Re: [patch 8/8] Add abilty to enable/disable nmi watchdog from sysfs

[Andi Kleen]

> On Tue, May 09, 2006 at 04:50:43PM -0400, dzickus wrote:
> > 
> > Adds a new /proc/sys/kernel/nmi call that will enable/disable the nmi
> > watchdog.
> > 
> 
> This means you can at runtime enable/disbale nmi_watchdog, i.e., reserve
> some performance counters on the fly. This gets complicated because now
> the perfmon subsystem 

Right now we don't care about perfmon at all because it's not in (x86) mainline
If you want anybody to care you have to submit and pass review

> (and probably oprofile) cannot check register 
> availability when they are first initialized. Basically each time,
> the /sys entry is modified, they would have to scan the list of available
> performance counters. I don't know exactly when Oprofile does this checking.
> For perfmon, this is done only once, when the PMU description table is loaded.

I think the NMI watchdog will fail if the register is already allocated.
oprofile should check and allocate when it fills in the register. 

-Andi

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