diff options
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/slob.c | 422 |
1 files changed, 325 insertions, 97 deletions
@@ -7,53 +7,148 @@ * * The core of SLOB is a traditional K&R style heap allocator, with * support for returning aligned objects. The granularity of this - * allocator is 8 bytes on x86, though it's perhaps possible to reduce - * this to 4 if it's deemed worth the effort. The slob heap is a - * singly-linked list of pages from __get_free_page, grown on demand - * and allocation from the heap is currently first-fit. + * allocator is 4 bytes on 32-bit and 8 bytes on 64-bit, though it + * could be as low as 2 if the compiler alignment requirements allow. + * + * The slob heap is a linked list of pages from __get_free_page, 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. * * Above this is an implementation of kmalloc/kfree. Blocks returned - * from kmalloc are 8-byte aligned and prepended with a 8-byte header. + * from kmalloc are 4-byte aligned and prepended with a 4-byte header. * If kmalloc is asked for objects of PAGE_SIZE or larger, it calls * __get_free_pages directly so that it can return page-aligned blocks * and keeps a linked list of such pages and their orders. These * objects are detected in kfree() by their page alignment. * * SLAB is emulated on top of SLOB by simply calling constructors and - * destructors for every SLAB allocation. Objects are returned with - * the 8-byte alignment unless the SLAB_HWCACHE_ALIGN flag is - * set, in which case the low-level allocator will fragment blocks to - * create the proper alignment. Again, objects of page-size or greater - * are allocated by calling __get_free_pages. As SLAB objects know - * their size, no separate size bookkeeping is necessary and there is - * essentially no allocation space overhead. + * destructors for every SLAB allocation. Objects are returned with the + * 4-byte alignment unless the SLAB_HWCACHE_ALIGN flag is set, in which + * case the low-level allocator will fragment blocks to create the proper + * alignment. Again, objects of page-size or greater are allocated by + * calling __get_free_pages. As SLAB objects know their size, no separate + * size bookkeeping is necessary and there is essentially no allocation + * space overhead. */ +#include <linux/kernel.h> #include <linux/slab.h> #include <linux/mm.h> #include <linux/cache.h> #include <linux/init.h> #include <linux/module.h> -#include <linux/timer.h> #include <linux/rcupdate.h> +#include <linux/list.h> +#include <asm/atomic.h> + +/* SLOB_MIN_ALIGN == sizeof(long) */ +#if BITS_PER_BYTE == 32 +#define SLOB_MIN_ALIGN 4 +#else +#define SLOB_MIN_ALIGN 8 +#endif +/* + * slob_block has a field 'units', which indicates size of block if +ve, + * or offset of next block if -ve (in SLOB_UNITs). + * + * Free blocks of size 1 unit simply contain the offset of the next block. + * Those with larger size contain their size in the first SLOB_UNIT of + * memory, and the offset of the next free block in the second SLOB_UNIT. + */ +#if PAGE_SIZE <= (32767 * SLOB_MIN_ALIGN) +typedef s16 slobidx_t; +#else +typedef s32 slobidx_t; +#endif + +/* + * Align struct slob_block to long for now, but can some embedded + * architectures get away with less? + */ struct slob_block { - int units; - struct slob_block *next; -}; + slobidx_t units; +} __attribute__((aligned(SLOB_MIN_ALIGN))); typedef struct slob_block slob_t; +/* + * We use struct page fields to manage some slob allocation aspects, + * however to avoid the horrible mess in include/linux/mm_types.h, we'll + * just define our own struct page type variant here. + */ +struct slob_page { + union { + struct { + unsigned long flags; /* mandatory */ + atomic_t _count; /* mandatory */ + slobidx_t units; /* free units left in page */ + unsigned long pad[2]; + slob_t *free; /* first free slob_t in page */ + struct list_head list; /* linked list of free pages */ + }; + struct page page; + }; +}; +static inline void struct_slob_page_wrong_size(void) +{ BUILD_BUG_ON(sizeof(struct slob_page) != sizeof(struct page)); } + +/* + * free_slob_page: call before a slob_page is returned to the page allocator. + */ +static inline void free_slob_page(struct slob_page *sp) +{ + reset_page_mapcount(&sp->page); + sp->page.mapping = NULL; +} + +/* + * All (partially) free slob pages go on this list. + */ +static LIST_HEAD(free_slob_pages); + +/* + * slob_page: True for all slob pages (false for bigblock pages) + */ +static inline int slob_page(struct slob_page *sp) +{ + return test_bit(PG_active, &sp->flags); +} + +static inline void set_slob_page(struct slob_page *sp) +{ + __set_bit(PG_active, &sp->flags); +} + +static inline void clear_slob_page(struct slob_page *sp) +{ + __clear_bit(PG_active, &sp->flags); +} + +/* + * slob_page_free: true for pages on free_slob_pages list. + */ +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) +{ + list_add(&sp->list, &free_slob_pages); + __set_bit(PG_private, &sp->flags); +} + +static inline void clear_slob_page_free(struct slob_page *sp) +{ + list_del(&sp->list); + __clear_bit(PG_private, &sp->flags); +} + #define SLOB_UNIT sizeof(slob_t) #define SLOB_UNITS(size) (((size) + SLOB_UNIT - 1)/SLOB_UNIT) #define SLOB_ALIGN L1_CACHE_BYTES -struct bigblock { - int order; - void *pages; - struct bigblock *next; -}; -typedef struct bigblock bigblock_t; - /* * struct slob_rcu is inserted at the tail of allocated slob blocks, which * were created with a SLAB_DESTROY_BY_RCU slab. slob_rcu is used to free @@ -64,103 +159,240 @@ struct slob_rcu { int size; }; -static slob_t arena = { .next = &arena, .units = 1 }; -static slob_t *slobfree = &arena; -static bigblock_t *bigblocks; +/* + * slob_lock protects all slob allocator structures. + */ static DEFINE_SPINLOCK(slob_lock); -static DEFINE_SPINLOCK(block_lock); -static void slob_free(void *b, int size); -static void slob_timer_cbk(void); +/* + * Encode the given size and next info into a free slob block s. + */ +static void set_slob(slob_t *s, slobidx_t size, slob_t *next) +{ + slob_t *base = (slob_t *)((unsigned long)s & PAGE_MASK); + slobidx_t offset = next - base; + if (size > 1) { + s[0].units = size; + s[1].units = offset; + } else + s[0].units = -offset; +} -static void *slob_alloc(size_t size, gfp_t gfp, int align) +/* + * Return the size of a slob block. + */ +static slobidx_t slob_units(slob_t *s) +{ + if (s->units > 0) + return s->units; + return 1; +} + +/* + * Return the next free slob block pointer after this one. + */ +static slob_t *slob_next(slob_t *s) +{ + slob_t *base = (slob_t *)((unsigned long)s & PAGE_MASK); + slobidx_t next; + + if (s[0].units < 0) + next = -s[0].units; + else + next = s[1].units; + return base+next; +} + +/* + * Returns true if s is the last free block in its page. + */ +static int slob_last(slob_t *s) +{ + return !((unsigned long)slob_next(s) & ~PAGE_MASK); +} + +/* + * Allocate a slob block within a given slob_page sp. + */ +static void *slob_page_alloc(struct slob_page *sp, size_t size, int align) { slob_t *prev, *cur, *aligned = 0; int delta = 0, units = SLOB_UNITS(size); - unsigned long flags; - spin_lock_irqsave(&slob_lock, flags); - prev = slobfree; - for (cur = prev->next; ; prev = cur, cur = cur->next) { + for (prev = NULL, cur = sp->free; ; prev = cur, cur = slob_next(cur)) { + slobidx_t avail = slob_units(cur); + if (align) { aligned = (slob_t *)ALIGN((unsigned long)cur, align); delta = aligned - cur; } - if (cur->units >= units + delta) { /* room enough? */ + if (avail >= units + delta) { /* room enough? */ + slob_t *next; + if (delta) { /* need to fragment head to align? */ - aligned->units = cur->units - delta; - aligned->next = cur->next; - cur->next = aligned; - cur->units = delta; + next = slob_next(cur); + set_slob(aligned, avail - delta, next); + set_slob(cur, delta, aligned); prev = cur; cur = aligned; + avail = slob_units(cur); } - if (cur->units == units) /* exact fit? */ - prev->next = cur->next; /* unlink */ - else { /* fragment */ - prev->next = cur + units; - prev->next->units = cur->units - units; - prev->next->next = cur->next; - cur->units = units; + next = slob_next(cur); + if (avail == units) { /* exact fit? unlink. */ + if (prev) + set_slob(prev, slob_units(prev), next); + else + sp->free = next; + } else { /* fragment */ + if (prev) + set_slob(prev, slob_units(prev), cur + units); + else + sp->free = cur + units; + set_slob(cur + units, avail - units, next); } - slobfree = prev; - spin_unlock_irqrestore(&slob_lock, flags); + sp->units -= units; + if (!sp->units) + clear_slob_page_free(sp); return cur; } - if (cur == slobfree) { - spin_unlock_irqrestore(&slob_lock, flags); - - if (size == PAGE_SIZE) /* trying to shrink arena? */ - return 0; + if (slob_last(cur)) + return NULL; + } +} - cur = (slob_t *)__get_free_page(gfp); - if (!cur) - return 0; +/* + * slob_alloc: entry point into the slob allocator. + */ +static void *slob_alloc(size_t size, gfp_t gfp, int align) +{ + struct slob_page *sp; + slob_t *b = NULL; + unsigned long flags; - slob_free(cur, PAGE_SIZE); - spin_lock_irqsave(&slob_lock, flags); - cur = slobfree; + 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) { + if (sp->units >= SLOB_UNITS(size)) { + b = slob_page_alloc(sp, size, align); + if (b) + break; } } + spin_unlock_irqrestore(&slob_lock, flags); + + /* Not enough space: must allocate a new page */ + if (!b) { + b = (slob_t *)__get_free_page(gfp); + if (!b) + return 0; + sp = (struct slob_page *)virt_to_page(b); + set_slob_page(sp); + + spin_lock_irqsave(&slob_lock, flags); + sp->units = SLOB_UNITS(PAGE_SIZE); + 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); + b = slob_page_alloc(sp, size, align); + BUG_ON(!b); + spin_unlock_irqrestore(&slob_lock, flags); + } + return b; } +/* + * slob_free: entry point into the slob allocator. + */ static void slob_free(void *block, int size) { - slob_t *cur, *b = (slob_t *)block; + struct slob_page *sp; + slob_t *prev, *next, *b = (slob_t *)block; + slobidx_t units; unsigned long flags; if (!block) return; + BUG_ON(!size); - if (size) - b->units = SLOB_UNITS(size); + sp = (struct slob_page *)virt_to_page(block); + units = SLOB_UNITS(size); - /* Find reinsertion point */ spin_lock_irqsave(&slob_lock, flags); - for (cur = slobfree; !(b > cur && b < cur->next); cur = cur->next) - if (cur >= cur->next && (b > cur || b < cur->next)) - break; - if (b + b->units == cur->next) { - b->units += cur->next->units; - b->next = cur->next->next; - } else - b->next = cur->next; + if (sp->units + units == SLOB_UNITS(PAGE_SIZE)) { + /* Go directly to page allocator. Do not pass slob allocator */ + if (slob_page_free(sp)) + clear_slob_page_free(sp); + clear_slob_page(sp); + free_slob_page(sp); + free_page((unsigned long)b); + goto out; + } - if (cur + cur->units == b) { - cur->units += b->units; - cur->next = b->next; - } else - cur->next = b; + if (!slob_page_free(sp)) { + /* This slob page is about to become partially free. Easy! */ + sp->units = units; + sp->free = b; + set_slob(b, units, + (void *)((unsigned long)(b + + SLOB_UNITS(PAGE_SIZE)) & PAGE_MASK)); + set_slob_page_free(sp); + goto out; + } + + /* + * Otherwise the page is already partially free, so find reinsertion + * point. + */ + sp->units += units; - slobfree = cur; + if (b < sp->free) { + set_slob(b, units, sp->free); + sp->free = b; + } else { + prev = sp->free; + next = slob_next(prev); + while (b > next) { + prev = next; + next = slob_next(prev); + } + if (!slob_last(prev) && b + units == next) { + units += slob_units(next); + set_slob(b, units, slob_next(next)); + } else + set_slob(b, units, next); + + if (prev + slob_units(prev) == b) { + units = slob_units(b) + slob_units(prev); + set_slob(prev, units, slob_next(b)); + } else + set_slob(prev, slob_units(prev), b); + } +out: spin_unlock_irqrestore(&slob_lock, flags); } +/* + * End of slob allocator proper. Begin kmem_cache_alloc and kmalloc frontend. + */ + +struct bigblock { + int order; + void *pages; + struct bigblock *next; +}; +typedef struct bigblock bigblock_t; + +static bigblock_t *bigblocks; + +static DEFINE_SPINLOCK(block_lock); + + void *__kmalloc(size_t size, gfp_t gfp) { slob_t *m; @@ -169,7 +401,9 @@ void *__kmalloc(size_t size, gfp_t gfp) if (size < PAGE_SIZE - SLOB_UNIT) { m = slob_alloc(size + SLOB_UNIT, gfp, 0); - return m ? (void *)(m + 1) : 0; + if (m) + m->units = size; + return m+1; } bb = slob_alloc(sizeof(bigblock_t), gfp, 0); @@ -227,14 +461,17 @@ EXPORT_SYMBOL(krealloc); void kfree(const void *block) { + struct slob_page *sp; + slob_t *m; bigblock_t *bb, **last = &bigblocks; unsigned long flags; if (!block) return; - if (!((unsigned long)block & (PAGE_SIZE-1))) { - /* might be on the big block list */ + sp = (struct slob_page *)virt_to_page(block); + if (!slob_page(sp)) { + /* on the big block list */ spin_lock_irqsave(&block_lock, flags); for (bb = bigblocks; bb; last = &bb->next, bb = bb->next) { if (bb->pages == block) { @@ -246,9 +483,12 @@ void kfree(const void *block) } } spin_unlock_irqrestore(&block_lock, flags); + WARN_ON(1); + return; } - slob_free((slob_t *)block - 1, 0); + m = (slob_t *)block - 1; + slob_free(m, m->units + SLOB_UNIT); return; } @@ -256,13 +496,15 @@ EXPORT_SYMBOL(kfree); size_t ksize(const void *block) { + struct slob_page *sp; bigblock_t *bb; unsigned long flags; if (!block) return 0; - if (!((unsigned long)block & (PAGE_SIZE-1))) { + sp = (struct slob_page *)virt_to_page(block); + if (!slob_page(sp)) { spin_lock_irqsave(&block_lock, flags); for (bb = bigblocks; bb; bb = bb->next) if (bb->pages == block) { @@ -272,7 +514,7 @@ size_t ksize(const void *block) spin_unlock_irqrestore(&block_lock, flags); } - return ((slob_t *)block - 1)->units * SLOB_UNIT; + return ((slob_t *)block - 1)->units + SLOB_UNIT; } struct kmem_cache { @@ -385,9 +627,6 @@ const char *kmem_cache_name(struct kmem_cache *c) } EXPORT_SYMBOL(kmem_cache_name); -static struct timer_list slob_timer = TIMER_INITIALIZER( - (void (*)(unsigned long))slob_timer_cbk, 0, 0); - int kmem_cache_shrink(struct kmem_cache *d) { return 0; @@ -401,15 +640,4 @@ int kmem_ptr_validate(struct kmem_cache *a, const void *b) void __init kmem_cache_init(void) { - slob_timer_cbk(); -} - -static void slob_timer_cbk(void) -{ - void *p = slob_alloc(PAGE_SIZE, 0, PAGE_SIZE-1); - - if (p) - free_page((unsigned long)p); - - mod_timer(&slob_timer, jiffies + HZ); } |