linux-kernel - Re: [PATCH] init: Reduce text space by removing a variable.

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Date:	Mon, 12 Jan 2009 03:43:10 -0300
From:	"Sergio Luis" <eeeesti@...il.com>
To:	"Rakib Mullick" <rakib.mullick@...il.com>
Cc:	"Linux-kernel Mailing List" <linux-kernel@...r.kernel.org>,
	mingo@...e.hu, akpm@...ux-foundation.org
Subject: Re: [PATCH] init: Reduce text space by removing a variable.

On Mon, Jan 12, 2009 at 2:57 AM, Rakib Mullick <rakib.mullick@...il.com> wrote:
> Impact: Reduce some text space.
>
> We can carryout the function 'raid_setup' without the variable 'len'
> and using a bit compiler optimization. Which also removes 8 bytes of
> text space on my x86 system.
>
> Signed-off-by: Rakib Mullick <rakib.mullick@...il.com>
>
> --- linux-2.6-orig/init/do_mounts_md.c  2009-01-12 09:53:09.000000000 +0600
> +++ linux-2.6/init/do_mounts_md.c       2009-01-12 11:12:39.734543784 +0600
> @@ -243,17 +243,17 @@ static void __init md_setup_drive(void)
>
>  static int __init raid_setup(char *str)
>  {
> -       int len, pos;
> +       int pos;
>
> -       len = strlen(str) + 1;
>        pos = 0;
>
> -       while (pos < len) {
> +       while (pos < strlen(str) + 1) {

doesn't calling strlen for every iteration (and in the else statement)
add an unneeded (and unwanted) overhead?

>                char *comma = strchr(str+pos, ',');
>                int wlen;
>                if (comma)
>                        wlen = (comma-str)-pos;
> -               else    wlen = (len-1)-pos;
> +               else
> +                       wlen = strlen(str)-pos;
>
>                if (!strncmp(str, "noautodetect", wlen))
>                        raid_noautodetect = 1;
> --

Sergio.
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