[PATCH] sched: improve efficiency of sched_fork()

[powerpc.git] / mm / slab.c

diff --git a/mm/slab.c b/mm/slab.c
index 9d35500..909975f 100644 (file)
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -109,6 +109,7 @@
 #include       <linux/mutex.h>
 #include       <linux/fault-inject.h>
 #include       <linux/rtmutex.h>
+#include       <linux/reciprocal_div.h>
 
 #include       <asm/cacheflush.h>
 #include       <asm/tlbflush.h>
@@ -386,6 +387,7 @@ struct kmem_cache {
        unsigned int shared;
 
        unsigned int buffer_size;
+       u32 reciprocal_buffer_size;
 /* 3) touched by every alloc & free from the backend */
        struct kmem_list3 *nodelists[MAX_NUMNODES];
 
@@ -627,10 +629,17 @@ static inline void *index_to_obj(struct kmem_cache *cache, struct slab *slab,
        return slab->s_mem + cache->buffer_size * idx;
 }
 
-static inline unsigned int obj_to_index(struct kmem_cache *cache,
-                                       struct slab *slab, void *obj)
+/*
+ * We want to avoid an expensive divide : (offset / cache->buffer_size)
+ *   Using the fact that buffer_size is a constant for a particular cache,
+ *   we can replace (offset / cache->buffer_size) by
+ *   reciprocal_divide(offset, cache->reciprocal_buffer_size)
+ */
+static inline unsigned int obj_to_index(const struct kmem_cache *cache,
+                                       const struct slab *slab, void *obj)
 {
-       return (unsigned)(obj - slab->s_mem) / cache->buffer_size;
+       u32 offset = (obj - slab->s_mem);
+       return reciprocal_divide(offset, cache->reciprocal_buffer_size);
 }
 
 /*
@@ -1427,6 +1436,8 @@ void __init kmem_cache_init(void)
 
        cache_cache.buffer_size = ALIGN(cache_cache.buffer_size,
                                        cache_line_size());
+       cache_cache.reciprocal_buffer_size =
+               reciprocal_value(cache_cache.buffer_size);
 
        for (order = 0; order < MAX_ORDER; order++) {
                cache_estimate(order, cache_cache.buffer_size,
@@ -2313,6 +2324,7 @@ kmem_cache_create (const char *name, size_t size, size_t align,
        if (flags & SLAB_CACHE_DMA)
                cachep->gfpflags |= GFP_DMA;
        cachep->buffer_size = size;
+       cachep->reciprocal_buffer_size = reciprocal_value(size);
 
        if (flags & CFLGS_OFF_SLAB) {
                cachep->slabp_cache = kmem_find_general_cachep(slab_size, 0u);
@@ -3262,7 +3274,7 @@ retry:
        for (z = zonelist->zones; *z && !obj; z++) {
                nid = zone_to_nid(*z);
 
-               if (cpuset_zone_allowed(*z, flags | __GFP_HARDWALL) &&
+               if (cpuset_zone_allowed_hardwall(*z, flags) &&
                        cache->nodelists[nid] &&
                        cache->nodelists[nid]->free_objects)
                                obj = ____cache_alloc_node(cache,