presto-main/src/main/java/io/prestosql/operator/TaskContext.java/TaskContext/getFullGcTime
class TaskContext:    public Duration getFullGcTime()
    {
        long startFullGcTimeNanos = this.startFullGcTimeNanos.get();
        if (startFullGcTimeNanos < 0) {
            return new Duration(0, MILLISECONDS);
        }

        long endFullGcTimeNanos = this.endFullGcTimeNanos.get();
        if (endFullGcTimeNanos < 0) {
            endFullGcTimeNanos = gcMonitor.getMajorGcTime().roundTo(NANOSECONDS);
        }
        return new Duration(max(0, endFullGcTimeNanos - startFullGcTimeNanos), NANOSECONDS);
    }