Software Tuning, Performance Optimization & Platform Monitoring
Discussion regarding monitoring and software tuning methodologies, Performance Monitoring Unit (PMU) of Intel microprocessors, and platform updating.

PMC 0xD1 and LFB hit count



    I am using retired LD hit status, PMC 0xD1, but I've yet in real applications and in tests been unable to get any non-zero count for LD uop hits to the LFB.  This would be PMC 0xD1 and unit mask 0x40.  I'm comparing the count, for the sum of PMC 0xD1 with LFB hits, L1D hits and L1D misses, which should equal that of the number of retired LD uops (PMC 0xD0 unit mask 0x81).  These 2 do not equal one another once there are misses to the L1D.  I think what's missing is the count of the # of hits a LD uop upon a LFB previously allocated by another request or hw pref.

    Could you tell me whether:

   * sw pref and "demand", real uops associated with code - not hw pref, are counted by PMC 0xD1.

      * I believe SW pref is qualified by these PMCs as a LD uop, please verify.

Thank you in advance for any notice as to whether the LFB count works in HW.. or info as to what this counter is counting (it's not HW pref.. right).



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