2009-01-12 05:57:50

by Rakib Mullick

Subject: [PATCH] init: Reduce text space by removing a variable.

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 <[email protected]>

--- 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) {
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;

2009-01-12 06:43:23

by Sergio Luis

Subject: Re: [PATCH] init: Reduce text space by removing a variable.

On Mon, Jan 12, 2009 at 2:57 AM, Rakib Mullick <[email protected]> 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 <[email protected]>
>
> --- 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.