presto-main/src/main/java/io/prestosql/execution/SqlQueryManager.java/SqlQueryManager/start
class SqlQueryManager:    @PostConstruct
    public void start()
    {
        queryTracker.start();
        queryManagementExecutor.scheduleWithFixedDelay(() -> {
            try {
                enforceMemoryLimits();
            }
            catch (Throwable e) {
                log.error(e, "Error enforcing memory limits");
            }

            try {
                enforceCpuLimits();
            }
            catch (Throwable e) {
                log.error(e, "Error enforcing query CPU time limits");
            }
        }, 1, 1, TimeUnit.SECONDS);
    }