371
System Performance Analysis (SPA) Software
System Performance Analysis Software
Next, you go to the State Histogram menu and enter the names and
boundaries of the five routines in the state histogram ranges.
State Histogram then displays the relative activity of the five routines.
After several acquisitions, it is apparent that the interrupt routine is
being accessed more often than expected.
The figure below shows the State Histogram display for this example.
SPA State Histogram
You now go to the Time Interval menu and enter the Start and End
conditions for the suspect interrupt routine. Before altering the default
Time Interval ranges, you start the acquisition and observe the
Maximum (Max), Minimum (Min), and Average (Avg) times. From
these values, the typical execution times of the interrupt are apparent,
and provide good starting values for the Time Interval ranges using
Auto-range. From the Max time, it is apparent that the interrupt
routine is having problems.