Re: [Gems-users] LogTM Transactions Hanging (Gems 2.1)

[Jayaram Bobba <bobba@xxxxxxxxxxx>]

Thanks Javier for the clarification. I believe that instruction-fetch-mode
could influence the correctness of the simulation. Some conflict resolution
policies (like Timestamp) require the simulator to see every instruction 
fetch.
Typically, once a transaction is marked as 'to be aborted' by the 
conflict resolution policy,
the simulator generates a trap on the next memory request it receives 
from SIMICS. Now if
the next instruction happens to be COMMIT_TRANSACTION and SIMICS does not
report every instruction fetch then the transaction could be incorrectly 
committed.
So if you need to use instruction-cache-access-trace, then you should 
use it with a line
size equal to the instruction size.


Javier Merino wrote:
> Fuad Tabba wrote:
>   
> > > I am not sure what instruction-cache-access-trace is and how it differs
> > > from instruction-fetch-trace. The difference
> > > if any could also affect trap handling.
> > >       
> > Not really sure how why it is instruction-cache-access-trace as
> > opposed to instruction-fetch-trace. Is there a parameter I could
> > change?
> >
> >     
> From the serengeti reference manual:
> "If [instruction-fetch-mode is] set to instruction-cache-access-trace,
> the memory hierarchy will receive one (and only one) instruction fetch
> every time a new cache line is accessed. [...] If set to
> instruction-fetch-trace, all instruction fetches will be visible. Note
> that on x86 target, instruction-cache-trace-access is not available. On
> some other, instruction-fetch-trace is actually
> instruction-cache-trace-access with a line size equal to
> the instruction size (sparc-v9)."
>
> Simics warns you that instruction-fetch-mode is using
> instruction-cache-access-trace. It is ok, I don't think that's the
> source of your problem.
>
> Regards,
> Javier Merino
>
>   
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