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))) { 64 pmd = page_check_address_pmd(page, mm, addr, 65 PAGE_CHECK_ADDRESS_PMD_FLAG, &ptl); 66 if (pmd) { 67 referenced = pmdp_clear_young_notify(vma, addr, pmd); 68 spin_unlock(ptl); 69 } 70 } else { 71 pte = page_check_address(page, mm, addr, &ptl, 0); 72 if (pte) { 73 referenced = ptep_clear_young_notify(vma, addr, pte); 74 pte_unmap_unlock(pte, ptl); 75 } 76 } 77 if (referenced) { 78 clear_page_idle(page); 79 /* 80 * We cleared the referenced bit in a mapping to this page. To 81 * avoid interference with page reclaim, mark it young so that 82 * page_referenced() will return > 0. 83 */ 84 set_page_young(page); 85 } 86 return SWAP_AGAIN; 87 } 88 89 static void page_idle_clear_pte_refs(struct page *page) 90 { 91 /* 92 * Since rwc.arg is unused, rwc is effectively immutable, so we 93 * can make it static const to save some cycles and stack. 94 */ 95 static const struct rmap_walk_control rwc = { 96 .rmap_one = page_idle_clear_pte_refs_one, 97 .anon_lock = page_lock_anon_vma_read, 98 }; 99 bool need_lock; 100 101 if (!page_mapped(page) || 102 !page_rmapping(page)) 103 return; 104 105 need_lock = !PageAnon(page) || PageKsm(page); 106 if (need_lock && !trylock_page(page)) 107 return; 108 109 rmap_walk(page, (struct rmap_walk_control *)&rwc); 110 111 if (need_lock) 112 unlock_page(page); 113 } 114 115 static ssize_t page_idle_bitmap_read(struct file *file, struct kobject *kobj, 116 struct bin_attribute *attr, char *buf, 117 loff_t pos, size_t count) 118 { 119 u64 *out = (u64 *)buf; 120 struct page *page; 121 unsigned long pfn, end_pfn; 122 int bit; 123 124 if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE) 125 return -EINVAL; 126 127 pfn = pos * BITS_PER_BYTE; 128 if (pfn >= max_pfn) 129 return 0; 130 131 end_pfn = pfn + count * BITS_PER_BYTE; 132 if (end_pfn > max_pfn) 133 end_pfn = ALIGN(max_pfn, BITMAP_CHUNK_BITS); 134 135 for (; pfn < end_pfn; pfn++) { 136 bit = pfn % BITMAP_CHUNK_BITS; 137 if (!bit) 138 *out = 0ULL; 139 page = page_idle_get_page(pfn); 140 if (page) { 141 if (page_is_idle(page)) { 142 /* 143 * The page might have been referenced via a 144 * pte, in which case it is not idle. Clear 145 * refs and recheck. 146 */ 147 page_idle_clear_pte_refs(page); 148 if (page_is_idle(page)) 149 *out |= 1ULL << bit; 150 } 151 put_page(page); 152 } 153 if (bit == BITMAP_CHUNK_BITS - 1) 154 out++; 155 cond_resched(); 156 } 157 return (char *)out - buf; 158 } 159 160 static ssize_t page_idle_bitmap_write(struct file *file, struct kobject *kobj, 161 struct bin_attribute *attr, char *buf, 162 loff_t pos, size_t count) 163 { 164 const u64 *in = (u64 *)buf; 165 struct page *page; 166 unsigned long pfn, end_pfn; 167 int bit; 168 169 if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE) 170 return -EINVAL; 171 172 pfn = pos * BITS_PER_BYTE; 173 if (pfn >= max_pfn) 174 return -ENXIO; 175 176 end_pfn = pfn + count * BITS_PER_BYTE; 177 if (end_pfn > max_pfn) 178 end_pfn = ALIGN(max_pfn, BITMAP_CHUNK_BITS); 179 180 for (; pfn < end_pfn; pfn++) { 181 bit = pfn % BITMAP_CHUNK_BITS; 182 if ((*in >> bit) & 1) { 183 page = page_idle_get_page(pfn); 184 if (page) { 185 page_idle_clear_pte_refs(page); 186 set_page_idle(page); 187 put_page(page); 188 } 189 } 190 if (bit == BITMAP_CHUNK_BITS - 1) 191 in++; 192 cond_resched(); 193 } 194 return (char *)in - buf; 195 } 196 197 static struct bin_attribute page_idle_bitmap_attr = 198 __BIN_ATTR(bitmap, S_IRUSR | S_IWUSR, 199 page_idle_bitmap_read, page_idle_bitmap_write, 0); 200 201 static struct bin_attribute *page_idle_bin_attrs[] = { 202 &page_idle_bitmap_attr, 203 NULL, 204 }; 205 206 static struct attribute_group page_idle_attr_group = { 207 .bin_attrs = page_idle_bin_attrs, 208 .name = "page_idle", 209 }; 210 211 #ifndef CONFIG_64BIT 212 static bool need_page_idle(void) 213 { 214 return true; 215 } 216 struct page_ext_operations page_idle_ops = { 217 .need = need_page_idle, 218 }; 219 #endif 220 221 static int __init page_idle_init(void) 222 { 223 int err; 224 225 err = sysfs_create_group(mm_kobj, &page_idle_attr_group); 226 if (err) { 227 pr_err("page_idle: register sysfs failed\n"); 228 return err; 229 } 230 return 0; 231 } 232 subsys_initcall(page_idle_init); 233