[ltt-dev] Problem in irq handling

Philby John pjohn at in.mvista.com
Fri Jun 5 11:54:14 EDT 2009

On Fri, 2009-06-05 at 20:48 +0530, Kiran Kulkarni wrote:
> Hello,
> I am using LTTng for my device which has arm processor. I have stuck at 
> a problem that after each timer interrupt
> my cpu spends 10ms time in serving irq (Graph representation also shows 
> same). So it actually spends time 10 ms for each timer interrupt,
> which I guess not correct. (Note: My timer interrupt update system timer 
> by 10ms).
> can you help me figure out what causing irq handlers to take 10ms....

The entry and exit in your ISR calculates to a value in nanoseconds. So
the total time to execute the ISR is 0.009ns even though the system
timer ticks every 10ms.

This is how I see it, I could be wrong though.

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