I am not getting enough samples

By default, the starting sample interval is every 20ms. You can change the sampling rate if you get warnings about too few samples on a fast run, or want more detail in the results.

Solution

To increase the interval to every 10ms, set environment variable FORGE_SAMPLER_INTERVAL=10.

Note

Sampling frequency automatically decreases over time to ensure a manageable amount of data is collected, and does not depend on the length of the run.

Linaro recommends that you avoid increasing the sampling frequency if there are lots of threads or very deep stacks in the target program. This might not leave sufficient time to complete one sample before the next sample is started.

Note

Whether OpenMP is enabled or disabled in Linaro MAP or Linaro Performance Reports, the final script or scheduler values set for OMP_NUM_THREADS is used to calculate the sampling interval per thread (FORGE_SAMPLER_INTERVAL_PER_THREAD). When configuring your job for submission, check whether your final submission script, scheduler or the Linaro MAP GUI has a default value for OMP_NUM_THREADS.

Note

Custom values for FORGE_SAMPLER_INTERVAL are overwritten by values set from the combination of FORGE_SAMPLER_INTERVAL_PER_THREAD and the expected number of threads (from OMP_NUM_THREADS).