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devres: Slightly optimize alloc_dr() 

If the gfp flag used for the memory allocation already has __GFP_ZERO,
then there is no need to explicitly clear the "struct devres_node". It is
already zeroed.

This saves a few cycles when using devm_zalloc() and co.

In the case of devres_alloc() (which calls __devres_alloc_node()), the
compiler could remove the test and the memset() because it should be able
to see that the __GFP_ZERO flag is set.
So this would make the code both faster and smaller.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/d255bd871484e63cdd628e819f929e2df59afb02.1658352383.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Christophe JAILLET 2022-07-20 23:26:36 +02:00 committed by Greg Kroah-Hartman
parent 6bb7ea3afd
commit 61742a7cd5
1 changed files with 3 additions and 1 deletions
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4
drivers/base/devres.c
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@ -117,7 +117,9 @@ static __always_inline struct devres * alloc_dr(dr_release_t release,
if (unlikely(!dr))
return NULL;
memset(dr, 0, offsetof(struct devres, data));
/* No need to clear memory twice */
if (!(gfp & __GFP_ZERO))
memset(dr, 0, offsetof(struct devres, data));
INIT_LIST_HEAD(&dr->node.entry);
dr->node.release = release;