Messages in this thread Patch in this message | | | Date | Wed, 26 Apr 2006 13:57:04 +0300 (EEST) | From | Pekka J Enberg <> | Subject | Re: [PATCH] likely cleanup: remove unlikely for kfree(NULL) |
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On Wed, 26 April 2006 10:27:18 +0200, Arjan van de Ven wrote: > > > what I would like is kfree to become an inline wrapper that does the > > > null check inline, that way gcc can optimize it out (and it will in 4.1 > > > with the VRP pass) if gcc can prove it's not NULL.
On Wed, 2006-04-26 at 12:05 +0200, Jörn Engel wrote: > > How well can gcc optimize this case?
On Wed, 26 Apr 2006, Arjan van de Ven wrote: > if you deref'd the pointer it'll optimize it away (assuming a new enough > gcc, like 4.1)
Here are the numbers for allyesconfig on my setup.
Pekka
gcc version 3.4.5 (Gentoo 3.4.5-r1, ssp-3.4.5-1.0, pie-8.7.9)
text data bss dec hex filename 24910301 6946478 2092332 33949111 20605b7 vmlinux 24934157 6946530 2092332 33973019 206631b vmlinux-inline-kfree
diff --git a/include/linux/slab.h b/include/linux/slab.h index 3af03b1..1b4b3bb 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -148,7 +148,14 @@ static inline void *kcalloc(size_t n, si return kzalloc(n * size, flags); } -extern void kfree(const void *); +extern void __kfree(const void *); + +static inline void kfree(const void *p) +{ + if (unlikely(p)) + __kfree(p); +} + extern unsigned int ksize(const void *); #ifdef CONFIG_NUMA diff --git a/mm/slab.c b/mm/slab.c index e6ef9bd..1f63787 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -3367,7 +3367,7 @@ void kmem_cache_free(struct kmem_cache * EXPORT_SYMBOL(kmem_cache_free); /** - * kfree - free previously allocated memory + * __kfree - free previously allocated memory * @objp: pointer returned by kmalloc. * * If @objp is NULL, no operation is performed. @@ -3375,13 +3375,11 @@ EXPORT_SYMBOL(kmem_cache_free); * Don't free memory not originally allocated by kmalloc() * or you will run into trouble. */ -void kfree(const void *objp) +void __kfree(const void *objp) { struct kmem_cache *c; unsigned long flags; - if (unlikely(!objp)) - return; local_irq_save(flags); kfree_debugcheck(objp); c = virt_to_cache(objp); @@ -3389,7 +3387,7 @@ void kfree(const void *objp) __cache_free(c, (void *)objp); local_irq_restore(flags); } -EXPORT_SYMBOL(kfree); +EXPORT_SYMBOL(__kfree); #ifdef CONFIG_SMP /** - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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