[PATCH] slab: reduce fragmentation due to kmem_cache_alloc_node

Attached is a patch that fixes the fragmentation that Badri noticed with
kmem_cache_alloc_node.

kmem_cache_alloc_node tries to allocate memory from a given node. The
current implementation contains two bugs:

- the node aware code was used even for !CONFIG_NUMA systems.  Fix:
  inline function that redefines kmem_cache_alloc_node as kmem_cache_alloc
  for !CONFIG_NUMA.

- the code always allocated a new slab for each new allocation.  This
  caused severe fragmentation.  Fix: walk the slabp lists and search for a
  matching page instead of allocating a new page.

- the patch also adds a new statistics field for node-local allocs.  They
  should be rare - the codepath is quite slow, especially compared to the
  normal kmem_cache_alloc.

Signed-Off-By: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/include/linux/slab.h b/include/linux/slab.h
index e51014cb24a0..7c81a7863b99 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -61,7 +61,14 @@ extern kmem_cache_t *kmem_cache_create(const char *, size_t, size_t, unsigned lo
 extern int kmem_cache_destroy(kmem_cache_t *);
 extern int kmem_cache_shrink(kmem_cache_t *);
 extern void *kmem_cache_alloc(kmem_cache_t *, int);
+#ifdef CONFIG_NUMA
 extern void *kmem_cache_alloc_node(kmem_cache_t *, int);
+#else
+static inline void *kmem_cache_alloc_node(kmem_cache_t *cachep, int node)
+{
+	return kmem_cache_alloc(cachep, GFP_KERNEL);
+}
+#endif
 extern void kmem_cache_free(kmem_cache_t *, void *);
 extern unsigned int kmem_cache_size(kmem_cache_t *);