Good day to you.
I notice that some cells are grey in the bottom-up window which read: This metric cannot be reliably calculated due to multiplexing issues or a low number of collected PMU samples.
I want to know if I can get this result from the command-line interface. There are lines in the hotspots report that are unreliable which I can, but some are not so obvious. It would be a waste of time to check manually one by one using the GUI interface. What's the threshold of a low number of collected PMU samples?
The online documentation for this issue is available at https://www.intel.com/content/www/us/en/develop/documentation/vtune-help/top/troubleshooting/wrong-e... and https://www.intel.com/content/www/us/en/develop/documentation/vtune-help/top/analyze-performance/hw-...
Basically, the number of PMU hardware events VTune data collectors can monitor during a single run is limited by the processor, so VTune can "multiplex" the collection of multiple counters. The workaround when you experience this issue is to allow multiple runs (-allow-multiple-runs command line argument and "Allow multiple runs" GUI checkbox in the What -> Advanced pane).
To see the threshold for each event, in the GUI, expand the Details view in the How pane and scroll down to the "Events configured for CPU: ..." section where the events and "Sample After" values are listed. The sample after values are the counts that are triggering this message.