SLUB: Introduce and use SLUB_MAX_SIZE and SLUB_PAGE_SHIFT constants

As a preparational patch to bump up page allocator pass-through threshold,
introduce two new constants SLUB_MAX_SIZE and SLUB_PAGE_SHIFT and convert
mm/slub.c to use them.

Reported-by: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>
Tested-by: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>

diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index 2f5c16b1aacd3d7bd83a50d90fcba527017a0373..986e09dcfd8f52255612af7dfb2b8b5318616aec 100644 (file)
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -120,11 +120,24 @@ struct kmem_cache {
 
 #define KMALLOC_SHIFT_LOW ilog2(KMALLOC_MIN_SIZE)
 
+/*
+ * Maximum kmalloc object size handled by SLUB. Larger object allocations
+ * are passed through to the page allocator. The page allocator "fastpath"
+ * is relatively slow so we need this value sufficiently high so that
+ * performance critical objects are allocated through the SLUB fastpath.
+ *
+ * This should be dropped to PAGE_SIZE / 2 once the page allocator
+ * "fastpath" becomes competitive with the slab allocator fastpaths.
+ */
+#define SLUB_MAX_SIZE (PAGE_SIZE)
+
+#define SLUB_PAGE_SHIFT (PAGE_SHIFT + 1)
+
 /*
  * We keep the general caches in an array of slab caches that are used for
  * 2^x bytes of allocations.
  */
-extern struct kmem_cache kmalloc_caches[PAGE_SHIFT + 1];
+extern struct kmem_cache kmalloc_caches[SLUB_PAGE_SHIFT];
 
 /*
  * Sorry that the following has to be that ugly but some versions of GCC
@@ -212,7 +225,7 @@ static __always_inline void *kmalloc_large(size_t size, gfp_t flags)
 static __always_inline void *kmalloc(size_t size, gfp_t flags)
 {
        if (__builtin_constant_p(size)) {
-               if (size > PAGE_SIZE)
+               if (size > SLUB_MAX_SIZE)
                        return kmalloc_large(size, flags);
 
                if (!(flags & SLUB_DMA)) {
@@ -234,7 +247,7 @@ void *kmem_cache_alloc_node(struct kmem_cache *, gfp_t flags, int node);
 static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
 {
        if (__builtin_constant_p(size) &&
-               size <= PAGE_SIZE && !(flags & SLUB_DMA)) {
+               size <= SLUB_MAX_SIZE && !(flags & SLUB_DMA)) {
                        struct kmem_cache *s = kmalloc_slab(size);
 
                if (!s)

diff --git a/mm/slub.c b/mm/slub.c
index bdc9abb08a230f2724ad842a0bc4928da0e48d23..5a5e7f5bf79935ccde6b21fc9da49870f15a11ba 100644 (file)
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2475,7 +2475,7 @@ EXPORT_SYMBOL(kmem_cache_destroy);
  *             Kmalloc subsystem
  *******************************************************************/
 
-struct kmem_cache kmalloc_caches[PAGE_SHIFT + 1] __cacheline_aligned;
+struct kmem_cache kmalloc_caches[SLUB_PAGE_SHIFT] __cacheline_aligned;
 EXPORT_SYMBOL(kmalloc_caches);
 
 static int __init setup_slub_min_order(char *str)
@@ -2537,7 +2537,7 @@ panic:
 }
 
 #ifdef CONFIG_ZONE_DMA
-static struct kmem_cache *kmalloc_caches_dma[PAGE_SHIFT + 1];
+static struct kmem_cache *kmalloc_caches_dma[SLUB_PAGE_SHIFT];
 
 static void sysfs_add_func(struct work_struct *w)
 {
@@ -2658,7 +2658,7 @@ void *__kmalloc(size_t size, gfp_t flags)
 {
        struct kmem_cache *s;
 
-       if (unlikely(size > PAGE_SIZE))
+       if (unlikely(size > SLUB_MAX_SIZE))
                return kmalloc_large(size, flags);
 
        s = get_slab(size, flags);
@@ -2686,7 +2686,7 @@ void *__kmalloc_node(size_t size, gfp_t flags, int node)
 {
        struct kmem_cache *s;
 
-       if (unlikely(size > PAGE_SIZE))
+       if (unlikely(size > SLUB_MAX_SIZE))
                return kmalloc_large_node(size, flags, node);
 
        s = get_slab(size, flags);
@@ -2985,7 +2985,7 @@ void __init kmem_cache_init(void)
                caches++;
        }
 
-       for (i = KMALLOC_SHIFT_LOW; i <= PAGE_SHIFT; i++) {
+       for (i = KMALLOC_SHIFT_LOW; i < SLUB_PAGE_SHIFT; i++) {
                create_kmalloc_cache(&kmalloc_caches[i],
                        "kmalloc", 1 << i, GFP_KERNEL);
                caches++;
@@ -3022,7 +3022,7 @@ void __init kmem_cache_init(void)
        slab_state = UP;
 
        /* Provide the correct kmalloc names now that the caches are up */
-       for (i = KMALLOC_SHIFT_LOW; i <= PAGE_SHIFT; i++)
+       for (i = KMALLOC_SHIFT_LOW; i < SLUB_PAGE_SHIFT; i++)
                kmalloc_caches[i]. name =
                        kasprintf(GFP_KERNEL, "kmalloc-%d", 1 << i);
 
@@ -3222,7 +3222,7 @@ void *__kmalloc_track_caller(size_t size, gfp_t gfpflags, unsigned long caller)
 {
        struct kmem_cache *s;
 
-       if (unlikely(size > PAGE_SIZE))
+       if (unlikely(size > SLUB_MAX_SIZE))
                return kmalloc_large(size, gfpflags);
 
        s = get_slab(size, gfpflags);
@@ -3238,7 +3238,7 @@ void *__kmalloc_node_track_caller(size_t size, gfp_t gfpflags,
 {
        struct kmem_cache *s;
 
-       if (unlikely(size > PAGE_SIZE))
+       if (unlikely(size > SLUB_MAX_SIZE))
                return kmalloc_large_node(size, gfpflags, node);
 
        s = get_slab(size, gfpflags);