mm/slob.c - linux - Git at Google

 /*
  * SLOB Allocator: Simple List Of Blocks
  *
  * Matt Mackall <mpm@selenic.com> 12/30/03
  *
  * How SLOB works:
  *
  * 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.
  *
  * Above this is an implementation of kmalloc/kfree. Blocks returned
  * from kmalloc are 8-byte aligned and prepended with a 8-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_MUST_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/slab.h>
 #include <linux/mm.h>
 #include <linux/cache.h>
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/timer.h>

 struct slob_block {
 	int units;
 	struct slob_block *next;
 };
 typedef struct slob_block slob_t;

 #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;

 static slob_t arena = { .next = &arena, .units = 1 };
 static slob_t *slobfree = &arena;
 static bigblock_t *bigblocks;
 static DEFINE_SPINLOCK(slob_lock);
 static DEFINE_SPINLOCK(block_lock);

 static void slob_free(void *b, int size);

 static void *slob_alloc(size_t size, gfp_t gfp, 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) {
 		if (align) {
 			aligned = (slob_t *)ALIGN((unsigned long)cur, align);
 			delta = aligned - cur;
 		}
 		if (cur->units >= units + delta) { /* room enough? */
 			if (delta) { /* need to fragment head to align? */
 				aligned->units = cur->units - delta;
 				aligned->next = cur->next;
 				cur->next = aligned;
 				cur->units = delta;
 				prev = cur;
 				cur = aligned;
 			}

 			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;
 			}

 			slobfree = prev;
 			spin_unlock_irqrestore(&slob_lock, flags);
 			return cur;
 		}
 		if (cur == slobfree) {
 			spin_unlock_irqrestore(&slob_lock, flags);

 			if (size == PAGE_SIZE) /* trying to shrink arena? */
 				return 0;

 			cur = (slob_t *)__get_free_page(gfp);
 			if (!cur)
 				return 0;

 			slob_free(cur, PAGE_SIZE);
 			spin_lock_irqsave(&slob_lock, flags);
 			cur = slobfree;
 		}
 	}
 }

 static void slob_free(void *block, int size)
 {
 	slob_t *cur, *b = (slob_t *)block;
 	unsigned long flags;

 	if (!block)
 		return;

 	if (size)
 		b->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 (cur + cur->units == b) {
 		cur->units += b->units;
 		cur->next = b->next;
 	} else
 		cur->next = b;

 	slobfree = cur;

 	spin_unlock_irqrestore(&slob_lock, flags);
 }

 static int FASTCALL(find_order(int size));
 static int fastcall find_order(int size)
 {
 	int order = 0;
 	for ( ; size > 4096 ; size >>=1)
 		order++;
 	return order;
 }

 void *kmalloc(size_t size, gfp_t gfp)
 {
 	slob_t *m;
 	bigblock_t *bb;
 	unsigned long flags;

 	if (size < PAGE_SIZE - SLOB_UNIT) {
 		m = slob_alloc(size + SLOB_UNIT, gfp, 0);
 		return m ? (void *)(m + 1) : 0;
 	}

 	bb = slob_alloc(sizeof(bigblock_t), gfp, 0);
 	if (!bb)
 		return 0;

 	bb->order = find_order(size);
 	bb->pages = (void *)__get_free_pages(gfp, bb->order);

 	if (bb->pages) {
 		spin_lock_irqsave(&block_lock, flags);
 		bb->next = bigblocks;
 		bigblocks = bb;
 		spin_unlock_irqrestore(&block_lock, flags);
 		return bb->pages;
 	}

 	slob_free(bb, sizeof(bigblock_t));
 	return 0;
 }

 EXPORT_SYMBOL(kmalloc);

 void kfree(const void *block)
 {
 	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 */
 		spin_lock_irqsave(&block_lock, flags);
 		for (bb = bigblocks; bb; last = &bb->next, bb = bb->next) {
 			if (bb->pages == block) {
 				*last = bb->next;
 				spin_unlock_irqrestore(&block_lock, flags);
 				free_pages((unsigned long)block, bb->order);
 				slob_free(bb, sizeof(bigblock_t));
 				return;
 			}
 		}
 		spin_unlock_irqrestore(&block_lock, flags);
 	}

 	slob_free((slob_t *)block - 1, 0);
 	return;
 }

 EXPORT_SYMBOL(kfree);

 unsigned int ksize(const void *block)
 {
 	bigblock_t *bb;
 	unsigned long flags;

 	if (!block)
 		return 0;

 	if (!((unsigned long)block & (PAGE_SIZE-1))) {
 		spin_lock_irqsave(&block_lock, flags);
 		for (bb = bigblocks; bb; bb = bb->next)
 			if (bb->pages == block) {
 				spin_unlock_irqrestore(&slob_lock, flags);
 				return PAGE_SIZE << bb->order;
 			}
 		spin_unlock_irqrestore(&block_lock, flags);
 	}

 	return ((slob_t *)block - 1)->units * SLOB_UNIT;
 }

 struct kmem_cache {
 	unsigned int size, align;
 	const char *name;
 	void (*ctor)(void *, struct kmem_cache *, unsigned long);
 	void (*dtor)(void *, struct kmem_cache *, unsigned long);
 };

 struct kmem_cache *kmem_cache_create(const char *name, size_t size,
 	size_t align, unsigned long flags,
 	void (*ctor)(void*, struct kmem_cache *, unsigned long),
 	void (*dtor)(void*, struct kmem_cache *, unsigned long))
 {
 	struct kmem_cache *c;

 	c = slob_alloc(sizeof(struct kmem_cache), flags, 0);

 	if (c) {
 		c->name = name;
 		c->size = size;
 		c->ctor = ctor;
 		c->dtor = dtor;
 		/* ignore alignment unless it's forced */
 		c->align = (flags & SLAB_MUST_HWCACHE_ALIGN) ? SLOB_ALIGN : 0;
 		if (c->align < align)
 			c->align = align;
 	}

 	return c;
 }
 EXPORT_SYMBOL(kmem_cache_create);

 int kmem_cache_destroy(struct kmem_cache *c)
 {
 	slob_free(c, sizeof(struct kmem_cache));
 	return 0;
 }
 EXPORT_SYMBOL(kmem_cache_destroy);

 void *kmem_cache_alloc(struct kmem_cache *c, gfp_t flags)
 {
 	void *b;

 	if (c->size < PAGE_SIZE)
 		b = slob_alloc(c->size, flags, c->align);
 	else
 		b = (void *)__get_free_pages(flags, find_order(c->size));

 	if (c->ctor)
 		c->ctor(b, c, SLAB_CTOR_CONSTRUCTOR);

 	return b;
 }
 EXPORT_SYMBOL(kmem_cache_alloc);

 void *kmem_cache_zalloc(struct kmem_cache *c, gfp_t flags)
 {
 	void *ret = kmem_cache_alloc(c, flags);
 	if (ret)
 		memset(ret, 0, c->size);

 	return ret;
 }
 EXPORT_SYMBOL(kmem_cache_zalloc);

 void kmem_cache_free(struct kmem_cache *c, void *b)
 {
 	if (c->dtor)
 		c->dtor(b, c, 0);

 	if (c->size < PAGE_SIZE)
 		slob_free(b, c->size);
 	else
 		free_pages((unsigned long)b, find_order(c->size));
 }
 EXPORT_SYMBOL(kmem_cache_free);

 unsigned int kmem_cache_size(struct kmem_cache *c)
 {
 	return c->size;
 }
 EXPORT_SYMBOL(kmem_cache_size);

 const char *kmem_cache_name(struct kmem_cache *c)
 {
 	return c->name;
 }
 EXPORT_SYMBOL(kmem_cache_name);

 static struct timer_list slob_timer = TIMER_INITIALIZER(
 	(void (*)(unsigned long))kmem_cache_init, 0, 0);

 void kmem_cache_init(void)
 {
 	void *p = slob_alloc(PAGE_SIZE, 0, PAGE_SIZE-1);

 	if (p)
 		free_page((unsigned long)p);

 	mod_timer(&slob_timer, jiffies + HZ);
 }

 atomic_t slab_reclaim_pages = ATOMIC_INIT(0);
 EXPORT_SYMBOL(slab_reclaim_pages);

 #ifdef CONFIG_SMP

 void *__alloc_percpu(size_t size)
 {
 	int i;
 	struct percpu_data *pdata = kmalloc(sizeof (*pdata), GFP_KERNEL);

 	if (!pdata)
 		return NULL;

 	for_each_possible_cpu(i) {
 		pdata->ptrs[i] = kmalloc(size, GFP_KERNEL);
 		if (!pdata->ptrs[i])
 			goto unwind_oom;
 		memset(pdata->ptrs[i], 0, size);
 	}

 	/* Catch derefs w/o wrappers */
 	return (void *) (~(unsigned long) pdata);

 unwind_oom:
 	while (--i >= 0) {
 		if (!cpu_possible(i))
 			continue;
 		kfree(pdata->ptrs[i]);
 	}
 	kfree(pdata);
 	return NULL;
 }
 EXPORT_SYMBOL(__alloc_percpu);

 void
 free_percpu(const void *objp)
 {
 	int i;
 	struct percpu_data *p = (struct percpu_data *) (~(unsigned long) objp);

 	for_each_possible_cpu(i)
 		kfree(p->ptrs[i]);

 	kfree(p);
 }
 EXPORT_SYMBOL(free_percpu);

 #endif
	/*
	* SLOB Allocator: Simple List Of Blocks
	*
	* Matt Mackall <mpm@selenic.com> 12/30/03
	*
	* How SLOB works:
	*
	* 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.
	*
	* Above this is an implementation of kmalloc/kfree. Blocks returned
	* from kmalloc are 8-byte aligned and prepended with a 8-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_MUST_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/slab.h>
	#include <linux/mm.h>
	#include <linux/cache.h>
	#include <linux/init.h>
	#include <linux/module.h>
	#include <linux/timer.h>

	struct slob_block {
	int units;
	struct slob_block *next;
	};
	typedef struct slob_block slob_t;

	#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;

	static slob_t arena = { .next = &arena, .units = 1 };
	static slob_t *slobfree = &arena;
	static bigblock_t *bigblocks;
	static DEFINE_SPINLOCK(slob_lock);
	static DEFINE_SPINLOCK(block_lock);

	static void slob_free(void *b, int size);

	static void *slob_alloc(size_t size, gfp_t gfp, 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) {
	if (align) {
	aligned = (slob_t *)ALIGN((unsigned long)cur, align);
	delta = aligned - cur;
	}
	if (cur->units >= units + delta) { /* room enough? */
	if (delta) { /* need to fragment head to align? */
	aligned->units = cur->units - delta;
	aligned->next = cur->next;
	cur->next = aligned;
	cur->units = delta;
	prev = cur;
	cur = aligned;
	}

	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;
	}

	slobfree = prev;
	spin_unlock_irqrestore(&slob_lock, flags);
	return cur;
	}
	if (cur == slobfree) {
	spin_unlock_irqrestore(&slob_lock, flags);

	if (size == PAGE_SIZE) /* trying to shrink arena? */
	return 0;

	cur = (slob_t *)__get_free_page(gfp);
	if (!cur)
	return 0;

	slob_free(cur, PAGE_SIZE);
	spin_lock_irqsave(&slob_lock, flags);
	cur = slobfree;
	}
	}
	}

	static void slob_free(void *block, int size)
	{
	slob_t cur, b = (slob_t *)block;
	unsigned long flags;

	if (!block)
	return;

	if (size)
	b->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 (cur + cur->units == b) {
	cur->units += b->units;
	cur->next = b->next;
	} else
	cur->next = b;

	slobfree = cur;

	spin_unlock_irqrestore(&slob_lock, flags);
	}

	static int FASTCALL(find_order(int size));
	static int fastcall find_order(int size)
	{
	int order = 0;
	for ( ; size > 4096 ; size >>=1)
	order++;
	return order;
	}

	void *kmalloc(size_t size, gfp_t gfp)
	{
	slob_t *m;
	bigblock_t *bb;
	unsigned long flags;

	if (size < PAGE_SIZE - SLOB_UNIT) {
	m = slob_alloc(size + SLOB_UNIT, gfp, 0);
	return m ? (void *)(m + 1) : 0;
	}

	bb = slob_alloc(sizeof(bigblock_t), gfp, 0);
	if (!bb)
	return 0;

	bb->order = find_order(size);
	bb->pages = (void *)__get_free_pages(gfp, bb->order);

	if (bb->pages) {
	spin_lock_irqsave(&block_lock, flags);
	bb->next = bigblocks;
	bigblocks = bb;
	spin_unlock_irqrestore(&block_lock, flags);
	return bb->pages;
	}

	slob_free(bb, sizeof(bigblock_t));
	return 0;
	}

	EXPORT_SYMBOL(kmalloc);

	void kfree(const void *block)
	{
	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 */
	spin_lock_irqsave(&block_lock, flags);
	for (bb = bigblocks; bb; last = &bb->next, bb = bb->next) {
	if (bb->pages == block) {
	*last = bb->next;
	spin_unlock_irqrestore(&block_lock, flags);
	free_pages((unsigned long)block, bb->order);
	slob_free(bb, sizeof(bigblock_t));
	return;
	}
	}
	spin_unlock_irqrestore(&block_lock, flags);
	}

	slob_free((slob_t *)block - 1, 0);
	return;
	}

	EXPORT_SYMBOL(kfree);

	unsigned int ksize(const void *block)
	{
	bigblock_t *bb;
	unsigned long flags;

	if (!block)
	return 0;

	if (!((unsigned long)block & (PAGE_SIZE-1))) {
	spin_lock_irqsave(&block_lock, flags);
	for (bb = bigblocks; bb; bb = bb->next)
	if (bb->pages == block) {
	spin_unlock_irqrestore(&slob_lock, flags);
	return PAGE_SIZE << bb->order;
	}
	spin_unlock_irqrestore(&block_lock, flags);
	}

	return ((slob_t )block - 1)->units SLOB_UNIT;
	}

	struct kmem_cache {
	unsigned int size, align;
	const char *name;
	void (ctor)(void , struct kmem_cache *, unsigned long);
	void (dtor)(void , struct kmem_cache *, unsigned long);
	};

	struct kmem_cache kmem_cache_create(const char name, size_t size,
	size_t align, unsigned long flags,
	void (ctor)(void, struct kmem_cache *, unsigned long),
	void (dtor)(void, struct kmem_cache *, unsigned long))
	{
	struct kmem_cache *c;

	c = slob_alloc(sizeof(struct kmem_cache), flags, 0);

	if (c) {
	c->name = name;
	c->size = size;
	c->ctor = ctor;
	c->dtor = dtor;
	/* ignore alignment unless it's forced */
	c->align = (flags & SLAB_MUST_HWCACHE_ALIGN) ? SLOB_ALIGN : 0;
	if (c->align < align)
	c->align = align;
	}

	return c;
	}
	EXPORT_SYMBOL(kmem_cache_create);

	int kmem_cache_destroy(struct kmem_cache *c)
	{
	slob_free(c, sizeof(struct kmem_cache));
	return 0;
	}
	EXPORT_SYMBOL(kmem_cache_destroy);

	void kmem_cache_alloc(struct kmem_cache c, gfp_t flags)
	{
	void *b;

	if (c->size < PAGE_SIZE)
	b = slob_alloc(c->size, flags, c->align);
	else
	b = (void *)__get_free_pages(flags, find_order(c->size));

	if (c->ctor)
	c->ctor(b, c, SLAB_CTOR_CONSTRUCTOR);

	return b;
	}
	EXPORT_SYMBOL(kmem_cache_alloc);

	void kmem_cache_zalloc(struct kmem_cache c, gfp_t flags)
	{
	void *ret = kmem_cache_alloc(c, flags);
	if (ret)
	memset(ret, 0, c->size);

	return ret;
	}
	EXPORT_SYMBOL(kmem_cache_zalloc);

	void kmem_cache_free(struct kmem_cache c, void b)
	{
	if (c->dtor)
	c->dtor(b, c, 0);

	if (c->size < PAGE_SIZE)
	slob_free(b, c->size);
	else
	free_pages((unsigned long)b, find_order(c->size));
	}
	EXPORT_SYMBOL(kmem_cache_free);

	unsigned int kmem_cache_size(struct kmem_cache *c)
	{
	return c->size;
	}
	EXPORT_SYMBOL(kmem_cache_size);

	const char kmem_cache_name(struct kmem_cache c)
	{
	return c->name;
	}
	EXPORT_SYMBOL(kmem_cache_name);

	static struct timer_list slob_timer = TIMER_INITIALIZER(
	(void (*)(unsigned long))kmem_cache_init, 0, 0);

	void kmem_cache_init(void)
	{
	void *p = slob_alloc(PAGE_SIZE, 0, PAGE_SIZE-1);

	if (p)
	free_page((unsigned long)p);

	mod_timer(&slob_timer, jiffies + HZ);
	}

	atomic_t slab_reclaim_pages = ATOMIC_INIT(0);
	EXPORT_SYMBOL(slab_reclaim_pages);

	#ifdef CONFIG_SMP

	void *__alloc_percpu(size_t size)
	{
	int i;
	struct percpu_data pdata = kmalloc(sizeof (pdata), GFP_KERNEL);

	if (!pdata)
	return NULL;

	for_each_possible_cpu(i) {
	pdata->ptrs[i] = kmalloc(size, GFP_KERNEL);
	if (!pdata->ptrs[i])
	goto unwind_oom;
	memset(pdata->ptrs[i], 0, size);
	}

	/* Catch derefs w/o wrappers */
	return (void *) (~(unsigned long) pdata);

	unwind_oom:
	while (--i >= 0) {
	if (!cpu_possible(i))
	continue;
	kfree(pdata->ptrs[i]);
	}
	kfree(pdata);
	return NULL;
	}
	EXPORT_SYMBOL(__alloc_percpu);

	void
	free_percpu(const void *objp)
	{
	int i;
	struct percpu_data p = (struct percpu_data ) (~(unsigned long) objp);

	for_each_possible_cpu(i)
	kfree(p->ptrs[i]);

	kfree(p);
	}
	EXPORT_SYMBOL(free_percpu);

	#endif