InsideAMX Tertiary

CPU usage – taking the system’s pulse

One for the techo’s:  if you are experiencing occasional or frequent AMX misbehaviour requiring a reboot to clear, a good first place to look is CPU usage.  A typical AMX program should be using 10% or less of the CPU’s time.  A really complex one could be using 50% or so, but never 90% or more (after initial startup).

If you see CPU usage sitting at 99%, you most likely have a code problem!   The code it doing something it shouldn’t be and it's time to call the programmer of the system to investigate!!

How to check CPU usage:  open a telnet session to the Netlinx/DVX/DGX master and type ‘cpu usage’.  It will report three values – instantaneous, average over last 30 seconds and the maximum or peak usage.  If any of these are high (90% or higher) alarm bells should be ringing.  The screenshot below shows 4 readings taken approx. 10 seconds apart.  The instantaneous and peak (max) values aren’t that important, but it’s the 30sec average that’s meaningful.

NB – CPU usage just after a reboot will be high.  It’s best to wait a few minutes for all the start-up processes to finish their tasks.

Note also that high CPU usage by itself is not an absolute test of system health, nor will it tell you what is wrong.  It is just an indicator that something could be wrong.