linux-kernel - Re: [PATCH] scripts/checkkconfig.py: find unused Kconfig parameters

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Date:	Tue, 29 Oct 2013 19:06:19 +0100
From:	"Yann E. MORIN" <yann.morin.1998@...e.fr>
To:	Michael Opdenacker <michael.opdenacker@...e-electrons.com>
Cc:	mmarek@...e.cz, akpm@...ux-foundation.org, joe@...ches.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scripts/checkkconfig.py: find unused Kconfig parameters

Michael, All,

On 2013-10-24 07:23 +0200, Michael Opdenacker spake thusly:
> This is the first version of a script to look for
> Kconfig parameters which are still defined but no longer
> used in the kernel source code.
> 
> The script may be extended in the future to perform
> more checks. This explains why a rather generic name was chosen.
> 
> Several issues have already been reported and fixed
> thanks to the use of this script. It is time to share it now!

I'm not much of a Python guy, so I'll gleefully rely on the previous
comments to guide you in your endeavour.

/me is feeling poetical, tonight! ;-)

I however have a suggestion, see below.

> Signed-off-by: Michael Opdenacker <michael.opdenacker@...e-electrons.com>
> ---
>  scripts/checkkconfig.py | 131 ++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 131 insertions(+)
>  create mode 100755 scripts/checkkconfig.py
> 
> diff --git a/scripts/checkkconfig.py b/scripts/checkkconfig.py
> new file mode 100755
> index 0000000..4155656
> --- /dev/null
> +++ b/scripts/checkkconfig.py
> @@ -0,0 +1,131 @@
[--SNIP--]
> +def count_param(param):
> +
> +    global source_file, bad_params_in_file
> +
> +    if os.path.isdir('.git'):
> +       # Use git grep when available
> +       count = subprocess.check_output('git grep ' + param + '| grep -v defconfig | wc -l', shell=True)
> +    else:
> +       # Fallback to regular grep
> +       count = subprocess.check_output('grep -R ' + param + ' . | grep -v defconfig | wc -l', shell=True)
> +
> +    num = int(count.strip())
> +
> +    if num == 1:
> +       'WARNING: parameter ' + param + ' is used nowhere'
> +
> +       file=source_file[param]
> +
> +       if bad_params_in_file.has_key(file):
> +          bad_params_in_file[file].append(param)
> +       else:
> +	  bad_params_in_file[file]=[param]
> +
> +
> +########################################################
> +# Main program
> +########################################################
[--SNIP--]
> +for param in has_select.keys():
> +
> +    # Progress information... running the script can take hours!

I guess all these grep spawning are what makes it slow.

I wonder if it would not be possible to invert the loop (in pseudo
Python code):

    for f in all_interesting_files:
        read f in memory
        for s in all_symbols:
            if symbol is in f:
                remove f from all_symbols
                break the inner-most loop

This way:
  - you scan the tree only once
  - as soon as a symbol is matched, it is removed, thus decreasing
    the amount of checks done in further loops.

Regards,
Yann E. MORIN.

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