How to profile the kernel during its initialization?

How to profile the kernel during its initialization?

[Zheng Da]

Hello

Can we profile the kernel during its initialization? perf is
initialized in an early stage in start_kernel(), but it seems there
are no command-line parameters to enable it.
Does anyone have any ideas how to profile the kernel during its
initialization (before user space programs start to run)? I think
someone should have the similar problem as me, and there should be
some solutions.

Thanks,
Da

How to profile the kernel during its initialization?

[Vladimir Murzin]

On Wed, Jul 6, 2011 at 12:47 AM, Zheng Da <zhengda1936@gmail.com> wrote:
> Hello
>
> Can we profile the kernel during its initialization? perf is
> initialized in an early stage in start_kernel(), but it seems there
> are no command-line parameters to enable it.
> Does anyone have any ideas how to profile the kernel during its
> initialization (before user space programs start to run)? I think
> someone should have the similar problem as me, and there should be
> some solutions.
>
> Thanks,
> Da
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>

Hi Da,

Have a look at ftrace. It could be used to profile initcalls.
Just add following boot options:

initcall_debug, ftrace=initcall

More details on
http://www.omappedia.org/wiki/Installing_and_Using_Ftrace#Boot_Tracer

How to profile the kernel during its initialization?

[Da Zheng]

On 07/05/11 21:17, Vladimir Murzin wrote:
> On Wed, Jul 6, 2011 at 12:47 AM, Zheng Da<zhengda1936@gmail.com>  wrote:
>> Hello
>>
>> Can we profile the kernel during its initialization? perf is
>> initialized in an early stage in start_kernel(), but it seems there
>> are no command-line parameters to enable it.
>> Does anyone have any ideas how to profile the kernel during its
>> initialization (before user space programs start to run)? I think
>> someone should have the similar problem as me, and there should be
>> some solutions.
>>
>> Thanks,
>> Da
>>
>> _______________________________________________
>> Kernelnewbies mailing list
>> Kernelnewbies at kernelnewbies.org
>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>>
> Hi Da,
>
> Have a look at ftrace. It could be used to profile initcalls.
> Just add following boot options:
>
> initcall_debug, ftrace=initcall
>
> More details on
> http://www.omappedia.org/wiki/Installing_and_Using_Ftrace#Boot_Tracer
Thanks Vladimir. initcall_debug can show me which initcalls use most of 
time.
but the initcall tracer has already been abandoned. I use v2.6.38. If I 
enable the function tracer, then it generates too much data, and the old 
data is overwritten. Is function tracer or function graph tracer 
available for tracing initcalls?

Da

How to profile the kernel during its initialization?

[Da Zheng]

On 07/05/11 21:17, Vladimir Murzin wrote:
> On Wed, Jul 6, 2011 at 12:47 AM, Zheng Da<zhengda1936@gmail.com>  wrote:
>> Hello
>>
>> Can we profile the kernel during its initialization? perf is
>> initialized in an early stage in start_kernel(), but it seems there
>> are no command-line parameters to enable it.
>> Does anyone have any ideas how to profile the kernel during its
>> initialization (before user space programs start to run)? I think
>> someone should have the similar problem as me, and there should be
>> some solutions.
>>
>> Thanks,
>> Da
>>
>> _______________________________________________
>> Kernelnewbies mailing list
>> Kernelnewbies at kernelnewbies.org
>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>>
> Hi Da,
>
> Have a look at ftrace. It could be used to profile initcalls.
> Just add following boot options:
>
> initcall_debug, ftrace=initcall
>
> More details on
> http://www.omappedia.org/wiki/Installing_and_Using_Ftrace#Boot_Tracer
I'm reading the code of ftrace. Most of tracers are registered in device 
initcalls. So if I enable a tracer in the kernel parameters, it only 
starts to work after device initcalls. Actually, what I really want to 
trace is device initcalls.

Is there any reason why tracers have to be registered in device 
initcalls? Can I move them to an earlier place? at least some of them, 
such as function tracer and function graph tracer.

Thanks,
Da