diff options
| -rw-r--r-- | mm/slob.c | 47 |
1 files changed, 33 insertions, 14 deletions
@@ -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; } |
