Sample LLC miss references?

[Harald Servat <harald.servat@bsc.es>]

Dear list,

   I'd like to use PEBS to sample only misses at LLC on my Intel(R) 
Core(TM) i7-2760QM CPU.

   I've been digging into section 18.4.4 of the Intel® 64 and IA-32 
Architectures Developer's Manual: Vol. 3B and I've found that 
MEM_LOAD_RETIRED does not include LLC_MISSES in that event. However, in 
Table 19-13 (Section 19.6) the LLC_MISSES can be reported by setting 
umask 0x10. Since I'm interested on this particular counter, I guess 
that I cannot use perf mem command and I've have to stick with perf, am 
I right?

   In order to test this, I've modified the stream benchmark so that the 
accesses are random in each of the four kernels (copy, scale, add and 
triad) in order to reduce the spatial&temporal localities.

   So if I run

   # Capture MEM_LOAD_RETIRED.L2_HIT
   perf record -c 1 -e r02cb ./stream.rand

   The number of captured samples is about 2M.

   However, if I run

   # Capture MEM_LOAD_RETIRED.L3_MISS
   perf record -c 1 -e r10cb ./stream.rand

   then I get 0 samples. Is that a demonstration that it's impossible to 
capture precise misses at L3? If so, is there any alternative to do 
that? Could I use the latency to bring the data from the memory 
hierarchy instead?

Thank you very much, and happy new year!

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