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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 */
30static 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
53static 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 pmd_t *pmd;
59 pte_t *pte;
60 spinlock_t *ptl;
61 bool referenced = false;
62
63 if (!page_check_address_transhuge(page, mm, addr, &pmd, &pte, &ptl))
64 return SWAP_AGAIN;
65
66 if (pte) {
67 referenced = ptep_clear_young_notify(vma, addr, pte);
68 pte_unmap(pte);
69 } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
70 referenced = pmdp_clear_young_notify(vma, addr, pmd);
71 } else {
72 /* unexpected pmd-mapped page? */
73 WARN_ON_ONCE(1);
74 }
75
76 spin_unlock(ptl);
77
78 if (referenced) {
79 clear_page_idle(page);
80 /*
81 * We cleared the referenced bit in a mapping to this page. To
82 * avoid interference with page reclaim, mark it young so that
83 * page_referenced() will return > 0.
84 */
85 set_page_young(page);
86 }
87 return SWAP_AGAIN;
88}
89
90static void page_idle_clear_pte_refs(struct page *page)
91{
92 /*
93 * Since rwc.arg is unused, rwc is effectively immutable, so we
94 * can make it static const to save some cycles and stack.
95 */
96 static const struct rmap_walk_control rwc = {
97 .rmap_one = page_idle_clear_pte_refs_one,
98 .anon_lock = page_lock_anon_vma_read,
99 };
100 bool need_lock;
101
102 if (!page_mapped(page) ||
103 !page_rmapping(page))
104 return;
105
106 need_lock = !PageAnon(page) || PageKsm(page);
107 if (need_lock && !trylock_page(page))
108 return;
109
110 rmap_walk(page, (struct rmap_walk_control *)&rwc);
111
112 if (need_lock)
113 unlock_page(page);
114}
115
116static ssize_t page_idle_bitmap_read(struct file *file, struct kobject *kobj,
117 struct bin_attribute *attr, char *buf,
118 loff_t pos, size_t count)
119{
120 u64 *out = (u64 *)buf;
121 struct page *page;
122 unsigned long pfn, end_pfn;
123 int bit;
124
125 if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE)
126 return -EINVAL;
127
128 pfn = pos * BITS_PER_BYTE;
129 if (pfn >= max_pfn)
130 return 0;
131
132 end_pfn = pfn + count * BITS_PER_BYTE;
133 if (end_pfn > max_pfn)
134 end_pfn = ALIGN(max_pfn, BITMAP_CHUNK_BITS);
135
136 for (; pfn < end_pfn; pfn++) {
137 bit = pfn % BITMAP_CHUNK_BITS;
138 if (!bit)
139 *out = 0ULL;
140 page = page_idle_get_page(pfn);
141 if (page) {
142 if (page_is_idle(page)) {
143 /*
144 * The page might have been referenced via a
145 * pte, in which case it is not idle. Clear
146 * refs and recheck.
147 */
148 page_idle_clear_pte_refs(page);
149 if (page_is_idle(page))
150 *out |= 1ULL << bit;
151 }
152 put_page(page);
153 }
154 if (bit == BITMAP_CHUNK_BITS - 1)
155 out++;
156 cond_resched();
157 }
158 return (char *)out - buf;
159}
160
161static ssize_t page_idle_bitmap_write(struct file *file, struct kobject *kobj,
162 struct bin_attribute *attr, char *buf,
163 loff_t pos, size_t count)
164{
165 const u64 *in = (u64 *)buf;
166 struct page *page;
167 unsigned long pfn, end_pfn;
168 int bit;
169
170 if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE)
171 return -EINVAL;
172
173 pfn = pos * BITS_PER_BYTE;
174 if (pfn >= max_pfn)
175 return -ENXIO;
176
177 end_pfn = pfn + count * BITS_PER_BYTE;
178 if (end_pfn > max_pfn)
179 end_pfn = ALIGN(max_pfn, BITMAP_CHUNK_BITS);
180
181 for (; pfn < end_pfn; pfn++) {
182 bit = pfn % BITMAP_CHUNK_BITS;
183 if ((*in >> bit) & 1) {
184 page = page_idle_get_page(pfn);
185 if (page) {
186 page_idle_clear_pte_refs(page);
187 set_page_idle(page);
188 put_page(page);
189 }
190 }
191 if (bit == BITMAP_CHUNK_BITS - 1)
192 in++;
193 cond_resched();
194 }
195 return (char *)in - buf;
196}
197
198static struct bin_attribute page_idle_bitmap_attr =
199 __BIN_ATTR(bitmap, S_IRUSR | S_IWUSR,
200 page_idle_bitmap_read, page_idle_bitmap_write, 0);
201
202static struct bin_attribute *page_idle_bin_attrs[] = {
203 &page_idle_bitmap_attr,
204 NULL,
205};
206
207static struct attribute_group page_idle_attr_group = {
208 .bin_attrs = page_idle_bin_attrs,
209 .name = "page_idle",
210};
211
212#ifndef CONFIG_64BIT
213static bool need_page_idle(void)
214{
215 return true;
216}
217struct page_ext_operations page_idle_ops = {
218 .need = need_page_idle,
219};
220#endif
221
222static int __init page_idle_init(void)
223{
224 int err;
225
226 err = sysfs_create_group(mm_kobj, &page_idle_attr_group);
227 if (err) {
228 pr_err("page_idle: register sysfs failed\n");
229 return err;
230 }
231 return 0;
232}
233subsys_initcall(page_idle_init);
1// SPDX-License-Identifier: GPL-2.0
2#include <linux/init.h>
3#include <linux/memblock.h>
4#include <linux/fs.h>
5#include <linux/sysfs.h>
6#include <linux/kobject.h>
7#include <linux/memory_hotplug.h>
8#include <linux/mm.h>
9#include <linux/mmzone.h>
10#include <linux/pagemap.h>
11#include <linux/rmap.h>
12#include <linux/mmu_notifier.h>
13#include <linux/page_ext.h>
14#include <linux/page_idle.h>
15
16#include "internal.h"
17
18#define BITMAP_CHUNK_SIZE sizeof(u64)
19#define BITMAP_CHUNK_BITS (BITMAP_CHUNK_SIZE * BITS_PER_BYTE)
20
21/*
22 * Idle page tracking only considers user memory pages, for other types of
23 * pages the idle flag is always unset and an attempt to set it is silently
24 * ignored.
25 *
26 * We treat a page as a user memory page if it is on an LRU list, because it is
27 * always safe to pass such a page to rmap_walk(), which is essential for idle
28 * page tracking. With such an indicator of user pages we can skip isolated
29 * pages, but since there are not usually many of them, it will hardly affect
30 * the overall result.
31 *
32 * This function tries to get a user memory page by pfn as described above.
33 */
34static struct page *page_idle_get_page(unsigned long pfn)
35{
36 struct page *page = pfn_to_online_page(pfn);
37
38 if (!page || !PageLRU(page) ||
39 !get_page_unless_zero(page))
40 return NULL;
41
42 if (unlikely(!PageLRU(page))) {
43 put_page(page);
44 page = NULL;
45 }
46 return page;
47}
48
49static bool page_idle_clear_pte_refs_one(struct folio *folio,
50 struct vm_area_struct *vma,
51 unsigned long addr, void *arg)
52{
53 DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, addr, 0);
54 bool referenced = false;
55
56 while (page_vma_mapped_walk(&pvmw)) {
57 addr = pvmw.address;
58 if (pvmw.pte) {
59 /*
60 * For PTE-mapped THP, one sub page is referenced,
61 * the whole THP is referenced.
62 */
63 if (ptep_clear_young_notify(vma, addr, pvmw.pte))
64 referenced = true;
65 } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
66 if (pmdp_clear_young_notify(vma, addr, pvmw.pmd))
67 referenced = true;
68 } else {
69 /* unexpected pmd-mapped page? */
70 WARN_ON_ONCE(1);
71 }
72 }
73
74 if (referenced) {
75 folio_clear_idle(folio);
76 /*
77 * We cleared the referenced bit in a mapping to this page. To
78 * avoid interference with page reclaim, mark it young so that
79 * folio_referenced() will return > 0.
80 */
81 folio_set_young(folio);
82 }
83 return true;
84}
85
86static void page_idle_clear_pte_refs(struct page *page)
87{
88 struct folio *folio = page_folio(page);
89
90 /*
91 * Since rwc.try_lock is unused, rwc is effectively immutable, so we
92 * can make it static to save some cycles and stack.
93 */
94 static struct rmap_walk_control rwc = {
95 .rmap_one = page_idle_clear_pte_refs_one,
96 .anon_lock = folio_lock_anon_vma_read,
97 };
98 bool need_lock;
99
100 if (!folio_mapped(folio) || !folio_raw_mapping(folio))
101 return;
102
103 need_lock = !folio_test_anon(folio) || folio_test_ksm(folio);
104 if (need_lock && !folio_trylock(folio))
105 return;
106
107 rmap_walk(folio, &rwc);
108
109 if (need_lock)
110 folio_unlock(folio);
111}
112
113static ssize_t page_idle_bitmap_read(struct file *file, struct kobject *kobj,
114 struct bin_attribute *attr, char *buf,
115 loff_t pos, size_t count)
116{
117 u64 *out = (u64 *)buf;
118 struct page *page;
119 unsigned long pfn, end_pfn;
120 int bit;
121
122 if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE)
123 return -EINVAL;
124
125 pfn = pos * BITS_PER_BYTE;
126 if (pfn >= max_pfn)
127 return 0;
128
129 end_pfn = pfn + count * BITS_PER_BYTE;
130 if (end_pfn > max_pfn)
131 end_pfn = max_pfn;
132
133 for (; pfn < end_pfn; pfn++) {
134 bit = pfn % BITMAP_CHUNK_BITS;
135 if (!bit)
136 *out = 0ULL;
137 page = page_idle_get_page(pfn);
138 if (page) {
139 if (page_is_idle(page)) {
140 /*
141 * The page might have been referenced via a
142 * pte, in which case it is not idle. Clear
143 * refs and recheck.
144 */
145 page_idle_clear_pte_refs(page);
146 if (page_is_idle(page))
147 *out |= 1ULL << bit;
148 }
149 put_page(page);
150 }
151 if (bit == BITMAP_CHUNK_BITS - 1)
152 out++;
153 cond_resched();
154 }
155 return (char *)out - buf;
156}
157
158static ssize_t page_idle_bitmap_write(struct file *file, struct kobject *kobj,
159 struct bin_attribute *attr, char *buf,
160 loff_t pos, size_t count)
161{
162 const u64 *in = (u64 *)buf;
163 struct page *page;
164 unsigned long pfn, end_pfn;
165 int bit;
166
167 if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE)
168 return -EINVAL;
169
170 pfn = pos * BITS_PER_BYTE;
171 if (pfn >= max_pfn)
172 return -ENXIO;
173
174 end_pfn = pfn + count * BITS_PER_BYTE;
175 if (end_pfn > max_pfn)
176 end_pfn = max_pfn;
177
178 for (; pfn < end_pfn; pfn++) {
179 bit = pfn % BITMAP_CHUNK_BITS;
180 if ((*in >> bit) & 1) {
181 page = page_idle_get_page(pfn);
182 if (page) {
183 page_idle_clear_pte_refs(page);
184 set_page_idle(page);
185 put_page(page);
186 }
187 }
188 if (bit == BITMAP_CHUNK_BITS - 1)
189 in++;
190 cond_resched();
191 }
192 return (char *)in - buf;
193}
194
195static struct bin_attribute page_idle_bitmap_attr =
196 __BIN_ATTR(bitmap, 0600,
197 page_idle_bitmap_read, page_idle_bitmap_write, 0);
198
199static struct bin_attribute *page_idle_bin_attrs[] = {
200 &page_idle_bitmap_attr,
201 NULL,
202};
203
204static const struct attribute_group page_idle_attr_group = {
205 .bin_attrs = page_idle_bin_attrs,
206 .name = "page_idle",
207};
208
209static int __init page_idle_init(void)
210{
211 int err;
212
213 err = sysfs_create_group(mm_kobj, &page_idle_attr_group);
214 if (err) {
215 pr_err("page_idle: register sysfs failed\n");
216 return err;
217 }
218 return 0;
219}
220subsys_initcall(page_idle_init);