[PATCH] perf_counters: start documenting HAVE_PERF_COUNTERS requirements

[PATCH] perf_counters: start documenting HAVE_PERF_COUNTERS requirements

[Mike Frysinger]

Help out arch porters who want to support perf counters by listing some
basic requirements.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
---
i imagine more details would be good, but this is a starting point and
better than nothing

 init/Kconfig          |    2 ++
 tools/perf/design.txt |   15 +++++++++++++++
 2 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index c649657..20f85b1 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -936,6 +936,8 @@ config AIO
 
 config HAVE_PERF_COUNTERS
 	bool
+	help
+	  See end of tools/perf/design.txt
 
 menu "Performance Counters"
 
diff --git a/tools/perf/design.txt b/tools/perf/design.txt
index 860e116..f71e0d2 100644
--- a/tools/perf/design.txt
+++ b/tools/perf/design.txt
@@ -440,3 +440,18 @@ by this process or by another, and doesn't affect any counters that
 this process has created on other processes.  It only enables or
 disables the group leaders, not any other members in the groups.
 
+
+Arch requirements
+-----------------
+
+If your architecture does not have hardware performance metrics, you can
+still use the generic software counters based on hrtimers for sampling.
+
+So to start with, in order to add HAVE_PERF_COUNTERS to your Kconfig, you
+will need at least this:
+	- asm/perf_counter.h - a basic stub will suffice at first
+	- support for atomic64 types (and associated helper functions)
+	- set_perf_counter_pending() implemented
+
+If your architecture does have hardware capabilities, you can override the
+weak stub hw_perf_counter_init() to register hardware counters.
-- 
1.6.3.1

Re: [PATCH] perf_counters: start documenting HAVE_PERF_COUNTERS requirements

[Randy Dunlap]

Mike Frysinger wrote:
> Help out arch porters who want to support perf counters by listing some
> basic requirements.
> 
> Signed-off-by: Mike Frysinger <vapier@gentoo.org>
> ---
> i imagine more details would be good, but this is a starting point and
> better than nothing
> 
>  init/Kconfig          |    2 ++
>  tools/perf/design.txt |   15 +++++++++++++++
>  2 files changed, 17 insertions(+), 0 deletions(-)
> 
> diff --git a/init/Kconfig b/init/Kconfig
> index c649657..20f85b1 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -936,6 +936,8 @@ config AIO
>  
>  config HAVE_PERF_COUNTERS
>  	bool
> +	help
> +	  See end of tools/perf/design.txt

How about
	  See "Arch requirements" in tools/perf/design.txt
since it doesn't need to be at the end of the file forever.

>  
>  menu "Performance Counters"
>  
> diff --git a/tools/perf/design.txt b/tools/perf/design.txt
> index 860e116..f71e0d2 100644
> --- a/tools/perf/design.txt
> +++ b/tools/perf/design.txt
> @@ -440,3 +440,18 @@ by this process or by another, and doesn't affect any counters that
>  this process has created on other processes.  It only enables or
>  disables the group leaders, not any other members in the groups.
>  
> +
> +Arch requirements
> +-----------------
> +
> +If your architecture does not have hardware performance metrics, you can
> +still use the generic software counters based on hrtimers for sampling.
> +
> +So to start with, in order to add HAVE_PERF_COUNTERS to your Kconfig, you
> +will need at least this:
> +	- asm/perf_counter.h - a basic stub will suffice at first
> +	- support for atomic64 types (and associated helper functions)
> +	- set_perf_counter_pending() implemented
> +
> +If your architecture does have hardware capabilities, you can override the
> +weak stub hw_perf_counter_init() to register hardware counters.


-- 
~Randy
LPC 2009, Sept. 23-25, Portland, Oregon
http://linuxplumbersconf.org/2009/

[PATCH] perf_counters: start documenting HAVE_PERF_COUNTERS requirements

[Mike Frysinger]

Help out arch porters who want to support perf counters by listing some
basic requirements.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
---
 init/Kconfig          |    2 ++
 tools/perf/design.txt |   15 +++++++++++++++
 2 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index c649657..ee2e3c2 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -936,6 +936,8 @@ config AIO
 
 config HAVE_PERF_COUNTERS
 	bool
+	help
+	  See "Arch requirements" in tools/perf/design.txt
 
 menu "Performance Counters"
 
diff --git a/tools/perf/design.txt b/tools/perf/design.txt
index 860e116..f71e0d2 100644
--- a/tools/perf/design.txt
+++ b/tools/perf/design.txt
@@ -440,3 +440,18 @@ by this process or by another, and doesn't affect any counters that
 this process has created on other processes.  It only enables or
 disables the group leaders, not any other members in the groups.
 
+
+Arch requirements
+-----------------
+
+If your architecture does not have hardware performance metrics, you can
+still use the generic software counters based on hrtimers for sampling.
+
+So to start with, in order to add HAVE_PERF_COUNTERS to your Kconfig, you
+will need at least this:
+	- asm/perf_counter.h - a basic stub will suffice at first
+	- support for atomic64 types (and associated helper functions)
+	- set_perf_counter_pending() implemented
+
+If your architecture does have hardware capabilities, you can override the
+weak stub hw_perf_counter_init() to register hardware counters.
-- 
1.6.3.1

Re: [PATCH] perf_counters: start documenting HAVE_PERF_COUNTERS requirements

[Paul Mundt]

On Fri, Jun 12, 2009 at 01:27:12PM -0400, Mike Frysinger wrote:
> diff --git a/tools/perf/design.txt b/tools/perf/design.txt
> index 860e116..f71e0d2 100644
> --- a/tools/perf/design.txt
> +++ b/tools/perf/design.txt
> @@ -440,3 +440,18 @@ by this process or by another, and doesn't affect any counters that
>  this process has created on other processes.  It only enables or
>  disables the group leaders, not any other members in the groups.
>  
> +
> +Arch requirements
> +-----------------
> +
> +If your architecture does not have hardware performance metrics, you can
> +still use the generic software counters based on hrtimers for sampling.
> +
> +So to start with, in order to add HAVE_PERF_COUNTERS to your Kconfig, you
> +will need at least this:
> +	- asm/perf_counter.h - a basic stub will suffice at first
> +	- support for atomic64 types (and associated helper functions)
> +	- set_perf_counter_pending() implemented
> +
> +If your architecture does have hardware capabilities, you can override the
> +weak stub hw_perf_counter_init() to register hardware counters.

It would be nice to see this in arch/Kconfig instead, as that tends to
provide a centralized checklist for new features, especially when they
are non-trivial. At least I found the arch/Kconfig bits very helpful for
things like tracehook support, without having to grovel around
Documentation for verbose design documents that I otherwise couldn't care
less about.

Re: [PATCH] perf_counters: start documenting HAVE_PERF_COUNTERS requirements

[Mike Frysinger]

On Sun, Jun 14, 2009 at 05:41, Paul Mundt wrote:
> On Fri, Jun 12, 2009 at 01:27:12PM -0400, Mike Frysinger wrote:
>> diff --git a/tools/perf/design.txt b/tools/perf/design.txt
>> index 860e116..f71e0d2 100644
>> --- a/tools/perf/design.txt
>> +++ b/tools/perf/design.txt
>> @@ -440,3 +440,18 @@ by this process or by another, and doesn't affect any counters that
>>  this process has created on other processes.  It only enables or
>>  disables the group leaders, not any other members in the groups.
>>
>> +
>> +Arch requirements
>> +-----------------
>> +
>> +If your architecture does not have hardware performance metrics, you can
>> +still use the generic software counters based on hrtimers for sampling.
>> +
>> +So to start with, in order to add HAVE_PERF_COUNTERS to your Kconfig, you
>> +will need at least this:
>> +     - asm/perf_counter.h - a basic stub will suffice at first
>> +     - support for atomic64 types (and associated helper functions)
>> +     - set_perf_counter_pending() implemented
>> +
>> +If your architecture does have hardware capabilities, you can override the
>> +weak stub hw_perf_counter_init() to register hardware counters.
>
> It would be nice to see this in arch/Kconfig instead, as that tends to
> provide a centralized checklist for new features, especially when they
> are non-trivial. At least I found the arch/Kconfig bits very helpful for
> things like tracehook support, without having to grovel around
> Documentation for verbose design documents that I otherwise couldn't care
> less about.

i wouldnt mind moving all of the hidden HAVE_XXX stubs moved to
arch/Kconfig, but documentation doesnt really belong there.
especially in the case of ftrace where the document specifically for
arch porters is pages long (233 lines atm and it doesnt even cover the
really hard stuff).  the Kconfig help tip pointing to the right
document should be fine though of course.
config HAVE_XXXX
    bool
    help
      See some/place/where/the/arch/info/is/at/foo.txt

then there is no need to wade through irrelevant crap -- the Kconfig
pointed you to the right place
-mike

Re: [PATCH] perf_counters: start documenting HAVE_PERF_COUNTERS requirements

[Ingo Molnar]

* Mike Frysinger <vapier@gentoo.org> wrote:

> Help out arch porters who want to support perf counters by listing some
> basic requirements.
> 
> Signed-off-by: Mike Frysinger <vapier@gentoo.org>
> ---
> i imagine more details would be good, but this is a starting point and
> better than nothing
> 
>  init/Kconfig          |    2 ++
>  tools/perf/design.txt |   15 +++++++++++++++
>  2 files changed, 17 insertions(+), 0 deletions(-)
> 
> diff --git a/init/Kconfig b/init/Kconfig
> index c649657..20f85b1 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -936,6 +936,8 @@ config AIO
>  
>  config HAVE_PERF_COUNTERS
>  	bool
> +	help
> +	  See end of tools/perf/design.txt
>  
>  menu "Performance Counters"

Applied, thanks Mike! I have made a small change: i changed it from 
help text into a regular comment. We usually use help texts for 
interactive Kconfig options - but this is not one.

Thanks,

	Ingo

Re: [PATCH] perf_counters: start documenting HAVE_PERF_COUNTERS requirements

[Mike Frysinger]

On Fri, Jun 12, 2009 at 13:30, Ingo Molnar wrote:
> * Mike Frysinger <vapier@gentoo.org> wrote:
>> Help out arch porters who want to support perf counters by listing some
>> basic requirements.
>>
>> Signed-off-by: Mike Frysinger <vapier@gentoo.org>
>> ---
>> i imagine more details would be good, but this is a starting point and
>> better than nothing
>>
>>  init/Kconfig          |    2 ++
>>  tools/perf/design.txt |   15 +++++++++++++++
>>  2 files changed, 17 insertions(+), 0 deletions(-)
>>
>> diff --git a/init/Kconfig b/init/Kconfig
>> index c649657..20f85b1 100644
>> --- a/init/Kconfig
>> +++ b/init/Kconfig
>> @@ -936,6 +936,8 @@ config AIO
>>
>>  config HAVE_PERF_COUNTERS
>>       bool
>> +     help
>> +       See end of tools/perf/design.txt
>>
>>  menu "Performance Counters"
>
> Applied, thanks Mike! I have made a small change: i changed it from
> help text into a regular comment. We usually use help texts for
> interactive Kconfig options - but this is not one.

yes, but i like the help text because when i use the kconfig search
option, it shows up.  otherwise doing a search for HAVE_PERF_COUNTERS
shows nothing useful.
-mike

Re: [PATCH] perf_counters: start documenting HAVE_PERF_COUNTERS requirements

[Ingo Molnar]

* Mike Frysinger <vapier.adi@gmail.com> wrote:

> On Fri, Jun 12, 2009 at 13:30, Ingo Molnar wrote:
> > * Mike Frysinger <vapier@gentoo.org> wrote:
> >> Help out arch porters who want to support perf counters by listing some
> >> basic requirements.
> >>
> >> Signed-off-by: Mike Frysinger <vapier@gentoo.org>
> >> ---
> >> i imagine more details would be good, but this is a starting point and
> >> better than nothing
> >>
> >>  init/Kconfig          |    2 ++
> >>  tools/perf/design.txt |   15 +++++++++++++++
> >>  2 files changed, 17 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/init/Kconfig b/init/Kconfig
> >> index c649657..20f85b1 100644
> >> --- a/init/Kconfig
> >> +++ b/init/Kconfig
> >> @@ -936,6 +936,8 @@ config AIO
> >>
> >>  config HAVE_PERF_COUNTERS
> >>       bool
> >> +     help
> >> +       See end of tools/perf/design.txt
> >>
> >>  menu "Performance Counters"
> >
> > Applied, thanks Mike! I have made a small change: i changed it from
> > help text into a regular comment. We usually use help texts for
> > interactive Kconfig options - but this is not one.
> 
> yes, but i like the help text because when i use the kconfig 
> search option, it shows up.  otherwise doing a search for 
> HAVE_PERF_COUNTERS shows nothing useful.

When i did this modification i tried that in 'make menuconfig' and 
the help didnt show up. Is it only available in certain kconfig 
methods?

	Ingo

Re: [PATCH] perf_counters: start documenting HAVE_PERF_COUNTERS requirements

[Mike Frysinger]

On Fri, Jun 12, 2009 at 13:36, Ingo Molnar wrote:
> * Mike Frysinger <vapier.adi@gmail.com> wrote:
>> On Fri, Jun 12, 2009 at 13:30, Ingo Molnar wrote:
>> > * Mike Frysinger <vapier@gentoo.org> wrote:
>> >> Help out arch porters who want to support perf counters by listing some
>> >> basic requirements.
>> >>
>> >> Signed-off-by: Mike Frysinger <vapier@gentoo.org>
>> >> ---
>> >> i imagine more details would be good, but this is a starting point and
>> >> better than nothing
>> >>
>> >>  init/Kconfig          |    2 ++
>> >>  tools/perf/design.txt |   15 +++++++++++++++
>> >>  2 files changed, 17 insertions(+), 0 deletions(-)
>> >>
>> >> diff --git a/init/Kconfig b/init/Kconfig
>> >> index c649657..20f85b1 100644
>> >> --- a/init/Kconfig
>> >> +++ b/init/Kconfig
>> >> @@ -936,6 +936,8 @@ config AIO
>> >>
>> >>  config HAVE_PERF_COUNTERS
>> >>       bool
>> >> +     help
>> >> +       See end of tools/perf/design.txt
>> >>
>> >>  menu "Performance Counters"
>> >
>> > Applied, thanks Mike! I have made a small change: i changed it from
>> > help text into a regular comment. We usually use help texts for
>> > interactive Kconfig options - but this is not one.
>>
>> yes, but i like the help text because when i use the kconfig
>> search option, it shows up.  otherwise doing a search for
>> HAVE_PERF_COUNTERS shows nothing useful.
>
> When i did this modification i tried that in 'make menuconfig' and
> the help didnt show up. Is it only available in certain kconfig
> methods?

hrm, you're right.  not sure what i was thinking of.  sounds like an
enhancement request though for kconfig.
-mike

Re: [PATCH] perf_counters: start documenting HAVE_PERF_COUNTERS requirements

[Randy Dunlap]

Mike Frysinger wrote:
> On Fri, Jun 12, 2009 at 13:36, Ingo Molnar wrote:
>> * Mike Frysinger <vapier.adi@gmail.com> wrote:
>>> On Fri, Jun 12, 2009 at 13:30, Ingo Molnar wrote:
>>>> * Mike Frysinger <vapier@gentoo.org> wrote:
>>>>> Help out arch porters who want to support perf counters by listing some
>>>>> basic requirements.
>>>>>
>>>>> Signed-off-by: Mike Frysinger <vapier@gentoo.org>
>>>>> ---
>>>>> i imagine more details would be good, but this is a starting point and
>>>>> better than nothing
>>>>>
>>>>>  init/Kconfig          |    2 ++
>>>>>  tools/perf/design.txt |   15 +++++++++++++++
>>>>>  2 files changed, 17 insertions(+), 0 deletions(-)
>>>>>
>>>>> diff --git a/init/Kconfig b/init/Kconfig
>>>>> index c649657..20f85b1 100644
>>>>> --- a/init/Kconfig
>>>>> +++ b/init/Kconfig
>>>>> @@ -936,6 +936,8 @@ config AIO
>>>>>
>>>>>  config HAVE_PERF_COUNTERS
>>>>>       bool
>>>>> +     help
>>>>> +       See end of tools/perf/design.txt
>>>>>
>>>>>  menu "Performance Counters"
>>>> Applied, thanks Mike! I have made a small change: i changed it from
>>>> help text into a regular comment. We usually use help texts for
>>>> interactive Kconfig options - but this is not one.
>>> yes, but i like the help text because when i use the kconfig
>>> search option, it shows up.  otherwise doing a search for
>>> HAVE_PERF_COUNTERS shows nothing useful.
>> When i did this modification i tried that in 'make menuconfig' and
>> the help didnt show up. Is it only available in certain kconfig
>> methods?

There is no prompt string for it, so it's invisible in menuconfig.
xconfig has View options that can show it.

> hrm, you're right.  not sure what i was thinking of.  sounds like an
> enhancement request though for kconfig.

Could be.  Cc: Sam added.

-- 
~Randy
LPC 2009, Sept. 23-25, Portland, Oregon
http://linuxplumbersconf.org/2009/

Re: [PATCH] perf_counters: start documenting HAVE_PERF_COUNTERS requirements

[Sam Ravnborg]

On Fri, Jun 12, 2009 at 10:40:50AM -0700, Randy Dunlap wrote:
> Mike Frysinger wrote:
> > On Fri, Jun 12, 2009 at 13:36, Ingo Molnar wrote:
> >> * Mike Frysinger <vapier.adi@gmail.com> wrote:
> >>> On Fri, Jun 12, 2009 at 13:30, Ingo Molnar wrote:
> >>>> * Mike Frysinger <vapier@gentoo.org> wrote:
> >>>>> Help out arch porters who want to support perf counters by listing some
> >>>>> basic requirements.
> >>>>>
> >>>>> Signed-off-by: Mike Frysinger <vapier@gentoo.org>
> >>>>> ---
> >>>>> i imagine more details would be good, but this is a starting point and
> >>>>> better than nothing
> >>>>>
> >>>>>  init/Kconfig          |    2 ++
> >>>>>  tools/perf/design.txt |   15 +++++++++++++++
> >>>>>  2 files changed, 17 insertions(+), 0 deletions(-)
> >>>>>
> >>>>> diff --git a/init/Kconfig b/init/Kconfig
> >>>>> index c649657..20f85b1 100644
> >>>>> --- a/init/Kconfig
> >>>>> +++ b/init/Kconfig
> >>>>> @@ -936,6 +936,8 @@ config AIO
> >>>>>
> >>>>>  config HAVE_PERF_COUNTERS
> >>>>>       bool
> >>>>> +     help
> >>>>> +       See end of tools/perf/design.txt
> >>>>>
> >>>>>  menu "Performance Counters"
> >>>> Applied, thanks Mike! I have made a small change: i changed it from
> >>>> help text into a regular comment. We usually use help texts for
> >>>> interactive Kconfig options - but this is not one.
> >>> yes, but i like the help text because when i use the kconfig
> >>> search option, it shows up.  otherwise doing a search for
> >>> HAVE_PERF_COUNTERS shows nothing useful.
> >> When i did this modification i tried that in 'make menuconfig' and
> >> the help didnt show up. Is it only available in certain kconfig
> >> methods?
> 
> There is no prompt string for it, so it's invisible in menuconfig.
> xconfig has View options that can show it.
> 
> > hrm, you're right.  not sure what i was thinking of.  sounds like an
> > enhancement request though for kconfig.
> 
> Could be.  Cc: Sam added.

We do not want to show the invisible symbols.
But the added help text is still fine as it is there when you
grep the Kconfig file.

	Sam

Re: [PATCH] perf_counters: start documenting HAVE_PERF_COUNTERS requirements

[Randy Dunlap]

Sam Ravnborg wrote:
> On Fri, Jun 12, 2009 at 10:40:50AM -0700, Randy Dunlap wrote:
>> Mike Frysinger wrote:
>>> On Fri, Jun 12, 2009 at 13:36, Ingo Molnar wrote:
>>>> * Mike Frysinger <vapier.adi@gmail.com> wrote:
>>>>> On Fri, Jun 12, 2009 at 13:30, Ingo Molnar wrote:
>>>>>> * Mike Frysinger <vapier@gentoo.org> wrote:
>>>>>>> Help out arch porters who want to support perf counters by listing some
>>>>>>> basic requirements.
>>>>>>>
>>>>>>> Signed-off-by: Mike Frysinger <vapier@gentoo.org>
>>>>>>> ---
>>>>>>> i imagine more details would be good, but this is a starting point and
>>>>>>> better than nothing
>>>>>>>
>>>>>>>  init/Kconfig          |    2 ++
>>>>>>>  tools/perf/design.txt |   15 +++++++++++++++
>>>>>>>  2 files changed, 17 insertions(+), 0 deletions(-)
>>>>>>>
>>>>>>> diff --git a/init/Kconfig b/init/Kconfig
>>>>>>> index c649657..20f85b1 100644
>>>>>>> --- a/init/Kconfig
>>>>>>> +++ b/init/Kconfig
>>>>>>> @@ -936,6 +936,8 @@ config AIO
>>>>>>>
>>>>>>>  config HAVE_PERF_COUNTERS
>>>>>>>       bool
>>>>>>> +     help
>>>>>>> +       See end of tools/perf/design.txt
>>>>>>>
>>>>>>>  menu "Performance Counters"
>>>>>> Applied, thanks Mike! I have made a small change: i changed it from
>>>>>> help text into a regular comment. We usually use help texts for
>>>>>> interactive Kconfig options - but this is not one.
>>>>> yes, but i like the help text because when i use the kconfig
>>>>> search option, it shows up.  otherwise doing a search for
>>>>> HAVE_PERF_COUNTERS shows nothing useful.
>>>> When i did this modification i tried that in 'make menuconfig' and
>>>> the help didnt show up. Is it only available in certain kconfig
>>>> methods?
>> There is no prompt string for it, so it's invisible in menuconfig.
>> xconfig has View options that can show it.
>>
>>> hrm, you're right.  not sure what i was thinking of.  sounds like an
>>> enhancement request though for kconfig.
>> Could be.  Cc: Sam added.
> 
> We do not want to show the invisible symbols.

usually, yes.  But it can be very helpful to developers.
I use xconfig showing all symbols All Of The Time
(when not using menuconfig, that is).

> But the added help text is still fine as it is there when you
> grep the Kconfig file.


-- 
~Randy
LPC 2009, Sept. 23-25, Portland, Oregon
http://linuxplumbersconf.org/2009/

[tip:perfcounters/core] perf_counter: Start documenting HAVE_PERF_COUNTERS requirements

[tip-bot for Mike Frysinger]

Commit-ID:  3c1f287bf974b05ad75df3c462fccace10035fbd
Gitweb:     http://git.kernel.org/tip/3c1f287bf974b05ad75df3c462fccace10035fbd
Author:     Mike Frysinger <vapier@gentoo.org>
AuthorDate: Fri, 12 Jun 2009 13:17:43 -0400
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Fri, 12 Jun 2009 19:29:44 +0200

perf_counter: Start documenting HAVE_PERF_COUNTERS requirements

Help out arch porters who want to support perf counters by listing some
basic requirements.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1244827063-24046-1-git-send-email-vapier@gentoo.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
 init/Kconfig          |    3 +++
 tools/perf/design.txt |   15 +++++++++++++++
 2 files changed, 18 insertions(+), 0 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index c649657..e03959d 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -934,6 +934,9 @@ config AIO
           by some high performance threaded applications. Disabling
           this option saves about 7k.
 
+#
+# See tools/perf/design.txt about details:
+#
 config HAVE_PERF_COUNTERS
 	bool
 
diff --git a/tools/perf/design.txt b/tools/perf/design.txt
index 860e116..f71e0d2 100644
--- a/tools/perf/design.txt
+++ b/tools/perf/design.txt
@@ -440,3 +440,18 @@ by this process or by another, and doesn't affect any counters that
 this process has created on other processes.  It only enables or
 disables the group leaders, not any other members in the groups.
 
+
+Arch requirements
+-----------------
+
+If your architecture does not have hardware performance metrics, you can
+still use the generic software counters based on hrtimers for sampling.
+
+So to start with, in order to add HAVE_PERF_COUNTERS to your Kconfig, you
+will need at least this:
+	- asm/perf_counter.h - a basic stub will suffice at first
+	- support for atomic64 types (and associated helper functions)
+	- set_perf_counter_pending() implemented
+
+If your architecture does have hardware capabilities, you can override the
+weak stub hw_perf_counter_init() to register hardware counters.

[tip:perfcounters/core] perf_counter: Start documenting HAVE_PERF_COUNTERS requirements

[tip-bot for Mike Frysinger]

Commit-ID:  018df72dd01576ab199c6129233cdeaf1409958b
Gitweb:     http://git.kernel.org/tip/018df72dd01576ab199c6129233cdeaf1409958b
Author:     Mike Frysinger <vapier@gentoo.org>
AuthorDate: Fri, 12 Jun 2009 13:17:43 -0400
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Fri, 12 Jun 2009 19:37:30 +0200

perf_counter: Start documenting HAVE_PERF_COUNTERS requirements

Help out arch porters who want to support perf counters by listing some
basic requirements.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1244827063-24046-1-git-send-email-vapier@gentoo.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
 init/Kconfig          |    2 ++
 tools/perf/design.txt |   15 +++++++++++++++
 2 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index c649657..d3a5096 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -936,6 +936,8 @@ config AIO
 
 config HAVE_PERF_COUNTERS
 	bool
+	help
+	  See tools/perf/design.txt for details.
 
 menu "Performance Counters"
 
diff --git a/tools/perf/design.txt b/tools/perf/design.txt
index 860e116..f71e0d2 100644
--- a/tools/perf/design.txt
+++ b/tools/perf/design.txt
@@ -440,3 +440,18 @@ by this process or by another, and doesn't affect any counters that
 this process has created on other processes.  It only enables or
 disables the group leaders, not any other members in the groups.
 
+
+Arch requirements
+-----------------
+
+If your architecture does not have hardware performance metrics, you can
+still use the generic software counters based on hrtimers for sampling.
+
+So to start with, in order to add HAVE_PERF_COUNTERS to your Kconfig, you
+will need at least this:
+	- asm/perf_counter.h - a basic stub will suffice at first
+	- support for atomic64 types (and associated helper functions)
+	- set_perf_counter_pending() implemented
+
+If your architecture does have hardware capabilities, you can override the
+weak stub hw_perf_counter_init() to register hardware counters.