2015-05-04 15:28:04

by Rasmus Villemoes

Subject: [PATCH] mm: only define hashdist variable when needed

For !CONFIG_NUMA, hashdist will always be 0, since it's setter is
otherwise compiled out. So we can save 4 bytes of data and some .text
(although mostly in __init functions) by only defining it for
CONFIG_NUMA.

Signed-off-by: Rasmus Villemoes <[email protected]>
---
include/linux/bootmem.h | 8 ++++----
mm/page_alloc.c | 2 +-
2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/linux/bootmem.h b/include/linux/bootmem.h
index 0995c2de8162..f589222bfa87 100644
--- a/include/linux/bootmem.h
+++ b/include/linux/bootmem.h
@@ -357,12 +357,12 @@ extern void *alloc_large_system_hash(const char *tablename,
/* Only NUMA needs hash distribution. 64bit NUMA architectures have
* sufficient vmalloc space.
*/
-#if defined(CONFIG_NUMA) && defined(CONFIG_64BIT)
-#define HASHDIST_DEFAULT 1
+#ifdef CONFIG_NUMA
+#define HASHDIST_DEFAULT IS_ENABLED(CONFIG_64BIT)
+extern int hashdist; /* Distribute hashes across NUMA nodes? */
#else
-#define HASHDIST_DEFAULT 0
+#define hashdist (0)
#endif
-extern int hashdist; /* Distribute hashes across NUMA nodes? */


#endif /* _LINUX_BOOTMEM_H */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ebffa0e4a9c0..159dbbc3375d 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6013,9 +6013,9 @@ out:
return ret;
}

+#ifdef CONFIG_NUMA
int hashdist = HASHDIST_DEFAULT;

-#ifdef CONFIG_NUMA
static int __init set_hashdist(char *str)
{
if (!str)
--
2.1.3

2015-05-06 11:12:49

by Michal Hocko

Subject: Re: [PATCH] mm: only define hashdist variable when needed

On Mon 04-05-15 17:27:29, Rasmus Villemoes wrote:
> For !CONFIG_NUMA, hashdist will always be 0, since it's setter is
> otherwise compiled out. So we can save 4 bytes of data and some .text
> (although mostly in __init functions) by only defining it for
> CONFIG_NUMA.
>
> Signed-off-by: Rasmus Villemoes <[email protected]>

Reviewed-by: Michal Hocko <[email protected]>

> ---
> include/linux/bootmem.h | 8 ++++----
> mm/page_alloc.c | 2 +-
> 2 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/bootmem.h b/include/linux/bootmem.h
> index 0995c2de8162..f589222bfa87 100644
> --- a/include/linux/bootmem.h
> +++ b/include/linux/bootmem.h
> @@ -357,12 +357,12 @@ extern void *alloc_large_system_hash(const char *tablename,
> /* Only NUMA needs hash distribution. 64bit NUMA architectures have
> * sufficient vmalloc space.
> */
> -#if defined(CONFIG_NUMA) && defined(CONFIG_64BIT)
> -#define HASHDIST_DEFAULT 1
> +#ifdef CONFIG_NUMA
> +#define HASHDIST_DEFAULT IS_ENABLED(CONFIG_64BIT)
> +extern int hashdist; /* Distribute hashes across NUMA nodes? */
> #else
> -#define HASHDIST_DEFAULT 0
> +#define hashdist (0)
> #endif
> -extern int hashdist; /* Distribute hashes across NUMA nodes? */
>
>
> #endif /* _LINUX_BOOTMEM_H */
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index ebffa0e4a9c0..159dbbc3375d 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -6013,9 +6013,9 @@ out:
> return ret;
> }
>
> +#ifdef CONFIG_NUMA
> int hashdist = HASHDIST_DEFAULT;
>
> -#ifdef CONFIG_NUMA
> static int __init set_hashdist(char *str)
> {
> if (!str)
> --
> 2.1.3
>

--
Michal Hocko
SUSE Labs

2015-05-06 19:50:10

by David Rientjes

Subject: Re: [PATCH] mm: only define hashdist variable when needed

On Mon, 4 May 2015, Rasmus Villemoes wrote:

> For !CONFIG_NUMA, hashdist will always be 0, since it's setter is
> otherwise compiled out. So we can save 4 bytes of data and some .text
> (although mostly in __init functions) by only defining it for
> CONFIG_NUMA.
>
> Signed-off-by: Rasmus Villemoes <[email protected]>

Acked-by: David Rientjes <[email protected]>