The PERF_EVENT_IOC_PERIOD ioctl was broken until 2.6.36, and it turns out that the ARM architecture has some differing behavior too. Reported-by: Andreas Sandberg <andreas.sandberg@xxxxxxxx> Signed-off-by: Vince Weaver <vincent.weaver@xxxxxxxxx> diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2 index f4cb5bd..f337a27 100644 --- a/man2/perf_event_open.2 +++ b/man2/perf_event_open.2 @@ -1976,11 +1976,17 @@ reset, even if the event specified is not the group leader (but see BUGS). .TP .B PERF_EVENT_IOC_PERIOD -IOC_PERIOD is the command to update the period; it -does not update the current period but instead defers until next. +This updates the overflow period for the event. +On most architectures the new period does not take effect until +after the next overflow happens; +on ARM since Linux 3.7 the period is updated immediately. The argument is a pointer to a 64-bit value containing the desired new period. + +Prior to Linux 2.6.36 this ioctl always failed due to a bug +in the kernel. + .TP .B PERF_EVENT_IOC_SET_OUTPUT This tells the kernel to report event notifications to the specified -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
