Hi Vince, On 01/08/2015 06:04 PM, Vince Weaver wrote: > > 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. Patch applied. Thank you! > 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. Sigh! Cheers, Michael > 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. > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- 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
