1 files changed, 33 insertions, 14 deletions

diff --git a/mm/slob.c b/mm/slob.c
index c56c5e57c192..e2c3c0ec5463 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -12,10 +12,17 @@
  * allocator is as little as 2 bytes, however typically most architectures
  * will require 4 bytes on 32-bit and 8 bytes on 64-bit.
  *
- * The slob heap is a linked list of pages from alloc_pages(), and
- * within each page, there is a singly-linked list of free blocks (slob_t).
- * The heap is grown on demand and allocation from the heap is currently
- * first-fit.
+ * The slob heap is a set of linked list of pages from alloc_pages(),
+ * and within each page, there is a singly-linked list of free blocks
+ * (slob_t). The heap is grown on demand. To reduce fragmentation,
+ * heap pages are segregated into three lists, with objects less than
+ * 256 bytes, objects less than 1024 bytes, and all other objects.
+ *
+ * Allocation from heap involves first searching for a page with
+ * sufficient free blocks (using a next-fit-like approach) followed by
+ * a first-fit scan of the page. Deallocation inserts objects back
+ * into the free list in address order, so this is effectively an
+ * address-ordered first fit.
  *
  * Above this is an implementation of kmalloc/kfree. Blocks returned
  * from kmalloc are prepended with a 4-byte header with the kmalloc size.
@@ -110,9 +117,13 @@ static inline void free_slob_page(struct slob_page *sp)
 }
 
 /*
- * All (partially) free slob pages go on this list.
+ * All partially free slob pages go on these lists.
  */
-static LIST_HEAD(free_slob_pages);
+#define SLOB_BREAK1 256
+#define SLOB_BREAK2 1024
+static LIST_HEAD(free_slob_small);
+static LIST_HEAD(free_slob_medium);
+static LIST_HEAD(free_slob_large);
 
 /*
  * slob_page: True for all slob pages (false for bigblock pages)
@@ -140,9 +151,9 @@ static inline int slob_page_free(struct slob_page *sp)
         return test_bit(PG_private, &sp->flags);
 }
 
-static inline void set_slob_page_free(struct slob_page *sp)
+static void set_slob_page_free(struct slob_page *sp, struct list_head *list)
 {
-        list_add(&sp->list, &free_slob_pages);
+        list_add(&sp->list, list);
         __set_bit(PG_private, &sp->flags);
 }
 
@@ -294,12 +305,20 @@ static void *slob_alloc(size_t size, gfp_t gfp, int align, int node)
 {
         struct slob_page *sp;
         struct list_head *prev;
+        struct list_head *slob_list;
         slob_t *b = NULL;
         unsigned long flags;
 
+        if (size < SLOB_BREAK1)
+                slob_list = &free_slob_small;
+        else if (size < SLOB_BREAK2)
+                slob_list = &free_slob_medium;
+        else
+                slob_list = &free_slob_large;
+
         spin_lock_irqsave(&slob_lock, flags);
         /* Iterate through each partially free page, try to find room */
-        list_for_each_entry(sp, &free_slob_pages, list) {
+        list_for_each_entry(sp, slob_list, list) {
 #ifdef CONFIG_NUMA
                 /*
                  * If there's a node specification, search for a partial
@@ -321,9 +340,9 @@ static void *slob_alloc(size_t size, gfp_t gfp, int align, int node)
                 /* Improve fragment distribution and reduce our average
                  * search time by starting our next search here. (see
                  * Knuth vol 1, sec 2.5, pg 449) */
-                if (prev != free_slob_pages.prev &&
-                                free_slob_pages.next != prev->next)
-                        list_move_tail(&free_slob_pages, prev->next);
+                if (prev != slob_list->prev &&
+                                slob_list->next != prev->next)
+                        list_move_tail(slob_list, prev->next);
                 break;
         }
         spin_unlock_irqrestore(&slob_lock, flags);
@@ -341,7 +360,7 @@ static void *slob_alloc(size_t size, gfp_t gfp, int align, int node)
                 sp->free = b;
                 INIT_LIST_HEAD(&sp->list);
                 set_slob(b, SLOB_UNITS(PAGE_SIZE), b + SLOB_UNITS(PAGE_SIZE));
-                set_slob_page_free(sp);
+                set_slob_page_free(sp, slob_list);
                 b = slob_page_alloc(sp, size, align);
                 BUG_ON(!b);
                 spin_unlock_irqrestore(&slob_lock, flags);
@@ -387,7 +406,7 @@ static void slob_free(void *block, int size)
                 set_slob(b, units,
                         (void *)((unsigned long)(b +
                                         SLOB_UNITS(PAGE_SIZE)) & PAGE_MASK));
-                set_slob_page_free(sp);
+                set_slob_page_free(sp, &free_slob_small);
                 goto out;
         }