The perf_event_open() ENABLE/DISABLE/RESET ioctls can take an argument, PERF_IOC_FLAG_GROUP. This wasn't documented at all until about a year ago (despite the support being there from the beginning) so I missed this when initially writing the manpage. Signed-off-by: Vince Weaver <vincent.weaver@xxxxxxxxx> diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2 index 5b8e769..5900b1c 100644 --- a/man2/perf_event_open.2 +++ b/man2/perf_event_open.2 @@ -1664,7 +1664,10 @@ file descriptors Enables the individual event or event group specified by the file descriptor argument. -The ioctl argument is ignored. +If the +.B PERF_IOC_FLAG_GROUP +bit is set in the ioctl argument then all events in a group are +enabled, even if the event specified is not the group leader. .TP .B PERF_EVENT_IOC_DISABLE Disables the individual counter or event group specified by the @@ -1677,7 +1680,10 @@ Enabling or disabling a member of a group other than the leader affects only that counter; disabling a non-leader stops that counter from counting but doesn't affect any other counter. -The ioctl argument is ignored. +If the +.B PERF_IOC_FLAG_GROUP +bit is set in the ioctl argument then all events in a group are +disabled, even if the event specified is not the group leader. .TP .B PERF_EVENT_IOC_REFRESH Non-inherited overflow counters can use this @@ -1702,10 +1708,18 @@ multiplexing or .I time_running values. -When sent to a group leader, only -the leader is reset (child events are not). -The ioctl argument is ignored. +If the +.B PERF_IOC_FLAG_GROUP +bit is set in the ioctl argument then all events in a group are +reset, even if the event specified is not the group leader. + +If the +.B PERF_IOC_FLAG_GROUP +bit is not set then the behavior is somwhat unexpected: +when sent to a group leader only the leader is reset +(children are left alone); +when sent to a child all events in a group are reset. .TP .B PERF_EVENT_IOC_PERIOD IOC_PERIOD is the command to update the period; it -- 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
