Commit df48a5f7 authored by Liam R. Howlett's avatar Liam R. Howlett Committed by Andrew Morton
Browse files

mm/page_alloc: reduce potential fragmentation in make_alloc_exact() 

Try to avoid using the left over split page on the next request for a page
by calling __free_pages_ok() with FPI_TO_TAIL.  This increases the
potential of defragmenting memory when it's used for a short period of
time.

Link: https://lkml.kernel.org/r/20220531185626.yvlmymbxyoe5vags@revolver


Signed-off-by: default avatarLiam R. Howlett <Liam.Howlett@oracle.com>
Suggested-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 08ac8552

mm/page_alloc.c

+12 −8
Original line number Diff line number Diff line
@@ -5784,14 +5784,18 @@ static void *make_alloc_exact(unsigned long addr, unsigned int order, 
		size_t size)

{

	if (addr) {

		unsigned long alloc_end = addr + (PAGE_SIZE << order);

		unsigned long used = addr + PAGE_ALIGN(size);

		unsigned long nr = DIV_ROUND_UP(size, PAGE_SIZE);

		struct page *page = virt_to_page((void *)addr);

		struct page *last = page + nr;



		split_page(virt_to_page((void *)addr), order);

		while (used < alloc_end) {

			free_page(used);

			used += PAGE_SIZE;

		}

		split_page_owner(page, 1 << order);

		split_page_memcg(page, 1 << order);

		while (page < --last)

			set_page_refcounted(last);



		last = page + (1UL << order);

		for (page += nr; page < last; page++)

			__free_pages_ok(page, 0, FPI_TO_TAIL);

	}

	return (void *)addr;

}