it necessary to > acquire the data when the cache already has it in S
> state? > > Thank you, > > Dave > > > --- "Dave Z." <zhu_dave@xxxxxxxxx> wrote: > > > Hello, > >
> > I have a question regarding the state transitions > in > > MOESI-hammer (perhaps the same scenario exists in > > other protocols as well). Let's say we have two > > processors: P0 and P1 that share some data. P0 is
> > the owner, so the data is in O state in P0 and in > S > > state in P1. If P1 tries to write to the data, > GETX > > will be issued. P0 sees the Other_GETX event and > > sends the data back to P1, right? If so, why is
> > there a need to send the data even though P1 has > the > > data in S state? > > > > Thank you, > > > > Dave > > > > > > > >
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