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How to calculate the CPU load when an OS is used? - Knowledgebase / OS-aware debugging - Lauterbach Support

How to calculate the CPU load when an OS is used?

The CPU load can be computed based on trace information, i.e. off-chip or on-chip trace is needed in this case.

First, you need to set up OS-aware debugging by loading the OS awareness or ORTI file. Please refer to the TRACE32 manual of the used target operating system (e.g. rtos_freertos.pdf for FreeRTOS or rtos_orti.pdf for AUTOSAR CP) for more information.

Example 1: Load ORTI file for AUTOSAR CP

TASK.ORTI < my_orti_file >

Example 2: Load awareness for FreeRTOS on Arm

TASK.CONFIG ~~/demo/arm/kernel/freertos/freertos.t32

Then, task switches need to be recorded in the trace. Please refer to TRACE32 manual of your target OS for more information.

Example: enable flow trace and task switches recording in the trace based on data trace:

Break.Set TASK.CONFIG(magic) /TraceData

The CPU load can then be computed as the percentage of time the CPU wasn't in the idle loop. The command Trace.PROfileChart.TASK gives such a percentage view. You just have to identify the "idle" task(s).

1. Create a task group for this task with merge or hide option:  

GROUP.CreateTASK "idle" "<my_idle_task>" /MERGE



2. If the chart should not distinguish between the other tasks, you may also merge them:






If neither off-chip nor onchip trace is available, then the SNOOPer can be used to periodically sample the current task. Please note however that the results are in this case not accurate as when using off-chip or on-chip trace since they are based on periodically collected samples. The target processor needs additionally to support accessing the memory on run-time.


SNOOPer.SELect %Long TASK.CONFIG(magic)
WAIT 5.s


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