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Question below:


src/mem/protocol/MESI_Two_Level-L1cache.sm (line 1227)
<http://reviews.gem5.org/r/2842/#comment5532>

    Why introduce a new action here?  It seems like the simplier way to handle 
this situation is insert the forward_eviction_to_cpu action after the 
hx_load_hit callback rather than introduce a new action and additional 
complexity in the sequencer.


- Brad Beckmann


On May 21, 2015, 7:27 p.m., Marco Elver wrote:
> 
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> http://reviews.gem5.org/r/2842/
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> 
> (Updated May 21, 2015, 7:27 p.m.)
> 
> 
> Review request for Default.
> 
> 
> Repository: gem5
> 
> 
> Description
> -------
> 
> Changeset 10839:2978f9ed5e7a
> ---------------------------
> ruby: Add ReadRespWithInvalidate support, fixes MESI consistency bug
> 
> A sunk Inv in the IS state needs to be propagated to the LQ eventually. Thus 
> far, Ruby has no support for properly propagating an invalidate along with a 
> ReadResp.
> 
> This patch adds support for ReadRespWithInvalidate upon a readCallback, so 
> that the LQ can properly deal with such a request.
> 
> Note that we cannot just do a forward_eviction in the IS,Inv transition, as 
> other outstanding loads in the LQ after the one for which we get the Inv, may 
> be satisfied (with old values) inbetween the Inv and IS_I,Data transitions.
> 
> The scenarios are the same as for the problem fixed in revision 10575 (which 
> addressed the LSQ side of things).
> 
> 
> Diffs
> -----
> 
>   src/mem/protocol/MESI_Two_Level-L1cache.sm ecbab2522757 
>   src/mem/protocol/RubySlicc_Types.sm ecbab2522757 
>   src/mem/ruby/system/Sequencer.hh ecbab2522757 
>   src/mem/ruby/system/Sequencer.cc ecbab2522757 
> 
> Diff: http://reviews.gem5.org/r/2842/diff/
> 
> 
> Testing
> -------
> 
> Tester no longer finds bug. Note this was done with an (older) version of 
> gem5 that was still happy with Ruby+O3CPU. A quick run with ruby-tester 
> yielded no obvious issues.
> 
> 
> *NOTE:* I'm not entirely happy with the "Hack?" code. If someone can possibly 
> suggest how we can add a nicer way to add support for ReadRespWithInvalidate 
> to Ruby, then that'd probably be better than what this patch does.
> 
> 
> Thanks,
> 
> Marco Elver
> 
>

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