On 12/24/2013 08:28 AM, Andi Kleen wrote:
On Tue, Dec 24, 2013 at 08:10:10AM +0100, Manuel Selva wrote:
"You cannot use uncore events to sample IPs" means that the values
corresponding to PERF_SAMPLE_IP are not correct ? Some benchmarks I
did by sampling ME_INST_RETIRED with PERF_SAMPLE_IP let me think
that I was able to get the source of th event. The IP value was
coherent. Maybe this is not always the case.
It's the IP of a random core on the socket that happens to read the uncore
registers.
Ok. Where should I have read this information, in the Intel Software
Developer’s Manual volume 3B (I guess this is a hardware limitation) ?
I checked what can be measured with the offcore facility. I can ask to
count remote memory accesses, but now I am not sure PEBS is enable for
these events. If the answer is no, I can't accurately identify remote
memory accesses with offcore events ? As a consequence I am wondering if
there is a way to do such thing ?
Manu
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