On Sat, 24 Sep 2011, Tetsuo Handa wrote:
> If CONFIG_OPTIMIZE_INLINING=y, /proc/slab_allocators shows entries like
>
> size-512: 5 kzalloc+0xb/0x10
> size-256: 31 kzalloc+0xb/0x10
>
> which are useless for debugging.
> Use "__always_inline" rather than "inline" in order to make
> /proc/slab_allocators show caller of kzalloc() if caller tracking is enabled.
>
This is only an issue for gcc 4.x compilers, correct?
> Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
> ----------
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index 573c809..2b745c0 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -188,6 +188,18 @@ size_t ksize(const void *);
> #else
> #include <linux/slab_def.h>
> #endif
> +/*
> + * /proc/slab_allocator needs _RET_IP_ value. If CONFIG_OPTIMIZE_INLINING=y,
> + * use of "inline" causes compilers to pass address of kzalloc() etc. rather
> + * than address of caller. Thus, use "__always_inline" if _RET_IP_ value is
> + * needed.
> + */
> +#if defined(CONFIG_DEBUG_SLAB) || defined(CONFIG_SLUB) || \
> + (defined(CONFIG_SLAB) && defined(CONFIG_TRACING))
/proc/slab_allocators is for CONFIG_SLAB only, so why is this being done
for slub when it already uses trace points with _RET_IP_?
> +#define slabtrace_inline __always_inline
> +#else
> +#define slabtrace_inline inline
> +#endif
>
> /**
> * kcalloc - allocate memory for an array. The memory is set to zero.
> @@ -240,7 +252,7 @@ size_t ksize(const void *);
> * for general use, and so are not documented here. For a full list of
> * potential flags, always refer to linux/gfp.h.
> */
> -static inline void *kcalloc(size_t n, size_t size, gfp_t flags)
> +static slabtrace_inline void *kcalloc(size_t n, size_t size, gfp_t flags)
> {
> if (size != 0 && n > ULONG_MAX / size)
> return NULL;
> @@ -258,19 +270,19 @@ static inline void *kcalloc(size_t n, size_t size, gfp_t flags)
> * if available. Equivalent to kmalloc() in the non-NUMA single-node
> * case.
> */
> -static inline void *kmalloc_node(size_t size, gfp_t flags, int node)
> +static slabtrace_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
> {
> return kmalloc(size, flags);
> }
>
> -static inline void *__kmalloc_node(size_t size, gfp_t flags, int node)
> +static slabtrace_inline void *__kmalloc_node(size_t size, gfp_t flags, int node)
> {
> return __kmalloc(size, flags);
> }
>
> void *kmem_cache_alloc(struct kmem_cache *, gfp_t);
>
> -static inline void *kmem_cache_alloc_node(struct kmem_cache *cachep,
> +static slabtrace_inline void *kmem_cache_alloc_node(struct kmem_cache *cachep,
> gfp_t flags, int node)
> {
> return kmem_cache_alloc(cachep, flags);
> @@ -325,7 +337,7 @@ extern void *__kmalloc_node_track_caller(size_t, gfp_t, int, unsigned long);
> /*
> * Shortcuts
> */
> -static inline void *kmem_cache_zalloc(struct kmem_cache *k, gfp_t flags)
> +static slabtrace_inline void *kmem_cache_zalloc(struct kmem_cache *k, gfp_t flags)
> {
> return kmem_cache_alloc(k, flags | __GFP_ZERO);
> }
> @@ -335,7 +347,7 @@ static inline void *kmem_cache_zalloc(struct kmem_cache *k, gfp_t flags)
> * @size: how many bytes of memory are required.
> * @flags: the type of memory to allocate (see kmalloc).
> */
> -static inline void *kzalloc(size_t size, gfp_t flags)
> +static slabtrace_inline void *kzalloc(size_t size, gfp_t flags)
> {
> return kmalloc(size, flags | __GFP_ZERO);
> }
> @@ -346,7 +358,7 @@ static inline void *kzalloc(size_t size, gfp_t flags)
> * @flags: the type of memory to allocate (see kmalloc).
> * @node: memory node from which to allocate
> */
> -static inline void *kzalloc_node(size_t size, gfp_t flags, int node)
> +static slabtrace_inline void *kzalloc_node(size_t size, gfp_t flags, int node)
> {
> return kmalloc_node(size, flags | __GFP_ZERO, node);
> }
>
So this is going against the inlining algorithms in gcc 4.x which will
make the kernel image significantly larger even though there seems to be
no benefit unless you have CONFIG_DEBUG_SLAB_LEAK, although this patch
changes behavior for every system running CONFIG_SLAB with tracing
support.
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