On Fri, May 09, 2014 at 09:10:50AM +0200, Ingo Molnar wrote: > > * Don Zickus <[email protected]> wrote: > > > On Thu, May 08, 2014 at 07:35:01PM +0200, Ingo Molnar wrote: > > > > > > * Don Zickus <[email protected]> wrote: > > > > > > > > > Again, I don't have a solution to juggle between PMI performance > > > > > > and reliable delivery. We could do away with the spinlocks and > > > > > > go back to single cpu delivery (like it used to be). Then > > > > > > devise a mechanism to switch delivery to another cpu upon > > > > > > hotplug. > > > > > > > > > > > > Thoughts? > > > > > > > > > > I'd say we should do a delayed timer that makes sure that all > > > > > possible handlers are polled after an NMI is triggered, but never > > > > > at a high rate. > > > > > > > > Hmm, I was thinking about it and wanted to avoid a poll as I hear > > > > complaints here and there about the nmi_watchdog constantly wasting > > > > power cycles with its polling. > > > > > > But the polling would only happen if there's NMI traffic, so that's > > > fine. So as long as polling stops some time after the last PMI use, > > > it's a good solution. > > > > So you are thinking an NMI comes in, kicks off a delayed timer for > > say 10ms. The timer fires, rechecks the NMI for missed events and > > then stops? If another NMI happens before the timer fires, just kick > > the timer again? > > > > Something like that? > > Yeah, exactly, using delayed IRQ work for that or so. > > This would allow us to 'optimistic' processing of NMI events: the > first handler that manages to do any work causes a return. No need to > make a per handler distinction, etc. > > It would generally be pretty robust and would possibly be a natural > workaround for 'stuck PMU' type of bugs as well.
Agreed. I'll try to hack something up for that. > > [ As long as it does not result in spurious 'dazed and confused' > messages :-) ] Hehe. Cheers, Don -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
