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Change dmapool free block management

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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: Matthew Wilcox <willy@linux.intel.com>
This commit is contained in:
Matthew Wilcox 2007-12-03 14:08:28 -05:00
parent 6182a0943a
commit a35a345514
1 changed files with 58 additions and 61 deletions
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119
mm/dmapool.c
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@ -17,7 +17,9 @@
* The current design of this allocator is fairly simple. The pool is * 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 * 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 * 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> #include <linux/device.h>
@ -38,7 +40,6 @@
struct dma_pool { /* the pool */ struct dma_pool { /* the pool */
struct list_head page_list; struct list_head page_list;
spinlock_t lock; spinlock_t lock;
size_t blocks_per_page;
size_t size; size_t size;
struct device *dev; struct device *dev;
size_t allocation; size_t allocation;
@ -51,8 +52,8 @@ struct dma_page { /* cacheable header for 'allocation' bytes */
struct list_head page_list; struct list_head page_list;
void *vaddr; void *vaddr;
dma_addr_t dma; dma_addr_t dma;
unsigned in_use; unsigned int in_use;
unsigned long bitmap[0]; unsigned int offset;
}; };
#define POOL_TIMEOUT_JIFFIES ((100 /* msec */ * HZ) / 1000) #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 */ /* per-pool info, no real statistics yet */
temp = scnprintf(next, size, "%-16s %4u %4Zu %4Zu %2u\n", temp = scnprintf(next, size, "%-16s %4u %4Zu %4Zu %2u\n",
pool->name, pool->name, blocks,
blocks, pages * pool->blocks_per_page, pages * (pool->allocation / pool->size),
pool->size, pages); pool->size, pages);
size -= temp; size -= temp;
next += temp; next += temp;
@ -132,8 +133,11 @@ struct dma_pool *dma_pool_create(const char *name, struct device *dev,
return NULL; return NULL;
} }
if (size == 0) if (size == 0) {
return NULL; return NULL;
} else if (size < 4) {
size = 4;
}
if ((size % align) != 0) if ((size % align) != 0)
size = ALIGN(size, align); 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); spin_lock_init(&retval->lock);
retval->size = size; retval->size = size;
retval->allocation = allocation; retval->allocation = allocation;
retval->blocks_per_page = allocation / size;
init_waitqueue_head(&retval->waitq); init_waitqueue_head(&retval->waitq);
if (dev) { if (dev) {
@ -186,28 +189,36 @@ struct dma_pool *dma_pool_create(const char *name, struct device *dev,
} }
EXPORT_SYMBOL(dma_pool_create); 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) static struct dma_page *pool_alloc_page(struct dma_pool *pool, gfp_t mem_flags)
{ {
struct dma_page *page; struct dma_page *page;
int mapsize;
mapsize = pool->blocks_per_page; page = kmalloc(sizeof(*page), mem_flags);
mapsize = (mapsize + BITS_PER_LONG - 1) / BITS_PER_LONG;
mapsize *= sizeof(long);
page = kmalloc(mapsize + sizeof *page, mem_flags);
if (!page) if (!page)
return NULL; return NULL;
page->vaddr = dma_alloc_coherent(pool->dev, page->vaddr = dma_alloc_coherent(pool->dev, pool->allocation,
pool->allocation,
&page->dma, mem_flags); &page->dma, mem_flags);
if (page->vaddr) { if (page->vaddr) {
memset(page->bitmap, 0xff, mapsize); /* bit set == free */
#ifdef CONFIG_DEBUG_SLAB #ifdef CONFIG_DEBUG_SLAB
memset(page->vaddr, POOL_POISON_FREED, pool->allocation); memset(page->vaddr, POOL_POISON_FREED, pool->allocation);
#endif #endif
pool_initialise_page(pool, page);
list_add(&page->page_list, &pool->page_list); list_add(&page->page_list, &pool->page_list);
page->in_use = 0; page->in_use = 0;
page->offset = 0;
} else { } else {
kfree(page); kfree(page);
page = NULL; page = NULL;
@ -215,14 +226,9 @@ static struct dma_page *pool_alloc_page(struct dma_pool *pool, gfp_t mem_flags)
return page; 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) { return page->in_use != 0;
if (*bitmap++ != ~0UL)
return 1;
blocks -= BITS_PER_LONG;
}
return 0;
} }
static void pool_free_page(struct dma_pool *pool, struct dma_page *page) 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; struct dma_page *page;
page = list_entry(pool->page_list.next, page = list_entry(pool->page_list.next,
struct dma_page, page_list); struct dma_page, page_list);
if (is_page_busy(pool->blocks_per_page, page->bitmap)) { if (is_page_busy(page)) {
if (pool->dev) if (pool->dev)
dev_err(pool->dev, dev_err(pool->dev,
"dma_pool_destroy %s, %p busy\n", "dma_pool_destroy %s, %p busy\n",
@ -292,27 +298,14 @@ void *dma_pool_alloc(struct dma_pool *pool, gfp_t mem_flags,
{ {
unsigned long flags; unsigned long flags;
struct dma_page *page; struct dma_page *page;
int map, block;
size_t offset; size_t offset;
void *retval; void *retval;
spin_lock_irqsave(&pool->lock, flags); spin_lock_irqsave(&pool->lock, flags);
restart: restart:
list_for_each_entry(page, &pool->page_list, page_list) { list_for_each_entry(page, &pool->page_list, page_list) {
int i; if (page->offset < pool->allocation)
/* only cachable accesses here ... */ goto ready;
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;
goto ready;
}
}
} }
page = pool_alloc_page(pool, GFP_ATOMIC); page = pool_alloc_page(pool, GFP_ATOMIC);
if (!page) { if (!page) {
@ -333,10 +326,10 @@ void *dma_pool_alloc(struct dma_pool *pool, gfp_t mem_flags,
goto done; goto done;
} }
clear_bit(0, &page->bitmap[0]);
offset = 0;
ready: ready:
page->in_use++; page->in_use++;
offset = page->offset;
page->offset = *(int *)(page->vaddr + offset);
retval = offset + page->vaddr; retval = offset + page->vaddr;
*handle = offset + page->dma; *handle = offset + page->dma;
#ifdef CONFIG_DEBUG_SLAB #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; struct dma_page *page;
unsigned long flags; unsigned long flags;
int map, block; unsigned int offset;
page = pool_find_page(pool, dma); page = pool_find_page(pool, dma);
if (!page) { if (!page) {
@ -393,13 +386,9 @@ void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t dma)
return; return;
} }
block = dma - page->dma; offset = vaddr - page->vaddr;
block /= pool->size;
map = block / BITS_PER_LONG;
block %= BITS_PER_LONG;
#ifdef CONFIG_DEBUG_SLAB #ifdef CONFIG_DEBUG_SLAB
if (((dma - page->dma) + (void *)page->vaddr) != vaddr) { if ((dma - page->dma) != offset) {
if (pool->dev) if (pool->dev)
dev_err(pool->dev, dev_err(pool->dev,
"dma_pool_free %s, %p (bad vaddr)/%Lx\n", "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); pool->name, vaddr, (unsigned long long)dma);
return; return;
} }
if (page->bitmap[map] & (1UL << block)) { {
if (pool->dev) unsigned int chain = page->offset;
dev_err(pool->dev, while (chain < pool->allocation) {
"dma_pool_free %s, dma %Lx already free\n", if (chain != offset) {
pool->name, (unsigned long long)dma); chain = *(int *)(page->vaddr + chain);
else continue;
printk(KERN_ERR }
"dma_pool_free %s, dma %Lx already free\n", if (pool->dev)
pool->name, (unsigned long long)dma); dev_err(pool->dev, "dma_pool_free %s, dma %Lx "
return; "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);
return;
}
} }
memset(vaddr, POOL_POISON_FREED, pool->size); memset(vaddr, POOL_POISON_FREED, pool->size);
#endif #endif
spin_lock_irqsave(&pool->lock, flags); spin_lock_irqsave(&pool->lock, flags);
page->in_use--; page->in_use--;
set_bit(block, &page->bitmap[map]); *(int *)vaddr = page->offset;
page->offset = offset;
if (waitqueue_active(&pool->waitq)) if (waitqueue_active(&pool->waitq))
wake_up_locked(&pool->waitq); wake_up_locked(&pool->waitq);
/* /*
* Resist a temptation to do * 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. * Better have a few empty pages hang around.
*/ */
spin_unlock_irqrestore(&pool->lock, flags); spin_unlock_irqrestore(&pool->lock, flags);