Re: [Gems-users] Data prefetch in ruby

[Mike Marty <mikem@xxxxxxxxxxx>]

Yes, I think you are right.

Adding hardware prefetching has been done with GEMS.  We have a 
stride/stream prefetching module somewhere in our "attic" of code that 
directly injects prefetch request messages to L2 controllers (for L1->L2 
prefetching) and then there is also L2->memory prefetches. 

Those bits were probably leftover from this code and are not used.   I 
don't remember if the bits are set for software prefetches...I think 
they are.  Opal will also set these prefetch bits when it prefetches 
permissions for a block before the instruction can retire. 

--Mike


Niket wrote:
> Hi,
> In the ruby/generated/{protocol} folder there is a file PrefetchBit.{h, 
> C} which defines the different kinds of prefetch: PrefetchBit_No, 
> PrefetchBit_Yes, PrefetchBit_L1_HW, PrefetchBit_L2_HW. Also, the 
> Sequencer looks at the PrefetchBit of the request and does a bunch of 
> things. But, since this is being done by looking at a request, this is 
> for Software Prefetch.
> The PrefetchBit_L1_HW and the PrefetchBit_L2_HW are never used and just 
> defined. But my intuition is that hardware prefetching code can be 
> easily added  if you follow  the code of the software prefetch.
> Mike, am I right ?
>
> --Niket
>
> Mike Marty wrote:
>   
> > I don't believe we have released a hardware prefetching module with 
> > GEMS.  What files are you referring to?
> > --Mike
> >
> > Tushar Krishna (tkrishna@xxxxxxxxxxxxx) wrote:
> >   
> >     
> > > Hi,
> > > I am planning to experiment with data prefetching in ruby. I noticed that hardware prefetch is already present in it. Could anyone tell me which prefetch scheme is being used? And can the prefetch be enabled for CMPs as well?
> > >
> > > --Tushar
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