linux-kernel - Re: perf_counter: hook up the tracepoint events

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Date:	Wed, 29 Jul 2009 04:59:54 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC:	mingo@...hat.com, hpa@...or.com, tglx@...utronix.de, mingo@...e.hu,
	paulus@...ba.org, linux-kernel@...r.kernel.org,
	rostedt@...dmis.org, linux-tip-commits@...r.kernel.org
Subject: Re: perf_counter: hook up the tracepoint events

Peter Zijlstra wrote:
> On Tue, 2009-07-28 at 21:01 -0400, Jeff Garzik wrote:
>> Peter Zijlstra wrote:
>>> diff --git a/init/Kconfig b/init/Kconfig
>>> index 8a38443..761129a 100644
>>> --- a/init/Kconfig
>>> +++ b/init/Kconfig
>>> @@ -945,6 +945,11 @@ config PERF_COUNTERS
>>>  
>>>  	  Say Y if unsure.
>>>  
>>> +config EVENT_PROFILE
>>> +	bool "Tracepoint profile sources"
>>> +	depends on PERF_COUNTERS && EVENT_TRACER
>>> +	default y
>>> +
>>>  endmenu
>> Adding help text would be... helpful.   :)
>>
>> The net result in this case was the addition of a completely-unexplained 
>> Kconfig option late in 2.6.31-rc.
>>
>> Maybe the x86 maintainers could help see that they don't push 
>> unexplained Kconfig options upstream -- particularly ones we are asked 
>> to enable by default?
> 
> You're right. Johannes Berg made the same complaint yesterday.
> 
> Is the below any good?
> 
> ---
> Subject: perf_counter: Add help text to CONFIG_EVENT_PROFILE
> 
> Explain what tracepoint profile sources is about.
> 
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> ---
>  init/Kconfig |    6 ++++++
>  1 files changed, 6 insertions(+), 0 deletions(-)
> 
> diff --git a/init/Kconfig b/init/Kconfig
> index 13473ac..ffae67c 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -957,6 +957,12 @@ config EVENT_PROFILE
>  	bool "Tracepoint profile sources"
>  	depends on PERF_COUNTERS && EVENT_TRACING
>  	default y
> +	help
> +	 Allow the use of tracepoints as software performance counters.
> +
> +	 When this is enabled, you can create perf counters based on
> +	 tracepoints using PERF_TYPE_TRACEPOINT and the tracepoint ID
> +	 found in debugfs://tracing/events/*/*/id.

Thanks.  Is this feature useful w/out debugfs?

If yes, ACK.

	Jeff




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