leandrof/linux
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

mm: add alloc_pages_exact() and free_pages_exact()

Browse Source 
alloc_pages_exact() is similar to alloc_pages(), except that it allocates
the minimum number of pages to fulfill the request.  This is useful if you
want to allocate a very large buffer that is slightly larger than an even
power-of-two number of pages.  In that case, alloc_pages() will waste a
lot of memory.

I have a video driver that wants to allocate a 5MB buffer.  alloc_pages()
wiill waste 3MB of physically-contiguous memory.

Signed-off-by: Timur Tabi <timur@freescale.com>
Cc: Andi Kleen <andi@firstfloor.org>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Timur Tabi 2008-07-23 21:28:11 -07:00 committed by Linus Torvalds
parent 3560e249ab
commit 2be0ffe2b2
2 changed files with 56 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
include/linux/gfp.h
View File

@ -228,6 +228,9 @@ extern struct page *alloc_page_vma(gfp_t gfp_mask,
extern unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order);
extern unsigned long get_zeroed_page(gfp_t gfp_mask);
void *alloc_pages_exact(size_t size, gfp_t gfp_mask);
void free_pages_exact(void *virt, size_t size);
#define __get_free_page(gfp_mask) \
__get_free_pages((gfp_mask),0)

53
mm/page_alloc.c
View File

@ -1697,6 +1697,59 @@ void free_pages(unsigned long addr, unsigned int order)
EXPORT_SYMBOL(free_pages);
/**
* alloc_pages_exact - allocate an exact number physically-contiguous pages.
* @size: the number of bytes to allocate
* @gfp_mask: GFP flags for the allocation
*
* This function is similar to alloc_pages(), except that it allocates the
* minimum number of pages to satisfy the request. alloc_pages() can only
* allocate memory in power-of-two pages.
*
* This function is also limited by MAX_ORDER.
*
* Memory allocated by this function must be released by free_pages_exact().
*/
void *alloc_pages_exact(size_t size, gfp_t gfp_mask)
{
unsigned int order = get_order(size);
unsigned long addr;
addr = __get_free_pages(gfp_mask, order);
if (addr) {
unsigned long alloc_end = addr + (PAGE_SIZE << order);
unsigned long used = addr + PAGE_ALIGN(size);
split_page(virt_to_page(addr), order);
while (used < alloc_end) {
free_page(used);
used += PAGE_SIZE;
}
}
return (void *)addr;
}
EXPORT_SYMBOL(alloc_pages_exact);
/**
* free_pages_exact - release memory allocated via alloc_pages_exact()
* @virt: the value returned by alloc_pages_exact.
* @size: size of allocation, same value as passed to alloc_pages_exact().
*
* Release the memory allocated by a previous call to alloc_pages_exact.
*/
void free_pages_exact(void *virt, size_t size)
{
unsigned long addr = (unsigned long)virt;
unsigned long end = addr + PAGE_ALIGN(size);
while (addr < end) {
free_page(addr);
addr += PAGE_SIZE;
}
}
EXPORT_SYMBOL(free_pages_exact);
static unsigned int nr_free_zone_pages(int offset)
{
struct zoneref *z;