linux-kernel - [PATCH] slab: Make allocations with GFP

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Date:	Tue, 10 Sep 2013 17:02:51 -0700
From:	Joe Perches <joe@...ches.com>
To:	Christoph Lameter <cl@...ux-foundation.org>,
	Pekka Enberg <penberg@...nel.org>,
	Matt Mackall <mpm@...enic.com>
Cc:	linux-mm <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] slab: Make allocations with GFP_ZERO slightly more efficient

Use the likely mechanism already around valid
pointer tests to better choose when to memset
to 0 allocations with __GFP_ZERO

Signed-off-by: Joe Perches <joe@...ches.com>
---
 mm/slab.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index 2580db0..94e7e54 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3392,11 +3392,11 @@ slab_alloc_node(struct kmem_cache *cachep, gfp_t flags, int nodeid,
 	kmemleak_alloc_recursive(ptr, cachep->object_size, 1, cachep->flags,
 				 flags);
 
-	if (likely(ptr))
+	if (likely(ptr)) {
 		kmemcheck_slab_alloc(cachep, flags, ptr, cachep->object_size);
-
-	if (unlikely((flags & __GFP_ZERO) && ptr))
-		memset(ptr, 0, cachep->object_size);
+		if (unlikely(flags & __GFP_ZERO))
+			memset(ptr, 0, cachep->object_size);
+	}
 
 	return ptr;
 }
@@ -3457,11 +3457,11 @@ slab_alloc(struct kmem_cache *cachep, gfp_t flags, unsigned long caller)
 				 flags);
 	prefetchw(objp);
 
-	if (likely(objp))
+	if (likely(objp)) {
 		kmemcheck_slab_alloc(cachep, flags, objp, cachep->object_size);
-
-	if (unlikely((flags & __GFP_ZERO) && objp))
-		memset(objp, 0, cachep->object_size);
+		if (unlikely(flags & __GFP_ZERO))
+			memset(objp, 0, cachep->object_size);
+	}
 
 	return objp;
 }


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