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slob: remove bigblock tracking 

Remove the bigblock lists in favour of using compound pages and going directly
to the page allocator.  Allocation size is stored in page->private, which also
makes ksize more accurate than it previously was.

Saves ~.5K of code, and 12-24 bytes overhead per >= PAGE_SIZE allocation.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Nick Piggin 2007-07-15 23:38:08 -07:00 committed by Linus Torvalds
parent 95b35127f1
commit d87a133fc2
1 changed files with 29 additions and 74 deletions
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103
mm/slob.c
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@ -18,9 +18,11 @@
* Above this is an implementation of kmalloc/kfree. Blocks returned
* 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.
* __get_free_pages directly, allocating compound pages so the page order
* does not have to be separately tracked, and also stores the exact
* allocation size in page->private so that it can be used to accurately
* provide ksize(). These objects are detected in kfree() because slob_page()
* is false for them.
*
* SLAB is emulated on top of SLOB by simply calling constructors and
* destructors for every SLAB allocation. Objects are returned with the
@ -29,7 +31,8 @@
* 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.
* space overhead, and compound pages aren't needed for multi-page
* allocations.
*/
#include <linux/kernel.h>
@ -381,48 +384,26 @@ static void slob_free(void *block, int size)
* 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;
bigblock_t *bb;
unsigned long flags;
if (size < PAGE_SIZE - SLOB_UNIT) {
slob_t *m;
m = slob_alloc(size + SLOB_UNIT, gfp, 0);
if (m)
m->units = size;
return m+1;
} else {
void *ret;
ret = (void *) __get_free_pages(gfp | __GFP_COMP,
get_order(size));
if (ret) {
struct page *page;
page = virt_to_page(ret);
page->private = size;
}
return ret;
}
bb = slob_alloc(sizeof(bigblock_t), gfp, 0);
if (!bb)
return 0;
bb->order = get_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);
@ -462,59 +443,33 @@ 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;
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) {
*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);
WARN_ON(1);
return;
}
m = (slob_t *)block - 1;
slob_free(m, m->units + SLOB_UNIT);
return;
if (slob_page(sp)) {
slob_t *m = (slob_t *)block - 1;
slob_free(m, m->units + SLOB_UNIT);
} else
put_page(&sp->page);
}
EXPORT_SYMBOL(kfree);
/* can't use ksize for kmem_cache_alloc memory, only kmalloc */
size_t ksize(const void *block)
{
struct slob_page *sp;
bigblock_t *bb;
unsigned long flags;
if (!block)
return 0;
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) {
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;
if (slob_page(sp))
return ((slob_t *)block - 1)->units + SLOB_UNIT;
else
return sp->page.private;
}
struct kmem_cache {