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Commit 00e145b6 authored by Manfred Spraul's avatar Manfred Spraul Committed by Linus Torvalds
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[PATCH] slab: removes local_irq_save()/local_irq_restore() pair 



Proposed by and based on a patch from Eric Dumazet <dada1@cosmosbay.com>:
This patch removes unnecessary critical section in ksize() function, as
cli/sti are rather expensive on modern CPUS.

It additionally adds a docbook entry for ksize() and further simplifies the
code.

Signed-Off-By: default avatarManfred Spraul <manfred@colorfullife.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 34342e86

mm/slab.c

+15 −11
Original line number Diff line number Diff line
@@ -3076,20 +3076,24 @@ ssize_t slabinfo_write(struct file *file, const char __user *buffer, 
}

#endif



/**

 * ksize - get the actual amount of memory allocated for a given object

 * @objp: Pointer to the object

 *

 * kmalloc may internally round up allocations and return more memory

 * than requested. ksize() can be used to determine the actual amount of

 * memory allocated. The caller may use this additional memory, even though

 * a smaller amount of memory was initially specified with the kmalloc call.

 * The caller must guarantee that objp points to a valid object previously

 * allocated with either kmalloc() or kmem_cache_alloc(). The object

 * must not be freed during the duration of the call.

 */

unsigned int ksize(const void *objp)

{

	kmem_cache_t *c;

	unsigned long flags;

	unsigned int size = 0;



	if (likely(objp != NULL)) {

		local_irq_save(flags);

		c = GET_PAGE_CACHE(virt_to_page(objp));

		size = kmem_cache_size(c);

		local_irq_restore(flags);

	}

	if (unlikely(objp == NULL))

		return 0;



	return size;

	return obj_reallen(GET_PAGE_CACHE(virt_to_page(objp)));

}