* [tip: sched/psi] devres: Slightly optimize alloc_dr()
@ 2022-09-09 14:00 tip-bot2 for Christophe JAILLET
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From: tip-bot2 for Christophe JAILLET @ 2022-09-09 14:00 UTC (permalink / raw)
To: linux-tip-commits
Cc: Christophe JAILLET, Greg Kroah-Hartman, x86, linux-kernel
The following commit has been merged into the sched/psi branch of tip:
Commit-ID: 61742a7cd5b194d2cc52d78de8ec6967634a4cd6
Gitweb: https://git.kernel.org/tip/61742a7cd5b194d2cc52d78de8ec6967634a4cd6
Author: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
AuthorDate: Wed, 20 Jul 2022 23:26:36 +02:00
Committer: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CommitterDate: Thu, 01 Sep 2022 18:17:14 +02:00
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>
---
drivers/base/devres.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/base/devres.c b/drivers/base/devres.c
index 864d0b3..4ab2b50 100644
--- a/drivers/base/devres.c
+++ b/drivers/base/devres.c
@@ -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;
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