The broker at present will log warnings about overrunning timer tasks and late wakeups. In general they can be ignored. The information in the warnings is only of interest if they are experiencing other problems that may be connected to the precision of timer tasks. The most obvious issue - for which I believe these warnings were introduced - is where clients are timing out due to delays to broker heartbeats.
Demoting the warnings to informational statements would avoid undue alarm and prevent excess noise in log files. Should there be a need to see the information it is a lot easier to enable it (--log-enable info+:TimerWarnings) than it is to turn it off at present.