On Wed, May 15, 2013 at 10:37:29AM +0200, Peter Zijlstra wrote: > On Tue, May 14, 2013 at 06:02:51PM +0200, Frederic Weisbecker wrote: > > From: Steven Rostedt <rost...@goodmis.org> > > > > Trying to test the nohz_full code, I was not able to get it to work. > > Finally I enabled the tick_stop tracepoint and it showed: > > > > tick_stop: success=no msg=perf events running > > > > I talked to Frederic Weisbecker about this and he informed me that > > perf is used by the lockup detector. I checked the code, and sure > > enough it is. > > > > As perf is always running when LOCKUP_DETECTOR is enabled, which > > will always disable nohz_full from working, instead of confusing > > users, disable LOCKUP_DETECTOR when NO_HZ_FULL is enabled. > > > > When perf is changed such that it does not prevent nohz_full from > > working, then we can and should remove this constraint. > > That's a bit contradictory in function, you want the NMI watchdog to > cover all code, so disabling whilst entering NO_HZ state is going to > make it not cover some code - *fail*. > > Rather I would suggest disabling the NMI watchdog's runtime default; so > you can still enable it with something like: > > echo 1 > /proc/sys/kernel/nmi_watchdog >
Sounds good, and we then warn the user about that. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
