OFFCORE_RESPONSE_0:OTHER event on Ivy Bridge

BGoel · ‎09-02-2014

I am trying to understand the request type "OTHER" for OFFCORE_RESPONSE_x event (bit 15 of MSR_OFFCORE_RSP_x) on Ivy Bridge (Core i7-3770). Can someone tell me what kind of request types are counted by enabling this bit?

I have written a simple code that allocates a buffer, touches all the elements in the buffer once and then reads all the cachelines in the buffer in a loop:

  buf = (char*) malloc(range*CBSIZE);

  memset(buf,1,range*CBSIZE);

  for(counter = 0; counter < 10000; counter ++){
      for(i=0;i<range; i++)
        localbuf = localbuf + (int)buf[i * CBSIZE];
  }

For this piece of code, with buffer size = 64K less which is than L2 size (256 KB), I see almost no L2 Misses (<10K misses out of 10M loads), but the OFFCORE_RESPONSE_0:OTHER:LLC_HITM value is around 4M. The same experiment on Haswell microarchitecture (Core i7 4770) shows no count for OFFCORE_RESPONSE_0:OTHER:LLC_HITM. I am confused as to what is contributing to this event count on Ivy Bridge. Any help would be greatly appreciated.