Commit a35a3455 authored by Matthew Wilcox's avatar Matthew Wilcox
Browse files

Change dmapool free block management 



Use a list of free blocks within a page instead of using a bitmap.
Update documentation to reflect this.  As well as being a slight
reduction in memory allocation, locked ops and lines of code, it speeds
up a transaction processing benchmark by 0.4%.

Signed-off-by: default avatarMatthew Wilcox <willy@linux.intel.com>
parent 6182a094

mm/dmapool.c

+58 −61
Original line number Diff line number Diff line
@@ -17,7 +17,9 @@ 
 * The current design of this allocator is fairly simple.  The pool is

 * represented by the 'struct dma_pool' which keeps a doubly-linked list of

 * allocated pages.  Each page in the page_list is split into blocks of at

 * least 'size' bytes.

 * least 'size' bytes.  Free blocks are tracked in an unsorted singly-linked

 * list of free blocks within the page.  Used blocks aren't tracked, but we

 * keep a count of how many are currently allocated from each page.

 */



#include <linux/device.h>
@@ -38,7 +40,6 @@ 
struct dma_pool {		/* the pool */

	struct list_head page_list;

	spinlock_t lock;

	size_t blocks_per_page;

	size_t size;

	struct device *dev;

	size_t allocation;
@@ -51,8 +52,8 @@ struct dma_page { /* cacheable header for 'allocation' bytes */ 
	struct list_head page_list;

	void *vaddr;

	dma_addr_t dma;

	unsigned in_use;

	unsigned long bitmap[0];

	unsigned int in_use;

	unsigned int offset;

};



#define	POOL_TIMEOUT_JIFFIES	((100 /* msec */ * HZ) / 1000)
@@ -87,8 +88,8 @@ show_pools(struct device *dev, struct device_attribute *attr, char *buf) 


		/* per-pool info, no real statistics yet */

		temp = scnprintf(next, size, "%-16s %4u %4Zu %4Zu %2u\n",

				 pool->name,

				 blocks, pages * pool->blocks_per_page,

				 pool->name, blocks,

				 pages * (pool->allocation / pool->size),

				 pool->size, pages);

		size -= temp;

		next += temp;
@@ -132,8 +133,11 @@ struct dma_pool *dma_pool_create(const char *name, struct device *dev, 
		return NULL;

	}



	if (size == 0)

	if (size == 0) {

		return NULL;

	} else if (size < 4) {

		size = 4;

	}



	if ((size % align) != 0)

		size = ALIGN(size, align);
@@ -160,7 +164,6 @@ struct dma_pool *dma_pool_create(const char *name, struct device *dev, 
	spin_lock_init(&retval->lock);

	retval->size = size;

	retval->allocation = allocation;

	retval->blocks_per_page = allocation / size;

	init_waitqueue_head(&retval->waitq);



	if (dev) {
@@ -186,28 +189,36 @@ struct dma_pool *dma_pool_create(const char *name, struct device *dev, 
}

EXPORT_SYMBOL(dma_pool_create);



static void pool_initialise_page(struct dma_pool *pool, struct dma_page *page)

{

	unsigned int offset = 0;



	do {

		unsigned int next = offset + pool->size;

		if (unlikely((next + pool->size) >= pool->allocation))

			next = pool->allocation;

		*(int *)(page->vaddr + offset) = next;

		offset = next;

	} while (offset < pool->allocation);

}



static struct dma_page *pool_alloc_page(struct dma_pool *pool, gfp_t mem_flags)

{

	struct dma_page *page;

	int mapsize;



	mapsize = pool->blocks_per_page;

	mapsize = (mapsize + BITS_PER_LONG - 1) / BITS_PER_LONG;

	mapsize *= sizeof(long);



	page = kmalloc(mapsize + sizeof *page, mem_flags);

	page = kmalloc(sizeof(*page), mem_flags);

	if (!page)

		return NULL;

	page->vaddr = dma_alloc_coherent(pool->dev,

					 pool->allocation,

	page->vaddr = dma_alloc_coherent(pool->dev, pool->allocation,

					 &page->dma, mem_flags);

	if (page->vaddr) {

		memset(page->bitmap, 0xff, mapsize);	/* bit set == free */

#ifdef	CONFIG_DEBUG_SLAB

		memset(page->vaddr, POOL_POISON_FREED, pool->allocation);

#endif

		pool_initialise_page(pool, page);

		list_add(&page->page_list, &pool->page_list);

		page->in_use = 0;

		page->offset = 0;

	} else {

		kfree(page);

		page = NULL;
@@ -215,14 +226,9 @@ static struct dma_page *pool_alloc_page(struct dma_pool *pool, gfp_t mem_flags) 
	return page;

}



static inline int is_page_busy(int blocks, unsigned long *bitmap)

static inline int is_page_busy(struct dma_page *page)

{

	while (blocks > 0) {

		if (*bitmap++ != ~0UL)

			return 1;

		blocks -= BITS_PER_LONG;

	}

	return 0;

	return page->in_use != 0;

}



static void pool_free_page(struct dma_pool *pool, struct dma_page *page)
@@ -257,7 +263,7 @@ void dma_pool_destroy(struct dma_pool *pool) 
		struct dma_page *page;

		page = list_entry(pool->page_list.next,

				  struct dma_page, page_list);

		if (is_page_busy(pool->blocks_per_page, page->bitmap)) {

		if (is_page_busy(page)) {

			if (pool->dev)

				dev_err(pool->dev,

					"dma_pool_destroy %s, %p busy\n",
@@ -292,28 +298,15 @@ void *dma_pool_alloc(struct dma_pool *pool, gfp_t mem_flags, 
{

	unsigned long flags;

	struct dma_page *page;

	int map, block;

	size_t offset;

	void *retval;



	spin_lock_irqsave(&pool->lock, flags);

 restart:

	list_for_each_entry(page, &pool->page_list, page_list) {

		int i;

		/* only cachable accesses here ... */

		for (map = 0, i = 0;

		     i < pool->blocks_per_page; i += BITS_PER_LONG, map++) {

			if (page->bitmap[map] == 0)

				continue;

			block = ffz(~page->bitmap[map]);

			if ((i + block) < pool->blocks_per_page) {

				clear_bit(block, &page->bitmap[map]);

				offset = (BITS_PER_LONG * map) + block;

				offset *= pool->size;

		if (page->offset < pool->allocation)

			goto ready;

	}

		}

	}

	page = pool_alloc_page(pool, GFP_ATOMIC);

	if (!page) {

		if (mem_flags & __GFP_WAIT) {
@@ -333,10 +326,10 @@ void *dma_pool_alloc(struct dma_pool *pool, gfp_t mem_flags, 
		goto done;

	}



	clear_bit(0, &page->bitmap[0]);

	offset = 0;

 ready:

	page->in_use++;

	offset = page->offset;

	page->offset = *(int *)(page->vaddr + offset);

	retval = offset + page->vaddr;

	*handle = offset + page->dma;

#ifdef	CONFIG_DEBUG_SLAB
@@ -379,7 +372,7 @@ void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t dma) 
{

	struct dma_page *page;

	unsigned long flags;

	int map, block;

	unsigned int offset;



	page = pool_find_page(pool, dma);

	if (!page) {
@@ -393,13 +386,9 @@ void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t dma) 
		return;

	}



	block = dma - page->dma;

	block /= pool->size;

	map = block / BITS_PER_LONG;

	block %= BITS_PER_LONG;



	offset = vaddr - page->vaddr;

#ifdef	CONFIG_DEBUG_SLAB

	if (((dma - page->dma) + (void *)page->vaddr) != vaddr) {

	if ((dma - page->dma) != offset) {

		if (pool->dev)

			dev_err(pool->dev,

				"dma_pool_free %s, %p (bad vaddr)/%Lx\n",
@@ -410,28 +399,36 @@ void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t dma) 
			       pool->name, vaddr, (unsigned long long)dma);

		return;

	}

	if (page->bitmap[map] & (1UL << block)) {

	{

		unsigned int chain = page->offset;

		while (chain < pool->allocation) {

			if (chain != offset) {

				chain = *(int *)(page->vaddr + chain);

				continue;

			}

			if (pool->dev)

			dev_err(pool->dev,

				"dma_pool_free %s, dma %Lx already free\n",

				pool->name, (unsigned long long)dma);

				dev_err(pool->dev, "dma_pool_free %s, dma %Lx "

					"already free\n", pool->name,

					(unsigned long long)dma);

			else

			printk(KERN_ERR

			       "dma_pool_free %s, dma %Lx already free\n",

			       pool->name, (unsigned long long)dma);

				printk(KERN_ERR "dma_pool_free %s, dma %Lx "

					"already free\n", pool->name,

					(unsigned long long)dma);

			return;

		}

	}

	memset(vaddr, POOL_POISON_FREED, pool->size);

#endif



	spin_lock_irqsave(&pool->lock, flags);

	page->in_use--;

	set_bit(block, &page->bitmap[map]);

	*(int *)vaddr = page->offset;

	page->offset = offset;

	if (waitqueue_active(&pool->waitq))

		wake_up_locked(&pool->waitq);

	/*

	 * Resist a temptation to do

	 *    if (!is_page_busy(bpp, page->bitmap)) pool_free_page(pool, page);

	 *    if (!is_page_busy(page)) pool_free_page(pool, page);

	 * Better have a few empty pages hang around.

	 */

	spin_unlock_irqrestore(&pool->lock, flags);

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