On Wed, Nov 02, 2011 at 01:09:46PM +0200, Gleb Natapov wrote: > > > > The user can cause this to be very small (even zero). Can this cause an > > > > NMI storm? > > > > > > > If user will set it to zero then attr.sample_period will always be 0 and > > > perf will think that the event is non sampling and will use max_period > > > instead. For a small value greater than zero how is it different from > > > userspace creating an event with sample_period of 1? > > > > I don't know. Does the kernel survive it? > > > Need to test, but I do not see anything in the kernel that prevent userspace > from setting it to any value. > You can set sample_period to 1 by providing -c 1 to perf top/record. Kernel survives it easily since perf subsystem kindly throttles interrupts for you. You can set max interrupt per event per time tick in /proc/sys/kernel/perf_event_max_sample_rate. -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
