linux - include/linux/ksm.h

164 lines · 4.4 KiB

1	/* SPDX-License-Identifier: GPL-2.0 */
2	#ifndef __LINUX_KSM_H
3	#define __LINUX_KSM_H
4	/*
5	* Memory merging support.
6	*
7	* This code enables dynamic sharing of identical pages found in different
8	* memory areas, even if they are not shared by fork().
9	*/
10
11	#include <linux/bitops.h>
12	#include <linux/mm.h>
13	#include <linux/pagemap.h>
14	#include <linux/rmap.h>
15	#include <linux/sched.h>
16
17	#ifdef CONFIG_KSM
18	int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
19	unsigned long end, int advice, vm_flags_t *vm_flags);
20	vma_flags_t ksm_vma_flags(struct mm_struct mm, const struct file file,
21	vma_flags_t vma_flags);
22	int ksm_enable_merge_any(struct mm_struct *mm);
23	int ksm_disable_merge_any(struct mm_struct *mm);
24	int ksm_disable(struct mm_struct *mm);
25
26	int __ksm_enter(struct mm_struct *mm);
27	void __ksm_exit(struct mm_struct *mm);
28	/*
29	* To identify zeropages that were mapped by KSM, we reuse the dirty bit
30	* in the PTE. If the PTE is dirty, the zeropage was mapped by KSM when
31	* deduplicating memory.
32	*/
33	#define is_ksm_zero_pte(pte) (is_zero_pfn(pte_pfn(pte)) && pte_dirty(pte))
34
35	extern atomic_long_t ksm_zero_pages;
36
37	static inline void ksm_map_zero_page(struct mm_struct *mm)
38	{
39	atomic_long_inc(&ksm_zero_pages);
40	atomic_long_inc(&mm->ksm_zero_pages);
41	}
42
43	static inline void ksm_might_unmap_zero_page(struct mm_struct *mm, pte_t pte)
44	{
45	if (is_ksm_zero_pte(pte)) {
46	atomic_long_dec(&ksm_zero_pages);
47	atomic_long_dec(&mm->ksm_zero_pages);
48	}
49	}
50
51	static inline long mm_ksm_zero_pages(struct mm_struct *mm)
52	{
53	return atomic_long_read(&mm->ksm_zero_pages);
54	}
55
56	static inline void ksm_fork(struct mm_struct mm, struct mm_struct oldmm)
57	{
58	/* Adding mm to ksm is best effort on fork. */
59	if (mm_flags_test(MMF_VM_MERGEABLE, oldmm)) {
60	long nr_ksm_zero_pages = atomic_long_read(&mm->ksm_zero_pages);
61
62	mm->ksm_merging_pages = 0;
63	mm->ksm_rmap_items = 0;
64	atomic_long_add(nr_ksm_zero_pages, &ksm_zero_pages);
65	__ksm_enter(mm);
66	}
67	}
68
69	static inline int ksm_execve(struct mm_struct *mm)
70	{
71	if (mm_flags_test(MMF_VM_MERGE_ANY, mm))
72	return __ksm_enter(mm);
73
74	return 0;
75	}
76
77	static inline void ksm_exit(struct mm_struct *mm)
78	{
79	if (mm_flags_test(MMF_VM_MERGEABLE, mm))
80	__ksm_exit(mm);
81	}
82
83	/*
84	* When do_swap_page() first faults in from swap what used to be a KSM page,
85	* no problem, it will be assigned to this vma's anon_vma; but thereafter,
86	* it might be faulted into a different anon_vma (or perhaps to a different
87	* offset in the same anon_vma). do_swap_page() cannot do all the locking
88	* needed to reconstitute a cross-anon_vma KSM page: for now it has to make
89	* a copy, and leave remerging the pages to a later pass of ksmd.
90	*
91	* We'd like to make this conditional on vma->vm_flags & VM_MERGEABLE,
92	* but what if the vma was unmerged while the page was swapped out?
93	*/
94	struct folio ksm_might_need_to_copy(struct folio folio,
95	struct vm_area_struct *vma, unsigned long addr);
96
97	void rmap_walk_ksm(struct folio folio, struct rmap_walk_control rwc);
98	void folio_migrate_ksm(struct folio newfolio, struct folio folio);
99	void collect_procs_ksm(const struct folio folio, const struct page page,
100	struct list_head *to_kill, int force_early);
101	long ksm_process_profit(struct mm_struct *);
102	bool ksm_process_mergeable(struct mm_struct *mm);
103
104	#else /* !CONFIG_KSM */
105
106	static inline vma_flags_t ksm_vma_flags(struct mm_struct *mm,
107	const struct file *file, vma_flags_t vma_flags)
108	{
109	return vma_flags;
110	}
111
112	static inline int ksm_disable(struct mm_struct *mm)
113	{
114	return 0;
115	}
116
117	static inline void ksm_fork(struct mm_struct mm, struct mm_struct oldmm)
118	{
119	}
120
121	static inline int ksm_execve(struct mm_struct *mm)
122	{
123	return 0;
124	}
125
126	static inline void ksm_exit(struct mm_struct *mm)
127	{
128	}
129
130	static inline void ksm_might_unmap_zero_page(struct mm_struct *mm, pte_t pte)
131	{
132	}
133
134	static inline void collect_procs_ksm(const struct folio *folio,
135	const struct page page, struct list_head to_kill,
136	int force_early)
137	{
138	}
139
140	#ifdef CONFIG_MMU
141	static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
142	unsigned long end, int advice, vm_flags_t *vm_flags)
143	{
144	return 0;
145	}
146
147	static inline struct folio ksm_might_need_to_copy(struct folio folio,
148	struct vm_area_struct *vma, unsigned long addr)
149	{
150	return folio;
151	}
152
153	static inline void rmap_walk_ksm(struct folio *folio,
154	struct rmap_walk_control *rwc)
155	{
156	}
157
158	static inline void folio_migrate_ksm(struct folio newfolio, struct folio old)
159	{
160	}
161	#endif /* CONFIG_MMU */
162	#endif /* !CONFIG_KSM */
163
164	#endif /* __LINUX_KSM_H */