Re: [PATCH][RFC] oprofile for 2.5.39

[Andi Kleen <ak@suse.de>]

> 
> Basically it's a matter of :
> 
> 	task_struct *
> 	EIP/Event
> 	EIP/Event
> 	EIP/Event
> 	EIP/Event
> 	....

I think you can easily do that by keeping state per cpu in the 
NMI handler.

	if (current == __get_cpu_var(oprofile_cpustate)) { 
		/* log current */
		__get_cpu_var(oprofile_cpustate) = current; 	
	} else { 
		/* do nothing */ 
	}
	/* log EIP */

[or when you are an module use an cache line padded array indexed with
smp_processor_id - per cpu data doesn't work from modules]

This is even more efficient because when the NMI rate is lower than
the task switch frequency (which is not unlikely) then you'll avoid
many useless task_struct loggings.

-Andi