Overflow in measuring energy

[Sonal Aggarwal]

Hello,

I am trying to measure the energy consumed by a particular program by varying the input sizes. I used both likwid-perfctr and likwid-powermeter to do that as they can query the RAPL counters. What I observed was that for large input sizes the energy went down tremendously which was really unexpected. My guess is that there is a limit upto which the msr register can hold values after which it is overflowed. Can you please suggest a workaround for this please.

Thanks

[Sonal Aggarwal]

I am using the SandyBridge processors with 2 Sockets and 8 cores each.

[Thomas Röhl]

Hi Sonal,

I wrote a comment to https://groups.google.com/forum/#!topic/likwid-developers/WUUPzkIKIlY which will answer most of your question.

As a workaround you could use the Marker API with regions that require only a small amount of time to reduce the overflow effect. If you want to measure your whole application there is currently no possibility to do it reliably with LIKWID.

Greetings,
Thomas