[Gems-users] Understand the protocol trace

["Lei Yang" <lya755@xxxxxxxxxxxxxxxxxxxx>]

Dear list,

 

I was experimenting with MSI_MOSI_CMP_directory protocol with the tester.  With the little.trace on GEMS online documentation http://www.cs.wisc.edu/gems/doc/wiki/moin.cgi/How_do_I_understand_a_Protocol , below is the protocol trace I got:

 

Testing clear stats...Done.
Reading trace from file 'little.trace'...
      1   7  -1        Seq               Begin       >       [0x400, line 0x400]
      4   1   3    L1Cache                Load     NP>L1_IS  [0x400, line 0x400]
    141   1   0    L2Cache             L1_GETS  L2_NP>L2_IS  [0x400, line 0x400]
    390   0   0  Directory                GETS     NP>S      [0x400, line 0x400]
    635   1   0    L2Cache      Data_ext_ack_0  L2_IS>L2_SS  [0x400, line 0x400]
   1097   7  -1        Seq                Done       >       [0x400, line 0x400] 1096 cycles NULL Yes
   1097   1   3    L1Cache             L1_Data  L1_IS>L1_S   [0x400, line 0x400]
   1101   1  -1        Seq               Begin       >       [0x400, line 0x400]
   1104   0   1    L1Cache                Load     NP>L1_IS  [0x400, line 0x400]
   1139   0   0    L2Cache             L1_GETS  L2_NP>L2_IS  [0x400, line 0x400]
   1176   0   0  Directory                GETS      S>S      [0x400, line 0x400]
   1309   0   0    L2Cache      Data_ext_ack_0  L2_IS>L2_SS  [0x400, line 0x400]
   1445   1  -1        Seq                Done       >       [0x400, line 0x400] 344 cycles NULL Yes
   1445   0   1    L1Cache             L1_Data  L1_IS>L1_S   [0x400, line 0x400]

According to the documentation, the first column indicates the cycle. I don't understand why the operation cycles are so large. In my configuration,

 

MEMORY_RESPONSE_LATENCY_MINUS_2: 78

DIRECTORY_LATENCY: 80

L2_RESPONSE_LATENCY: 6
L1_RESPONSE_LATENCY: 3
L1_REQUEST_LATENCY: 2
L2_REQUEST_LATENCY: 4
NETWORK_LINK_LATENCY: 40

I don't understand why the cache operations would add up to, 1096 cycles for the first LD as an example. Could someone explain this please? By the way, in the ruby config file, there is a TIMER_LATENCY: 10000. I wonder what this is.

 

Thanks a lot! I appreciate your comments.

 

Lei