On Fri, Nov 15, 2013 at 4:08 PM, Vince Weaver <vi...@deater.net> wrote: > On Fri, 15 Nov 2013, Ingo Molnar wrote: >> >> Btw., does the kernel side currently support discovery of such >> impossible group scheduling constraints at group setup time? If not >> then it probably should and it should reject them straight away. > > It does not, or at least I'm pretty sure it can't if the NMI watchdog is > enabled (Stephane, are you doing your tests with NMI watchdog disabled?) > I think my tests were with watchdog disabled.
> This is a big problem with PAPI. If the NMI watchdog is enabled you can't > tell if a group will fail until the first read, the kernel can't tell you > at setup time. > Unless, you build the group and measure in for a short bit of time to validate runtime execution. But then there is no guarantee either. Because the perf_events situation may change, e.g., you may get another pinned event. So I don't think you will ever get that guarantee at setup time. I goes back to the core design idea behind perf_events. -- 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/
