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/*
14 * Reserve one vmemmap page, all vmemmap addresses are mapped to it. See
15 * Documentation/mm/vmemmap_dedup.rst.
16 */
17#define HUGETLB_VMEMMAP_RESERVE_SIZE PAGE_SIZE
18#define HUGETLB_VMEMMAP_RESERVE_PAGES (HUGETLB_VMEMMAP_RESERVE_SIZE / sizeof(struct page))
19
20#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
21int hugetlb_vmemmap_restore_folio(const struct hstate *h, struct folio *folio);
22long hugetlb_vmemmap_restore_folios(const struct hstate *h,
23 struct list_head *folio_list,
24 struct list_head *non_hvo_folios);
25void hugetlb_vmemmap_optimize_folio(const struct hstate *h, struct folio *folio);
26void hugetlb_vmemmap_optimize_folios(struct hstate *h, struct list_head *folio_list);
27
28static inline unsigned int hugetlb_vmemmap_size(const struct hstate *h)
29{
30 return pages_per_huge_page(h) * sizeof(struct page);
31}
32
33/*
34 * Return how many vmemmap size associated with a HugeTLB page that can be
35 * optimized and can be freed to the buddy allocator.
36 */
37static inline unsigned int hugetlb_vmemmap_optimizable_size(const struct hstate *h)
38{
39 int size = hugetlb_vmemmap_size(h) - HUGETLB_VMEMMAP_RESERVE_SIZE;
40
41 if (!is_power_of_2(n: sizeof(struct page)))
42 return 0;
43 return size > 0 ? size : 0;
44}
45#else
46static inline int hugetlb_vmemmap_restore_folio(const struct hstate *h, struct folio *folio)
47{
48 return 0;
49}
50
51static long hugetlb_vmemmap_restore_folios(const struct hstate *h,
52 struct list_head *folio_list,
53 struct list_head *non_hvo_folios)
54{
55 list_splice_init(folio_list, non_hvo_folios);
56 return 0;
57}
58
59static inline void hugetlb_vmemmap_optimize_folio(const struct hstate *h, struct folio *folio)
60{
61}
62
63static inline void hugetlb_vmemmap_optimize_folios(struct hstate *h, struct list_head *folio_list)
64{
65}
66
67static inline unsigned int hugetlb_vmemmap_optimizable_size(const struct hstate *h)
68{
69 return 0;
70}
71#endif /* CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP */
72
73static inline bool hugetlb_vmemmap_optimizable(const struct hstate *h)
74{
75 return hugetlb_vmemmap_optimizable_size(h) != 0;
76}
77#endif /* _LINUX_HUGETLB_VMEMMAP_H */
78

source code of linux/mm/hugetlb_vmemmap.h