There's a workaround required for some events on Sandy bridge Xeon hardware. http://software.intel.com/en-us/articles/performance-monitoring-on-intel-xeon-processor-e5-family Here's the workaround packaged up in a linux-specific python script. ugh. https://github.com/andikleen/pmu-tools/blob/master/latego.py I have no idea about the specifics of the workaround; only that we should likely add support to hwpmc to do this.
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