1// SPDX-License-Identifier: GPL-2.0
 2/*
 3 * HugeTLB Vmemmap Optimization (HVO)
 4 *
 5 * Copyright (c) 2020, ByteDance. All rights reserved.
 6 *
 7 *     Author: Muchun Song <songmuchun@bytedance.com>
 8 */
 9#ifndef _LINUX_HUGETLB_VMEMMAP_H
10#define _LINUX_HUGETLB_VMEMMAP_H
11#include <linux/hugetlb.h>
12
13#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
14int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head);
15void hugetlb_vmemmap_optimize(const struct hstate *h, struct page *head);
16
17/*
18 * Reserve one vmemmap page, all vmemmap addresses are mapped to it. See
19 * Documentation/vm/vmemmap_dedup.rst.
20 */
21#define HUGETLB_VMEMMAP_RESERVE_SIZE	PAGE_SIZE
22
23static inline unsigned int hugetlb_vmemmap_size(const struct hstate *h)
24{
25	return pages_per_huge_page(h) * sizeof(struct page);
26}
27
28/*
29 * Return how many vmemmap size associated with a HugeTLB page that can be
30 * optimized and can be freed to the buddy allocator.
31 */
32static inline unsigned int hugetlb_vmemmap_optimizable_size(const struct hstate *h)
33{
34	int size = hugetlb_vmemmap_size(h) - HUGETLB_VMEMMAP_RESERVE_SIZE;
35
36	if (!is_power_of_2(sizeof(struct page)))
37		return 0;
38	return size > 0 ? size : 0;
39}
40#else
41static inline int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head)
42{
43	return 0;
44}
45
46static inline void hugetlb_vmemmap_optimize(const struct hstate *h, struct page *head)
47{
48}
49
50static inline unsigned int hugetlb_vmemmap_optimizable_size(const struct hstate *h)
51{
52	return 0;
53}
54#endif /* CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP */
55
56static inline bool hugetlb_vmemmap_optimizable(const struct hstate *h)
57{
58	return hugetlb_vmemmap_optimizable_size(h) != 0;
59}
60#endif /* _LINUX_HUGETLB_VMEMMAP_H */