Re: [Gems-users] simulating perfect L2 for CMP


Date: Mon, 9 Oct 2006 12:26:40 -0700 (PDT)
From: Thomas Yeh <tomyeh@xxxxxxxxxxx>
Subject: Re: [Gems-users] simulating perfect L2 for CMP
Thx for the suggestion. I need the protocol to be simulated, so I'll have to run opal and ruby.
I assume that setting the memory latency to zero 
involves setting PERFECT_MEMORY_SYSTEM to true and 
PERFECT_MEMORY_SYSTEM_LATENCY to 0.
PERFECT_MEMORY_SYSTEM: false
PERFECT_MEMORY_SYSTEM_LATENCY: 0


On Mon, 9 Oct 2006, Dan Gibson wrote:

I recommend you set the memory latency to zero.

My other comments follow:

Thomas Yeh wrote:
I am currently simulating with the MOESI_CMP_directory protocol, and would
like to run the simulations with a perfect L2.

What is the best way to do this?
1) Running opal without ruby and specifing L2_IDEAL?

Running without ruby doesn't simulate any cache coherence. Unless this
is what you're intending, running without Ruby is probably a bad option.
2) Run both opal and ruby, but specify L2 is always a hit locally?

Yes, you could do that.
Is the L1 always 1 cycle when running opal w/o ruby? I don't see
a parameter for setting the L1 latency.

Opal w/o Ruby uses its own cache model, based on a uniprocessor
hierarchy. See Opal's cache.[Ch].
If I run without ruby, how do I compare the performance? Since there won't
be a ruby_cycle metric.

Opal will still produce several metrics. Pick your favourite and use
that instead.
thx,
Tom

Regards,
Dan

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