Re: [Gems-users] changing cache latency


Date: Thu, 12 Oct 2006 15:05:37 -0400
From: Greg Byrd <gbyrd@xxxxxxxx>
Subject: Re: [Gems-users] changing cache latency
Thomas Yeh wrote:
I see that L2_REQUEST_LATENCY and L2_RESPONSE_LATENCY are used.

When I change the size of each bank that's placed locally with each core, I would like to change the latency of accessing each bank.

Which parameter should I change?

I think that these parameters only deal with the delay inside the L2 controller itself. When an event occurs that causes a request message to be sent out, there is a delay of L2_REQUEST_LATENCY between the event and when the request message is enqueued. Likewise for a response message and L2_RESPONSE_LATENCY.

My guess is that all of your banks are actually the same, and that the latency difference will be the amount of time that it takes to reach a bank from a particular core. If that's the case, then that latency should be reflected in the interconnection network, not in the L2 module itself.
Also, I see a directory cache latency in the ruby stats file. It defaults to 80. Is the directory assumed to be in memory?

Yes.

...Greg

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