paparazzi/conf/modules/sys_mon.xml

<!DOCTYPE module SYSTEM "module.dtd">

<module name="sys_mon" dir="core">
  <doc>
    <description>
System monitor.
The sys_mon module gives you some information about the timing of the periodic tasks and a rough estimate of cpu load (averaged over 1 sec).

The SYS_MON message contains the following information (all times are given in microseconds):
- @b periodic_time : time between two calls of the modules_periodic_task (averaged over 1s)
- @b periodic_time_min : minimum time between two calls of the modules_periodic_task() during the last second
- @b periodic_time_max : maximum time between two calls of the modules_periodic_task() during the last second
- @b periodic_cycle : time it took to execute the main periodic functions (averaged over 1s)
- @b periodic_cycle_min : minimum time it took to execute the main periodic functions during the last second
- @b periodic_cycle_max : maximum time it took to execute the main periodic functions during the last second
- @b event_number : number of times the event loop was called during the last second
- @b cpu_load : rough estimate of cpu load (averaged over 1 sec)


So your periodic_time should be 1/MODULES_FREQUENCY, which should be the same as 1/PERIODIC_FREQUENCY
The periodic_cycle_max should not be over the periodic_time, otherwise in at least one cycle it took longer to calculate everything and the next one was slightly delayed.


The sys_mon module has to run at the full main frequency!

So either don't specify a main_freq parameter for the modules node or set your actual main frequency
    </description>
  </doc>
  <header>
    <file name="sys_mon.h"/>
  </header>
  <init fun="init_sysmon()"/>
  <periodic fun="periodic_report_sysmon()" freq="1."/>
  <periodic fun="periodic_sysmon()"/>
  <event fun="event_sysmon()"/>
  <makefile target="ap">
    <file name="sys_mon.c"/>
  </makefile>
</module>