Commit a0615780 authored by Vishal Moola (Oracle)'s avatar Vishal Moola (Oracle) Committed by Andrew Morton
Browse files

mm/vmalloc: request large order pages from buddy allocator 

Sometimes, vm_area_alloc_pages() will want many pages from the buddy
allocator.  Rather than making requests to the buddy allocator for at most
100 pages at a time, we can eagerly request large order pages a smaller
number of times.

We still split the large order pages down to order-0 as the rest of the
vmalloc code (and some callers) depend on it.  We still defer to the bulk
allocator and fallback path in case of order-0 pages or failure.

Running 1000 iterations of allocations on a small 4GB system finds:

1000 2mb allocations:
	[Baseline]			[This patch]
	real    46.310s			real    0m34.582
	user    0.001s			user    0.006s
	sys     46.058s			sys     0m34.365s

10000 200kb allocations:
	[Baseline]			[This patch]
	real    56.104s			real    0m43.696
	user    0.001s			user    0.003s
	sys     55.375s			sys     0m42.995s

Link: https://lkml.kernel.org/r/20251021194455.33351-2-vishal.moola@gmail.com


Signed-off-by: default avatarVishal Moola (Oracle) <vishal.moola@gmail.com>
Reviewed-by: default avatarUladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 645a3c42

mm/vmalloc.c

+36 −0
Original line number Diff line number Diff line
@@ -3619,8 +3619,44 @@ vm_area_alloc_pages(gfp_t gfp, int nid, 
		unsigned int order, unsigned int nr_pages, struct page **pages)

{

	unsigned int nr_allocated = 0;

	unsigned int nr_remaining = nr_pages;

	unsigned int max_attempt_order = MAX_PAGE_ORDER;

	struct page *page;

	int i;

	gfp_t large_gfp = (gfp &

		~(__GFP_DIRECT_RECLAIM | __GFP_NOFAIL | __GFP_COMP))

		| __GFP_NOWARN;

	unsigned int large_order = ilog2(nr_remaining);



	large_order = min(max_attempt_order, large_order);



	/*

	 * Initially, attempt to have the page allocator give us large order

	 * pages. Do not attempt allocating smaller than order chunks since

	 * __vmap_pages_range() expects physically contigous pages of exactly

	 * order long chunks.

	 */

	while (large_order > order && nr_remaining) {

		if (nid == NUMA_NO_NODE)

			page = alloc_pages_noprof(large_gfp, large_order);

		else

			page = alloc_pages_node_noprof(nid, large_gfp, large_order);



		if (unlikely(!page)) {

			max_attempt_order = --large_order;

			continue;

		}



		split_page(page, large_order);

		for (i = 0; i < (1U << large_order); i++)

			pages[nr_allocated + i] = page + i;



		nr_allocated += 1U << large_order;

		nr_remaining = nr_pages - nr_allocated;



		large_order = ilog2(nr_remaining);

		large_order = min(max_attempt_order, large_order);

	}



	/*

	 * For order-0 pages we make use of bulk allocator, if