linux-kernel - Re: [PATCH 2/3] perf tools: Update ioctl documentation for PERF_IOC_FLAG

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Date:	Thu, 31 May 2012 11:35:54 -0300
From:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
To:	Namhyung Kim <namhyung.kim@....com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...hat.com>,
	Namhyung Kim <namhyung@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] perf tools: Update ioctl documentation for
 PERF_IOC_FLAG_GROUP

Em Thu, May 31, 2012 at 02:51:45PM +0900, Namhyung Kim escreveu:
> The ioctl interface of perf event fd receives 3 arguments
> to control event group behavior but it lacked documentation.

But the argument is not used for ENABLE or DISABLE, so why require it?

- Arnaldo
 
> Signed-off-by: Namhyung Kim <namhyung.kim@....com>
> ---
>  tools/perf/design.txt |    7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/design.txt b/tools/perf/design.txt
> index bd0bb1b1279b..67e5d0cace85 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
> -- 
> 1.7.10.2
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