Your description of those 2 latencies makes sense. But there still has to
be latency for accessing the banks. How is this represented?
I greped "LATENCY" on MOESI_CMP_direcotry files, and I only see:
DIRECTORY_LATENCY,
MEMORY_LATENCY,
L2_RESPONSE_LATENCY,
L2_REQUEST_LATENCY,
L1_RESPONSE_LATENCY,
L1_REQUEST_LATENCY.
can anyone explain at a high level how this protocol works as far as
timing goes? I realize the network latency can be modelled by these
request and response latencies. But what is the latency of a load that
hits the local L2? I believe L1 latencies are 1 cycle since fasthit is
enabled.
thx,
Tom
On Thu, 12 Oct 2006, Greg Byrd wrote:
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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