Re: [PATCH] mm/slab: make calculate_alignment() function static

Michal Hocko
2017-12-10T10:40:12Z

On Sun 10-12-17 17:01:32, Byongho Lee wrote:
> calculate_alignment() function is only used inside 'slab_common.c'.
> So make it static and let compiler do more optimizations.
>
> After this patch there's small improvements in 'text' and 'data' size.
>
> $ gcc --version
> gcc (GCC) 7.2.1 20171128
>
> Before:
> text data bss dec hex filename
> 9890457 3828702 1212364 14931523 e3d643 vmlinux
>
> After:
> text data bss dec hex filename
> 9890437 3828670 1212364 14931471 e3d60f vmlinux
>
> Also I fixed a 'style problem' reported by 'scripts/checkpatch.pl'.
>
> WARNING: Missing a blank line after declarations
> #53: FILE: mm/slab_common.c:286:
> + unsigned long ralign = cache_line_size();
> + while (size <= ralign / 2)
>
> Signed-off-by: Byongho Lee <bhlee.kernel@gmail.com>

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
> mm/slab.h | 3 ---
> mm/slab_common.c | 56 +++++++++++++++++++++++++++++---------------------------
> 2 files changed, 29 insertions(+), 30 deletions(-)
>
> diff --git a/mm/slab.h b/mm/slab.h
> index 028cdc7df67e..e894889dc24a 100644
> --- a/mm/slab.h
> +++ b/mm/slab.h
> @@ -79,9 +79,6 @@ extern const struct kmalloc_info_struct {
> unsigned long size;
> } kmalloc_info[];
>
> -unsigned long calculate_alignment(unsigned long flags,
> - unsigned long align, unsigned long size);
> -
> #ifndef CONFIG_SLOB
> /* Kmalloc array related functions */
> void setup_kmalloc_cache_index_table(void);
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 0d7fe71ff5e4..d25e7b56e20b 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -267,6 +267,35 @@ static inline void memcg_unlink_cache(struct kmem_cache *s)
> }
> #endif /* CONFIG_MEMCG && !CONFIG_SLOB */
>
> +/*
> + * Figure out what the alignment of the objects will be given a set of
> + * flags, a user specified alignment and the size of the objects.
> + */
> +static unsigned long calculate_alignment(unsigned long flags,
> + unsigned long align, unsigned long size)
> +{
> + /*
> + * If the user wants hardware cache aligned objects then follow that
> + * suggestion if the object is sufficiently large.
> + *
> + * The hardware cache alignment cannot override the specified
> + * alignment though. If that is greater then use it.
> + */
> + if (flags & SLAB_HWCACHE_ALIGN) {
> + unsigned long ralign;
> +
> + ralign = cache_line_size();
> + while (size <= ralign / 2)
> + ralign /= 2;
> + align = max(align, ralign);
> + }
> +
> + if (align < ARCH_SLAB_MINALIGN)
> + align = ARCH_SLAB_MINALIGN;
> +
> + return ALIGN(align, sizeof(void *));
> +}
> +
> /*
> * Find a mergeable slab cache
> */
> @@ -337,33 +366,6 @@ struct kmem_cache *find_mergeable(size_t size, size_t align,
> return NULL;
> }
>
> -/*
> - * Figure out what the alignment of the objects will be given a set of
> - * flags, a user specified alignment and the size of the objects.
> - */
> -unsigned long calculate_alignment(unsigned long flags,
> - unsigned long align, unsigned long size)
> -{
> - /*
> - * If the user wants hardware cache aligned objects then follow that
> - * suggestion if the object is sufficiently large.
> - *
> - * The hardware cache alignment cannot override the specified
> - * alignment though. If that is greater then use it.
> - */
> - if (flags & SLAB_HWCACHE_ALIGN) {
> - unsigned long ralign = cache_line_size();
> - while (size <= ralign / 2)
> - ralign /= 2;
> - align = max(align, ralign);
> - }
> -
> - if (align < ARCH_SLAB_MINALIGN)
> - align = ARCH_SLAB_MINALIGN;
> -
> - return ALIGN(align, sizeof(void *));
> -}
> -
> static struct kmem_cache *create_cache(const char *name,
> size_t object_size, size_t size, size_t align,
> unsigned long flags, void (*ctor)(void *),
> --
> 2.15.1
>
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--
Michal Hocko
SUSE Labs