This change clarifies the behavior of the PERF_FLAG_FD_OUTPUT and PERF_FLAG_FD_NO_GROUP flags to perf_event_open(), and removes the related FIXME comments. While writing tests to validate the behavior of these flags I discovered that PERF_FLAG_FD_OUTPUT has been broken since the 2.6.35 kernel release. Signed-off-by: Vince Weaver <vincent.weaver@xxxxxxxxx> diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2 index 8bde791..7181c29 100644 --- a/man2/perf_event_open.2 +++ b/man2/perf_event_open.2 @@ -149,14 +149,17 @@ then .BR execve (2). .TP .BR PERF_FLAG_FD_NO_GROUP -.\" FIXME . The following sentence is unclear -This flag allows creating an event as part of an event group but -having no group leader. -It is unclear why this is useful. -.\" FIXME . So, why is it useful? -.TP -.BR PERF_FLAG_FD_OUTPUT -This flag reroutes the output from an event to the group leader. +This flag tells the event to ignore the +.IR group_fd +parameter except for the purpose of setting up output redirection +using the +.B PERF_FLAG_FD_OUTPUT +flag. +.TP +.BR PERF_FLAG_FD_OUTPUT " (broken since Linux 2.6.35)." +This flag re-routes the event's sampled output to instead +be included in the mmap buffer of the event specified by +.IR group_fd . .TP .BR PERF_FLAG_PID_CGROUP " (since Linux 2.6.39)." This flag activates per-container system-wide monitoring. -- 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
