Re: [PATCH] Better document profile=

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 16 Oct 2007 22:16:47 -0700
"Russ Dill" <russ.dill@gmail.com> wrote:

> Be more explicit on what the step/bucket size accomplishes.
> 
> Signed-off-by: Russ Dill <Russ.Dill@gmail.com>
> ---
>  Documentation/kernel-parameters.txt |    5 ++++-
>  1 files changed, 4 insertions(+), 1 deletions(-)
> 
> diff --git a/Documentation/kernel-parameters.txt
> b/Documentation/kernel-parameters.txt
> index eb24799..3c6fd27 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -1427,7 +1427,10 @@ and is between 256 and 4096 characters. It is
> defined in the file

Your email client is wordwrapping the patches.

>  			Format: [schedule,]<number>
>  			Param: "schedule" - profile schedule points.
>  			Param: <number> - step/bucket size as a power of 2 for
> -				statistical time based profiling.
> +				statistical time based profiling. A value of
> +				2 will provide a granularity of 4 bytes, a
> +				value of 3 will provide a granularity of 8
> +				bytes and so on.
>  			Param: "sleep" - profile D-state sleeping (millisecs)

Actually the prof_shift isn't in units of bytes: it is in units of
sizeof(unsigned long).

So on a 64-bit kernel, prof_shift=2 will give a granularity of 8<<2 bytes
and on a 32-bit kernel, prof_shift=3 will give a granularity of 4<<3 bytes.