[PATCH] no need to align .modinfo strings

[PATCH] no need to align .modinfo strings

[Jan Beulich]

Their use is not performance critical, and hence it seems better to
save some space.

Signed-off-by: Jan Beulich <jbeulich@novell.com>

---
 include/linux/moduleparam.h |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- linux-2.6.36-rc3/include/linux/moduleparam.h
+++ 2.6.36-rc3-modinfo-align/include/linux/moduleparam.h
@@ -21,8 +21,8 @@
 #define __module_cat(a,b) ___module_cat(a,b)
 #define __MODULE_INFO(tag, name, info)					  \
 static const char __module_cat(name,__LINE__)[]				  \
-  __used								  \
-  __attribute__((section(".modinfo"),unused)) = __stringify(tag) "=" info
+  __used __attribute__((section(".modinfo"), unused, aligned(1)))	  \
+  = __stringify(tag) "=" info
 #else  /* !MODULE */
 #define __MODULE_INFO(tag, name, info)
 #endif

Re: [PATCH] no need to align .modinfo strings

[Rusty Russell]

On Thu, 2 Sep 2010 09:54:40 pm Jan Beulich wrote:
> Their use is not performance critical, and hence it seems better to
> save some space.
> 
> Signed-off-by: Jan Beulich <jbeulich@novell.com>

Acked-by: Rusty Russell <rusty@rustcorp.com.au>

The real question is: why is gcc aligning these?  Should it be aligning
any string literals at all?  If so, should we look for other such wastes
of space?

Thanks,
Rusty.

> --- linux-2.6.36-rc3/include/linux/moduleparam.h
> +++ 2.6.36-rc3-modinfo-align/include/linux/moduleparam.h
> @@ -21,8 +21,8 @@
>  #define __module_cat(a,b) ___module_cat(a,b)
>  #define __MODULE_INFO(tag, name, info)					  \
>  static const char __module_cat(name,__LINE__)[]				  \
> -  __used								  \
> -  __attribute__((section(".modinfo"),unused)) = __stringify(tag) "=" info
> +  __used __attribute__((section(".modinfo"), unused, aligned(1)))	  \
> +  = __stringify(tag) "=" info
>  #else  /* !MODULE */
>  #define __MODULE_INFO(tag, name, info)
>  #endif
> 
> 
> 

Re: [PATCH] no need to align .modinfo strings

[Jan Beulich]

>>> On 06.09.10 at 10:19, Rusty Russell <rusty@rustcorp.com.au> wrote:
> On Thu, 2 Sep 2010 09:54:40 pm Jan Beulich wrote:
>> Their use is not performance critical, and hence it seems better to
>> save some space.
>> 
>> Signed-off-by: Jan Beulich <jbeulich@novell.com>
> 
> Acked-by: Rusty Russell <rusty@rustcorp.com.au>
> 
> The real question is: why is gcc aligning these?  Should it be aligning

A performance consideration for those cases where strings are being
used a lot, I believe.

> any string literals at all?  If so, should we look for other such wastes
> of space?

I think we should, at least I'm keeping an eye open to spot any such.

Jan