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perf_event_open.2 Add PERF_IOC_FLAG_GROUP documentation 

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 man page.

Signed-off-by: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Vince Weaver 2013-06-28 16:55:12 -04:00 committed by Michael Kerrisk
parent 58c7d0c279
commit 8cc8b90de8
1 changed files with 19 additions and 5 deletions
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24
man2/perf_event_open.2
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@ -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