Re: x86's nmi_hz wrt. oprofile's nmi_timer_int.c

[Andi Kleen <andi@firstfloor.org>]

David Miller <davem@davemloft.net> writes:

Really old mail, but I was very behind. I didn't see an 
correct answer, so let's answer it.

> While working on an NMI watchdog implementation on sparc64
> I noticed what seems to be a peculiar behavior of the NMI
> timer int oprofile support on x86.
>
> When the NMI watchdog tests itself at boot timer we start
> with nmi_hz equal to HZ.
>
> After the NMI watchdog self-test passes, nmi_hz is reduced
> down to '1'.
>
> The NMI timer int oprofile support simply uses DIE_NMI notifiers for
> it's implementation.  But I don't see anything in the code of
> arch/x86/oprofile/nmi_timer_int.c nor the NMI watchdog infrastructure
> which will re-adjust nmi_hz back to HZ or something similar.
>
> Am I missing something?

oprofile generates its own NMIs, it does not rely on 
the ones from the nmi watchdog.

In timer mode it does not use nmis or die notifiers, but relies on the 
regular non nmi timer interrupt.

Does that answer your question?

-Andi
-- 
ak@linux.intel.com -- Speaking for myself only.