slub: Determine gfpflags once and not every time a slab is allocated

Currently we determine the gfp flags to pass to the page allocator
each time a slab is being allocated.

Determine the bits to be set at the time the slab is created. Store
in a new allocflags field and add the flags in allocate_slab().
Acked-by: NMel Gorman <mel@csn.ul.ie>
Reviewed-by: NPekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: NChristoph Lameter <clameter@sgi.com>

include/linux/slub_def.h

@@ -71,6 +71,7 @@ struct kmem_cache {
 
 	/* Allocation and freeing of slabs */
 	int objects;		/* Number of objects in slab */
+	gfp_t allocflags;	/* gfp flags to use on each alloc */
 	int refcount;		/* Refcount for slab cache destroy */
 	void (*ctor)(struct kmem_cache *, void *);
 	int inuse;		/* Offset to metadata */

mm/slub.c

@@ -1078,14 +1078,7 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 	struct page *page;
 	int pages = 1 << s->order;
 
-	if (s->order)
-		flags |= __GFP_COMP;
-
-	if (s->flags & SLAB_CACHE_DMA)
-		flags |= SLUB_DMA;
-
-	if (s->flags & SLAB_RECLAIM_ACCOUNT)
-		flags |= __GFP_RECLAIMABLE;
+	flags |= s->allocflags;
 
 	if (node == -1)
 		page = alloc_pages(flags, s->order);
@@ -2333,6 +2326,16 @@ static int calculate_sizes(struct kmem_cache *s)
 	if (s->order < 0)
 		return 0;
 
+	s->allocflags = 0;
+	if (s->order)
+		s->allocflags |= __GFP_COMP;
+
+	if (s->flags & SLAB_CACHE_DMA)
+		s->allocflags |= SLUB_DMA;
+
+	if (s->flags & SLAB_RECLAIM_ACCOUNT)
+		s->allocflags |= __GFP_RECLAIMABLE;
+
 	/*
 	 * Determine the number of objects per slab
 	 */