Cache-references and Cache-misses counters

Cache-references and Cache-misses counters

Imagen de odedh

I hope this is an appropriate place to post my question.

Using the linux /proc/mtrr i have configured all physical memory space to be uncachable.
I have then ran 'perf stat myapp' and looked on the cache counters for references and misses.

Since i have used mtrr to set all physical memory as uncachable, i was expecting the
cache misses to be 0 (zero), as uncachable memory should not be referencing the cache to begin with..

When running on an old Core E6700 CPU, I got both cache-references, as well as cache-misses to be 0.
When running on a newer X3430 Xeon CPU, I got both cache-reference and cache-misses to be the same number
(as all memory references where also cache-misses)

Is there any expected behvious when it comes to counter references to uncachable memory?
In praticular memory that was configured uncachable by mtrr?

Regards,
Oded

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Imagen de Konstantin Lupach (Intel)

AFAIK, the only right way to measure these and other Intel microarchitecture related things is to use EBS (event-based sampling)feature in Intel profilers. We cannot guarantee anylevel ofquality for doing this withOS general mechanisms.
If you decide to try one of Intel profilers supporting EBS you can address questions to a forum dedicated to profiler of your choice.

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