Re: [PATCH 4/4 v2] watchdog: configure nmi watchdog period based onwatchdog_thresh

[Don Zickus]

On Wed, May 18, 2011 at 10:39:36AM +0200, Ingo Molnar wrote:
> 
> * Mandeep Singh Baines <msb@xxxxxxxxxxxx> wrote:
> 
> > Ingo Molnar (mingo@xxxxxxx) wrote:
> > > 
> > > * Mandeep Singh Baines <msb@xxxxxxxxxxxx> wrote:
> > > 
> > > > Before the conversion of the NMI watchdog to perf event, the watchdog
> > > > timeout was 5 seconds. Now it is 60 seconds. For my particular application,
> > > > netbooks, 5 seconds was a better timeout. With a short timeout, we
> > > > catch faults earlier and are able to send back a panic. With a 60 second
> > > > timeout, the user is unlikely to wait and will instead hit the power
> > > > button, causing us to lose the panic info.
> > > 
> > > That's an interesting observation. Have you been able to measure/observe this 
> > > effect somehow, or do you presume that users find 60 seconds too long?
> > > 
> > 
> > Mostly intuition. There is a threshold beyond which the user will hit
> > the power button. Not sure if its 20 seconds or 20 minutes. My feeling
> > was that the 1 minute was too long.
> > 
> > For a user experience perspective, a quick reboot also seems like a better
> > experience than a one minute hang. Our systems boot in 8 seconds and restore
> > the previous session so a reboot is almost not noticable.
> 
> Indeed you definitely want it configurable and have the delay down to 5 or 10 
> seconds, to correlate it with your boot delay.
> 
> Personally i consider any hang over 1 second annoying so you might want to work 
> on that 8 seconds boot time some more, it's too long ;-)
> 
> And any kernel code running with more than 1 second irqs off is a bug, plain 
> and simple.

Not necessarily, but in those cases the code can use touch_nmi_watchdog
(for example slow hardware, long print outs, etc). :-)

Cheers,
Don
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/