Re: [Gems-users] Cache miss profiling


Date: Mon, 20 Nov 2006 18:54:16 -0500
From: Ranjith Subramanian <ranji@xxxxxxxxxxxxx>
Subject: Re: [Gems-users] Cache miss profiling
Thanks Dan.

I'm not sure what you mean by the L1s are not separate entities in all the protocols.

I notice that for the MOESI_CMP protocol, the L1Cache controller calls profile_miss(...) from the Ruby_Slicc interface which in turn calls addSecondaryStatSample(...) which increments the number of misses in the L2 cache. The L2Cache controller calls profile_L2Cache_miss(...) which in turn calls addSecondaryStatSample.

I'm not too clear on the difference in the details between the different protocols, but it seems odd that the L1 cache controller's profiling function eventually calls addSecondaryStatSample(...). This is not the case in the MOSI_SMP protocol though.

Ranjith

Dan Gibson wrote:

Many of the protocols do not actually profile the L1s.

In fact, the L1s are not separate entities in the all the protocols... so the point at which L1 accesses are profiled varies from protocol to protocol, if indeed they are profiled at all.

It should be relatively straightforward to add L1 profiling. If "fast path hits" are ON, (see rubyconfig.defaults), then you can add profiling code to Sequencer.C. Otherwise, you can use the L1 controller's SLICC code.

Regards,
Dan Gibson

Ranjith Subramanian wrote:
Hello,
I have a question about how cache misses are profiled in ruby. I start simics, load a checkpoint which is essentially the prompt after a linux boots up, load ruby and continue simulating for a few seconds and dump ruby stats. I see that the L1 instruction and data caches aren't accessed at all but the L2 cache is. All the misses reported for the L2 cache are demand misses. I'm not sure what I'm missing here.

Ranjith
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