linux-kernel - [PATCH] mm: faster kmalloc

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Message-ID: <20160627213454.GA2440@p183.telecom.by>
Date:	Tue, 28 Jun 2016 00:34:55 +0300
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	akpm@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] mm: faster kmalloc_array(), kcalloc()

When both arguments to kmalloc_array() or kcalloc() are known at
compile time then their product is known at compile time
but search for kmalloc cache happens at runtime not at compile time.

Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
---

 include/linux/slab.h |    2 ++
 1 file changed, 2 insertions(+)

--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -565,6 +565,8 @@ static inline void *kmalloc_array(size_t n, size_t size, gfp_t flags)
 {
 	if (size != 0 && n > SIZE_MAX / size)
 		return NULL;
+	if (__builtin_constant_p(n) && __builtin_constant_p(size))
+		return kmalloc(n * size, flags);
 	return __kmalloc(n * size, flags);
 }