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perf tools: Update ioctl documentation for PERF_IOC_FLAG_GROUP

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The ioctl interface of perf event fd receives 3 arguments to control
event group behavior but it lacked documentation.

Signed-off-by: Namhyung Kim <namhyung.kim@lge.com>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1338443506-25009-2-git-send-email-namhyung.kim@lge.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Namhyung Kim 2012-05-31 14:51:45 +09:00 committed by Arnaldo Carvalho de Melo
parent aa5cdd308d
commit a59e64a13a
1 changed files with 4 additions and 3 deletions
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7
tools/perf/design.txt
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@ -409,14 +409,15 @@ Counters can be enabled and disabled in two ways: via ioctl and via
prctl. When a counter is disabled, it doesn't count or generate
events but does continue to exist and maintain its count value.
An individual counter or counter group can be enabled with
An individual counter can be enabled with
ioctl(fd, PERF_EVENT_IOC_ENABLE);
ioctl(fd, PERF_EVENT_IOC_ENABLE, 0);
or disabled with
ioctl(fd, PERF_EVENT_IOC_DISABLE);
ioctl(fd, PERF_EVENT_IOC_DISABLE, 0);
For a counter group, pass PERF_IOC_FLAG_GROUP as the third argument.
Enabling or disabling the leader of a group enables or disables the
whole group; that is, while the group leader is disabled, none of the
counters in the group will count. Enabling or disabling a member of a