Re: [Gems-users] L2 cache miss actions

[Konstantinos Nikas <knikas@xxxxxxxxxxxxxxxxx>]

Hi Mike,

thanks for the suggestion. I managed to record the information I wanted 
but now I am stuck at another point :-) .
What I want to do is make Ruby call a specific method (which is going to 
look into the L2 cache and do some tricks) every 1 million cycles. 
However I am not sure how I am supposed to do that, since (if I have 
understood it correctly) Ruby does not simulate every single cycle, but 
instead wakes up whenever there is an event from the processor.
Any suggestions?

Kind regards,

Kostis
> Just add a field to the Entry structure (defined in L2cache.sm) and
> then update the field with L2cacheMemory[addr].thread_ID :=
> in_msg.Requestor or similar
>
> --Mike
>
>
> On Thu, Jun 26, 2008 at 9:26 AM, Konstantinos Nikas
> <knikas@xxxxxxxxxxxxxxxxx> wrote:
>   
> > Hi all,
> >
> > I want to use Gems to study cache replacement policies for CMPs. One of
> > the things I need to do is add to the L2 cache a thread_ID field which
> > will hold the id of the processor/thread that brought the cache block
> > into the L2 cache in the first place.
> >
> > So, I have added an array that holds the id to the CacheMemory class and
> > whenever deallocate is called I reset the thread_ID of the touched block
> > (this is the easy part of course :-) ).  The problem is that I am not
> > sure how to set the ID whenever a new block is allocated into the cache.
> >
> > First of all, I am not sure what happens when a L2 miss is detected. I
> > would assume that the following happens :
> >
> > L2 miss detected -> L2_cacheMemory.cacheProbe (to find the replacement
> > victim) -> L2_cacheMemory.deallocate (deallocate the selected victim) ->
> > L2)_cacheMemory.allocate (allocation of the new block).
> >
> > Is that right? And more importantly where is this sequence defined?
> >
> > I 've looked at the generated code of the protocol and I found that in
> > L2Cache_Transitions.C the qq_allocateL2CacheBlock method (which calls
> > the allocate method of CacheMemory) is called when for example the state
> > in L2 is NP (not present) and the event is L2Cache_Event_L1_GET_INSTR.
> > However I wasn't able to find where the victim cache block was selected
> > and deallocated prior to the new block's allocation.
> >
> > Any pointers/comments/insights will be greatly appreciated!
> >
> > Kind regards,
> >
> > Kostis
> >
> >
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> >
> >
> >     
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>   

--
Dr. Konstantinos Nikas
Computing Systems Laboratory
School of Electrical and Computer Engineering
National Technical University of Athens

Tel: +30-210-7722495
e-mail: knikas@xxxxxxxxxxxxxxxxx
http://www.cslab.ece.ntua.gr/~knikas