Re: [Gems-users] state transitions in MOESI

["hongxia sun" <sunhx.seraph@xxxxxxxxx>]

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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