presto-main/src/main/java/io/prestosql/execution/SplitConcurrencyController.java/SplitConcurrencyController/update
class SplitConcurrencyController:    public void update(long nanos, double utilization, int currentConcurrency)
    {
        checkArgument(nanos >= 0, "nanos is negative");
        checkArgument(isFinite(utilization), "utilization must be finite");
        checkArgument(utilization >= 0, "utilization is negative");
        checkArgument(currentConcurrency >= 0, "currentConcurrency is negative");

        threadNanosSinceLastAdjustment += nanos;
        if (threadNanosSinceLastAdjustment >= adjustmentIntervalNanos && utilization < TARGET_UTILIZATION && currentConcurrency >= targetConcurrency) {
            threadNanosSinceLastAdjustment = 0;
            targetConcurrency++;
        }
    }