Hey Nilay,
I just wanted to say another "good work"  to you in tackling this issue.  I
am looking forward to seeing an updated patch here. After the the ISCA
deadline, I'd like to lock in on this issue more and help where I can (It's
at least pretty important to my future work).

I've admittedly lost some touch on the specifics of this thread, but I
would agree with you on that it's probably the best path to get the simpler
version to work (at the head of the store buffer) first since that would be
a subset of the more complicated version anyway (cases where it's not at
the head of the store buffer).

Right?

On Mon, Nov 14, 2011 at 5:27 PM, Nilay Vaish <[email protected]> wrote:

> On Fri, 11 Nov 2011, Nilay Vaish wrote:
>
>  I am thinking of implementing a modified version Brad's second proposal.
>> Each store accesses the cache at most twice. Once, when the store is
>> committed, following cases can happen --
>> * store is at the head of the store buffer, then issue write req to
>> memory system
>> * store is not at the head of the store buffer. If architecture has TSO
>> as memory model, then issue a read exclusive request to the memory system.
>> Else if a relaxed model is in place, a write request is sent to the memory
>> system.
>>
>> Once the store reaches the head of the store buffer, the actual store is
>> issued in case of TSO. Even if the store buffer receives an invalidation
>> for some address to which a store exists in the buffer, the read ex request
>> would not be issued again.
>>
>>
> Before starting the implementation for this scheme, I had implemented the
> scheme in which only the store at the head of the store queue is allowed to
> be in flight.
>
> For past two-three days, I have been trying to write the code for the
> scheme described above. As of now, it seems to me that I am writing this
> code by trying to debug the error I observe when running the simulation.
> Given the complexity of the code, adding this feature would only complicate
> the code further. And given that we want TSO and Alpha's memory model to
> co-exist, it seems to me that we will be making this code lot more complex
> than it is today.
>
> My opinion is that we should go with the simple implementation, rather
> than going for the aggressive approach and complicating the code further.
>
>
> --
> Nilay
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>



-- 
- Korey
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