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Subject[tip:perf/urgent] perf tools: Update ioctl documentation for PERF_IOC_FLAG_GROUP
Commit-ID:  a59e64a13a927fb7530bef39e9f5e7de8268137e
Gitweb: http://git.kernel.org/tip/a59e64a13a927fb7530bef39e9f5e7de8268137e
Author: Namhyung Kim <namhyung.kim@lge.com>
AuthorDate: Thu, 31 May 2012 14:51:45 +0900
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Thu, 31 May 2012 11:38:42 -0300

perf tools: Update ioctl documentation for PERF_IOC_FLAG_GROUP

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>
---
tools/perf/design.txt | 7 ++++---
1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/tools/perf/design.txt b/tools/perf/design.txt
index bd0bb1b..67e5d0c 100644
--- a/tools/perf/design.txt
+++ b/tools/perf/design.txt
@@ -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

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