On Thu, 23 Apr 2015 22:21:11 +0200 (CEST) Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote: > > Is the NMI code generic enough now to know that an NMI triggered, and > > we could detect that and ignore the latencies if one did. Or perhaps > > even add a tracepoint in the start and end of an NMI, to account for > > it, (add hooks there), in case there's any SMIs that sneak in after an > > NMI. > > There are tracepoints in nmi_enter() and nmi_exit() at least in the > kernel source I'm looking at. Ah, the "trace_hardirq_enter()". That would be something I could hook into, as the only thing that could trigger that when interrupts are disabled happen to be NMIs. > > > I guess I could also add an NMI notifier to let me know. But I know how > > much everyone loves notifiers :-) > > I was tempted to tell you to shoot yourself, but realized in time > that this would be politically incorrect. And I would have to go all CodeOfConflict on you. > > > > > > > Aside of that isn't there a way to detect SMI crap with performance > > > counters on recent hardware? > > > > > > > Nothing I know of that is generic enough. And just because an SMI > > triggers, doesn't mean it's bad if it is quick enough. We have had > > arguments with HW vendors about their SMIs, and used the hwlat_detector > > to show that their SMIs are not as innocent as they claim. But we also > > have seen SMIs trigger under 1us, where it doesn't affect the system. > > I know of a SMI event counter which is available on newer CPUs and > Intel promised to add a SMI cycle counter as well. I have no idea > whether that one ever materialized. PeterZ should know. Hmm, a cycle counter would be good to add. > > But at least on the machines which have the event counter it would be > usefull to include that information as well. I'll try to add onto this series to include SMI counters if they exist. Thanks, -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
