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33c3fc71 VD |
1 | #include <linux/init.h> |
2 | #include <linux/bootmem.h> | |
3 | #include <linux/fs.h> | |
4 | #include <linux/sysfs.h> | |
5 | #include <linux/kobject.h> | |
6 | #include <linux/mm.h> | |
7 | #include <linux/mmzone.h> | |
8 | #include <linux/pagemap.h> | |
9 | #include <linux/rmap.h> | |
10 | #include <linux/mmu_notifier.h> | |
11 | #include <linux/page_ext.h> | |
12 | #include <linux/page_idle.h> | |
13 | ||
14 | #define BITMAP_CHUNK_SIZE sizeof(u64) | |
15 | #define BITMAP_CHUNK_BITS (BITMAP_CHUNK_SIZE * BITS_PER_BYTE) | |
16 | ||
17 | /* | |
18 | * Idle page tracking only considers user memory pages, for other types of | |
19 | * pages the idle flag is always unset and an attempt to set it is silently | |
20 | * ignored. | |
21 | * | |
22 | * We treat a page as a user memory page if it is on an LRU list, because it is | |
23 | * always safe to pass such a page to rmap_walk(), which is essential for idle | |
24 | * page tracking. With such an indicator of user pages we can skip isolated | |
25 | * pages, but since there are not usually many of them, it will hardly affect | |
26 | * the overall result. | |
27 | * | |
28 | * This function tries to get a user memory page by pfn as described above. | |
29 | */ | |
30 | static struct page *page_idle_get_page(unsigned long pfn) | |
31 | { | |
32 | struct page *page; | |
33 | struct zone *zone; | |
34 | ||
35 | if (!pfn_valid(pfn)) | |
36 | return NULL; | |
37 | ||
38 | page = pfn_to_page(pfn); | |
39 | if (!page || !PageLRU(page) || | |
40 | !get_page_unless_zero(page)) | |
41 | return NULL; | |
42 | ||
43 | zone = page_zone(page); | |
44 | spin_lock_irq(&zone->lru_lock); | |
45 | if (unlikely(!PageLRU(page))) { | |
46 | put_page(page); | |
47 | page = NULL; | |
48 | } | |
49 | spin_unlock_irq(&zone->lru_lock); | |
50 | return page; | |
51 | } | |
52 | ||
53 | static int page_idle_clear_pte_refs_one(struct page *page, | |
54 | struct vm_area_struct *vma, | |
55 | unsigned long addr, void *arg) | |
56 | { | |
57 | struct mm_struct *mm = vma->vm_mm; | |
58 | spinlock_t *ptl; | |
59 | pmd_t *pmd; | |
60 | pte_t *pte; | |
61 | bool referenced = false; | |
62 | ||
63 | if (unlikely(PageTransHuge(page))) { | |
4b471e88 | 64 | pmd = page_check_address_pmd(page, mm, addr, &ptl); |
33c3fc71 VD |
65 | if (pmd) { |
66 | referenced = pmdp_clear_young_notify(vma, addr, pmd); | |
67 | spin_unlock(ptl); | |
68 | } | |
69 | } else { | |
70 | pte = page_check_address(page, mm, addr, &ptl, 0); | |
71 | if (pte) { | |
72 | referenced = ptep_clear_young_notify(vma, addr, pte); | |
73 | pte_unmap_unlock(pte, ptl); | |
74 | } | |
75 | } | |
76 | if (referenced) { | |
77 | clear_page_idle(page); | |
78 | /* | |
79 | * We cleared the referenced bit in a mapping to this page. To | |
80 | * avoid interference with page reclaim, mark it young so that | |
81 | * page_referenced() will return > 0. | |
82 | */ | |
83 | set_page_young(page); | |
84 | } | |
85 | return SWAP_AGAIN; | |
86 | } | |
87 | ||
88 | static void page_idle_clear_pte_refs(struct page *page) | |
89 | { | |
90 | /* | |
91 | * Since rwc.arg is unused, rwc is effectively immutable, so we | |
92 | * can make it static const to save some cycles and stack. | |
93 | */ | |
94 | static const struct rmap_walk_control rwc = { | |
95 | .rmap_one = page_idle_clear_pte_refs_one, | |
96 | .anon_lock = page_lock_anon_vma_read, | |
97 | }; | |
98 | bool need_lock; | |
99 | ||
100 | if (!page_mapped(page) || | |
101 | !page_rmapping(page)) | |
102 | return; | |
103 | ||
104 | need_lock = !PageAnon(page) || PageKsm(page); | |
105 | if (need_lock && !trylock_page(page)) | |
106 | return; | |
107 | ||
108 | rmap_walk(page, (struct rmap_walk_control *)&rwc); | |
109 | ||
110 | if (need_lock) | |
111 | unlock_page(page); | |
112 | } | |
113 | ||
114 | static ssize_t page_idle_bitmap_read(struct file *file, struct kobject *kobj, | |
115 | struct bin_attribute *attr, char *buf, | |
116 | loff_t pos, size_t count) | |
117 | { | |
118 | u64 *out = (u64 *)buf; | |
119 | struct page *page; | |
120 | unsigned long pfn, end_pfn; | |
121 | int bit; | |
122 | ||
123 | if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE) | |
124 | return -EINVAL; | |
125 | ||
126 | pfn = pos * BITS_PER_BYTE; | |
127 | if (pfn >= max_pfn) | |
128 | return 0; | |
129 | ||
130 | end_pfn = pfn + count * BITS_PER_BYTE; | |
131 | if (end_pfn > max_pfn) | |
132 | end_pfn = ALIGN(max_pfn, BITMAP_CHUNK_BITS); | |
133 | ||
134 | for (; pfn < end_pfn; pfn++) { | |
135 | bit = pfn % BITMAP_CHUNK_BITS; | |
136 | if (!bit) | |
137 | *out = 0ULL; | |
138 | page = page_idle_get_page(pfn); | |
139 | if (page) { | |
140 | if (page_is_idle(page)) { | |
141 | /* | |
142 | * The page might have been referenced via a | |
143 | * pte, in which case it is not idle. Clear | |
144 | * refs and recheck. | |
145 | */ | |
146 | page_idle_clear_pte_refs(page); | |
147 | if (page_is_idle(page)) | |
148 | *out |= 1ULL << bit; | |
149 | } | |
150 | put_page(page); | |
151 | } | |
152 | if (bit == BITMAP_CHUNK_BITS - 1) | |
153 | out++; | |
154 | cond_resched(); | |
155 | } | |
156 | return (char *)out - buf; | |
157 | } | |
158 | ||
159 | static ssize_t page_idle_bitmap_write(struct file *file, struct kobject *kobj, | |
160 | struct bin_attribute *attr, char *buf, | |
161 | loff_t pos, size_t count) | |
162 | { | |
163 | const u64 *in = (u64 *)buf; | |
164 | struct page *page; | |
165 | unsigned long pfn, end_pfn; | |
166 | int bit; | |
167 | ||
168 | if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE) | |
169 | return -EINVAL; | |
170 | ||
171 | pfn = pos * BITS_PER_BYTE; | |
172 | if (pfn >= max_pfn) | |
173 | return -ENXIO; | |
174 | ||
175 | end_pfn = pfn + count * BITS_PER_BYTE; | |
176 | if (end_pfn > max_pfn) | |
177 | end_pfn = ALIGN(max_pfn, BITMAP_CHUNK_BITS); | |
178 | ||
179 | for (; pfn < end_pfn; pfn++) { | |
180 | bit = pfn % BITMAP_CHUNK_BITS; | |
181 | if ((*in >> bit) & 1) { | |
182 | page = page_idle_get_page(pfn); | |
183 | if (page) { | |
184 | page_idle_clear_pte_refs(page); | |
185 | set_page_idle(page); | |
186 | put_page(page); | |
187 | } | |
188 | } | |
189 | if (bit == BITMAP_CHUNK_BITS - 1) | |
190 | in++; | |
191 | cond_resched(); | |
192 | } | |
193 | return (char *)in - buf; | |
194 | } | |
195 | ||
196 | static struct bin_attribute page_idle_bitmap_attr = | |
197 | __BIN_ATTR(bitmap, S_IRUSR | S_IWUSR, | |
198 | page_idle_bitmap_read, page_idle_bitmap_write, 0); | |
199 | ||
200 | static struct bin_attribute *page_idle_bin_attrs[] = { | |
201 | &page_idle_bitmap_attr, | |
202 | NULL, | |
203 | }; | |
204 | ||
205 | static struct attribute_group page_idle_attr_group = { | |
206 | .bin_attrs = page_idle_bin_attrs, | |
207 | .name = "page_idle", | |
208 | }; | |
209 | ||
210 | #ifndef CONFIG_64BIT | |
211 | static bool need_page_idle(void) | |
212 | { | |
213 | return true; | |
214 | } | |
215 | struct page_ext_operations page_idle_ops = { | |
216 | .need = need_page_idle, | |
217 | }; | |
218 | #endif | |
219 | ||
220 | static int __init page_idle_init(void) | |
221 | { | |
222 | int err; | |
223 | ||
224 | err = sysfs_create_group(mm_kobj, &page_idle_attr_group); | |
225 | if (err) { | |
226 | pr_err("page_idle: register sysfs failed\n"); | |
227 | return err; | |
228 | } | |
229 | return 0; | |
230 | } | |
231 | subsys_initcall(page_idle_init); |