On Wed, May 15, 2013 at 11:27:02AM -0400, Steven Rostedt wrote: > > Coming into the middle of the thread is always hard, but why/how does perf > > disable nohz_full? I didn't think the hardware events of perf would cause > > problems as they are no different than an irq. Curious. > > Right now perf requires a tick, not sure exactly why, but you can look > at the code in perf_event_task_tick(). Thus if NO_HZ_FULL sees that a > perf tick is pending, it won't disable ticks. Unfortunately, the > watchdogs, both NMI and soft lockup, use the perf infrastructure to > trigger NMIs or interrupts. This adds a perf element on the rotate list > and keeps NO_HZ_FULL from *ever* activating.
Ok. Thanks. I don't know what the rotate list is for (nor what it does in general). But I'll poke around. Cheers, Don -- 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/
