Re: [Gems-users] how to modify the Last Recently Used timestamp of Cache Block

[Dan Gibson <degibson@xxxxxxxx>]

See my response, inlined below.

Regards,
Dan

On Tue, Mar 2, 2010 at 4:16 AM, shanshuchang <shanshuchang@xxxxxxxxx> wrote:

Hi all,

I have encountered problems in related to cache block’s Last Recently used timestamp.

According to a previous discussion: https://lists.cs.wisc.edu/archive/gems-users/2010-January/msg00058.shtml

it is said that Ruby's request is /not/ terminated on a squash, which may be caused by mis-prediction. That is, requests of false-path MEM insts would be serviced and the Last Recently Used timestamp of the cache block would be updated in case of such false-path MEM insts.

However, cache blocks related to the false-path MEM inst will be squashed later and, in my opinion, the timestamp of the cache blocks should not be updated.

You are proceeding on a false assumption. Neither cache blocks nor requests are ever squashed in Ruby. The memory system has no way to differentiate speculative accesses from non-speculative accesses at this time.

So I want to modify the update policy so that only those MEM insts that are to be retired update the timestamp of the cache blocks.

 

Any advices on how to do the modification?

 

Thanks in advance!

shuchang

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