does there exist a way to calculate time spent on interrupts handling ?

Joel Sherrill joel.sherrill at
Fri Feb 11 13:55:48 UTC 2000

Kirill Korotaev wrote:
> Hi, everyone!
> I know there is CPU_usage_Dump() function to dump thread cpu usage. But can
> I
> easily dump interrupts cpu usage? I think this should be important for RTOS.

There is currently no generic RTEMS mechanism for accounting for time
in ISRs.  

In case you did not notice the CPU_usage report is based on noticing
which task is running when the clock ticks and as a direct result is 
only an approximation.  It is safe to assume that multiple tasks can
and often do execute between two consecutive clock ticks.  Did each
of those tasks take 0 clock ticks or 1 clock tick to execute?

There needs to be a higher granularity timestamp to make this completely
accurate and to account for time spent in ISRs.  

Adding this capability and defining the infrastructure required to
portably support this would be a nice thing. :)
> Kirill

Joel Sherrill, Ph.D.             Director of Research & Development
joel at                 On-Line Applications Research
Ask me about RTEMS: a free RTOS  Huntsville AL 35805
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