Re: [PerfSuite-users] libpshwpc; working around implicit variables?

[Rick K. <rk...@nc...>]

Tirath,

> Thanks for clarifying that for me; for some reason I had the idea  
> that the interrupt is triggered every \tau seconds, at which point it  
> samples the counter, then resets it, then goes back to sleep for  
> another \tau seconds, repeat... in which case the total count in the  
> end should have been the aggregate count.

Well, that's not a bad idea but it's not the way it's implemented in 
PerfSuite.  I should say this is a limitation of PerfSuite, not the 
hardware or driver support - there's nothing to prevent one from 
configuring on, say, the Itanium2, one performance counter to generate
an interrupt after some number of events (whether cycles or whatever),
and use that as a trigger to read event counts from one of the other 3
counters on that CPU.  This could provide some type of real-time 
monitoring I think.

There will be a new example program available that does something similar 
but using interval timers (setitimer) to generate periodic interrupts, 
allowing the interrupt handler to read the current value of the counters.  
I'm thinking this is similar to what you're describing.

Rick