presto-main/src/main/java/io/prestosql/event/QueryMonitor.java/QueryMonitor/populateDistribution
class QueryMonitor:    private static void populateDistribution(StageInfo stageInfo, ImmutableList.Builder<StageCpuDistribution> distributions)
    {
        distributions.add(computeCpuDistribution(stageInfo));
        for (StageInfo subStage : stageInfo.getSubStages()) {
            populateDistribution(subStage, distributions);
        }
    }