2011-02-23 17:15:00

by Richard Kennedy

Subject: [PATCH] module: reorder kparam_array to remove alignment padding on 64 bit builds

Reorder structure kparam_array to remove 8 bytes of alignment padding on
64 bit builds, dropping its size from 40 to 32 bytes.

Also update the macro module_param_array_named to initialise the
structure using its member names to allow it to be changed without
touching all its call sites.

'git grep' finds module_param_array in 1037 places so this patch will
save a small amount of data space across many modules.

Signed-off-by: Richard Kennedy <[email protected]>
----

patch against v2.6.38-rc6
compiled & tested on x86_64

regards
Richard



diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
index 07b4195..ddaae98 100644
--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -67,9 +67,9 @@ struct kparam_string {
struct kparam_array
{
unsigned int max;
+ unsigned int elemsize;
unsigned int *num;
const struct kernel_param_ops *ops;
- unsigned int elemsize;
void *elem;
};

@@ -371,8 +371,9 @@ extern int param_get_invbool(char *buffer, const struct kernel_param *kp);
*/
#define module_param_array_named(name, array, type, nump, perm) \
static const struct kparam_array __param_arr_##name \
- = { ARRAY_SIZE(array), nump, &param_ops_##type, \
- sizeof(array[0]), array }; \
+ = { .max = ARRAY_SIZE(array), .num = nump, \
+ .ops = &param_ops_##type, \
+ .elemsize = sizeof(array[0]), .elem = array }; \
__module_param_call(MODULE_PARAM_PREFIX, name, \
&param_array_ops, \
.arr = &__param_arr_##name, \