Kirill A. Shutemov | b46e756 | 2016-07-26 15:26:24 -0700 | [diff] [blame] | 1 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| 2 | |
| 3 | #include <linux/mm.h> |
| 4 | #include <linux/sched.h> |
| 5 | #include <linux/mmu_notifier.h> |
| 6 | #include <linux/rmap.h> |
| 7 | #include <linux/swap.h> |
| 8 | #include <linux/mm_inline.h> |
| 9 | #include <linux/kthread.h> |
| 10 | #include <linux/khugepaged.h> |
| 11 | #include <linux/freezer.h> |
| 12 | #include <linux/mman.h> |
| 13 | #include <linux/hashtable.h> |
| 14 | #include <linux/userfaultfd_k.h> |
| 15 | #include <linux/page_idle.h> |
| 16 | #include <linux/swapops.h> |
| 17 | |
| 18 | #include <asm/tlb.h> |
| 19 | #include <asm/pgalloc.h> |
| 20 | #include "internal.h" |
| 21 | |
| 22 | enum scan_result { |
| 23 | SCAN_FAIL, |
| 24 | SCAN_SUCCEED, |
| 25 | SCAN_PMD_NULL, |
| 26 | SCAN_EXCEED_NONE_PTE, |
| 27 | SCAN_PTE_NON_PRESENT, |
| 28 | SCAN_PAGE_RO, |
| 29 | SCAN_NO_REFERENCED_PAGE, |
| 30 | SCAN_PAGE_NULL, |
| 31 | SCAN_SCAN_ABORT, |
| 32 | SCAN_PAGE_COUNT, |
| 33 | SCAN_PAGE_LRU, |
| 34 | SCAN_PAGE_LOCK, |
| 35 | SCAN_PAGE_ANON, |
| 36 | SCAN_PAGE_COMPOUND, |
| 37 | SCAN_ANY_PROCESS, |
| 38 | SCAN_VMA_NULL, |
| 39 | SCAN_VMA_CHECK, |
| 40 | SCAN_ADDRESS_RANGE, |
| 41 | SCAN_SWAP_CACHE_PAGE, |
| 42 | SCAN_DEL_PAGE_LRU, |
| 43 | SCAN_ALLOC_HUGE_PAGE_FAIL, |
| 44 | SCAN_CGROUP_CHARGE_FAIL, |
| 45 | SCAN_EXCEED_SWAP_PTE |
| 46 | }; |
| 47 | |
| 48 | #define CREATE_TRACE_POINTS |
| 49 | #include <trace/events/huge_memory.h> |
| 50 | |
| 51 | /* default scan 8*512 pte (or vmas) every 30 second */ |
| 52 | static unsigned int khugepaged_pages_to_scan __read_mostly; |
| 53 | static unsigned int khugepaged_pages_collapsed; |
| 54 | static unsigned int khugepaged_full_scans; |
| 55 | static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000; |
| 56 | /* during fragmentation poll the hugepage allocator once every minute */ |
| 57 | static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000; |
| 58 | static unsigned long khugepaged_sleep_expire; |
| 59 | static DEFINE_SPINLOCK(khugepaged_mm_lock); |
| 60 | static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); |
| 61 | /* |
| 62 | * default collapse hugepages if there is at least one pte mapped like |
| 63 | * it would have happened if the vma was large enough during page |
| 64 | * fault. |
| 65 | */ |
| 66 | static unsigned int khugepaged_max_ptes_none __read_mostly; |
| 67 | static unsigned int khugepaged_max_ptes_swap __read_mostly; |
| 68 | |
| 69 | #define MM_SLOTS_HASH_BITS 10 |
| 70 | static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); |
| 71 | |
| 72 | static struct kmem_cache *mm_slot_cache __read_mostly; |
| 73 | |
| 74 | /** |
| 75 | * struct mm_slot - hash lookup from mm to mm_slot |
| 76 | * @hash: hash collision list |
| 77 | * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head |
| 78 | * @mm: the mm that this information is valid for |
| 79 | */ |
| 80 | struct mm_slot { |
| 81 | struct hlist_node hash; |
| 82 | struct list_head mm_node; |
| 83 | struct mm_struct *mm; |
| 84 | }; |
| 85 | |
| 86 | /** |
| 87 | * struct khugepaged_scan - cursor for scanning |
| 88 | * @mm_head: the head of the mm list to scan |
| 89 | * @mm_slot: the current mm_slot we are scanning |
| 90 | * @address: the next address inside that to be scanned |
| 91 | * |
| 92 | * There is only the one khugepaged_scan instance of this cursor structure. |
| 93 | */ |
| 94 | struct khugepaged_scan { |
| 95 | struct list_head mm_head; |
| 96 | struct mm_slot *mm_slot; |
| 97 | unsigned long address; |
| 98 | }; |
| 99 | |
| 100 | static struct khugepaged_scan khugepaged_scan = { |
| 101 | .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head), |
| 102 | }; |
| 103 | |
| 104 | static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, |
| 105 | struct kobj_attribute *attr, |
| 106 | char *buf) |
| 107 | { |
| 108 | return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs); |
| 109 | } |
| 110 | |
| 111 | static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, |
| 112 | struct kobj_attribute *attr, |
| 113 | const char *buf, size_t count) |
| 114 | { |
| 115 | unsigned long msecs; |
| 116 | int err; |
| 117 | |
| 118 | err = kstrtoul(buf, 10, &msecs); |
| 119 | if (err || msecs > UINT_MAX) |
| 120 | return -EINVAL; |
| 121 | |
| 122 | khugepaged_scan_sleep_millisecs = msecs; |
| 123 | khugepaged_sleep_expire = 0; |
| 124 | wake_up_interruptible(&khugepaged_wait); |
| 125 | |
| 126 | return count; |
| 127 | } |
| 128 | static struct kobj_attribute scan_sleep_millisecs_attr = |
| 129 | __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show, |
| 130 | scan_sleep_millisecs_store); |
| 131 | |
| 132 | static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj, |
| 133 | struct kobj_attribute *attr, |
| 134 | char *buf) |
| 135 | { |
| 136 | return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs); |
| 137 | } |
| 138 | |
| 139 | static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, |
| 140 | struct kobj_attribute *attr, |
| 141 | const char *buf, size_t count) |
| 142 | { |
| 143 | unsigned long msecs; |
| 144 | int err; |
| 145 | |
| 146 | err = kstrtoul(buf, 10, &msecs); |
| 147 | if (err || msecs > UINT_MAX) |
| 148 | return -EINVAL; |
| 149 | |
| 150 | khugepaged_alloc_sleep_millisecs = msecs; |
| 151 | khugepaged_sleep_expire = 0; |
| 152 | wake_up_interruptible(&khugepaged_wait); |
| 153 | |
| 154 | return count; |
| 155 | } |
| 156 | static struct kobj_attribute alloc_sleep_millisecs_attr = |
| 157 | __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show, |
| 158 | alloc_sleep_millisecs_store); |
| 159 | |
| 160 | static ssize_t pages_to_scan_show(struct kobject *kobj, |
| 161 | struct kobj_attribute *attr, |
| 162 | char *buf) |
| 163 | { |
| 164 | return sprintf(buf, "%u\n", khugepaged_pages_to_scan); |
| 165 | } |
| 166 | static ssize_t pages_to_scan_store(struct kobject *kobj, |
| 167 | struct kobj_attribute *attr, |
| 168 | const char *buf, size_t count) |
| 169 | { |
| 170 | int err; |
| 171 | unsigned long pages; |
| 172 | |
| 173 | err = kstrtoul(buf, 10, &pages); |
| 174 | if (err || !pages || pages > UINT_MAX) |
| 175 | return -EINVAL; |
| 176 | |
| 177 | khugepaged_pages_to_scan = pages; |
| 178 | |
| 179 | return count; |
| 180 | } |
| 181 | static struct kobj_attribute pages_to_scan_attr = |
| 182 | __ATTR(pages_to_scan, 0644, pages_to_scan_show, |
| 183 | pages_to_scan_store); |
| 184 | |
| 185 | static ssize_t pages_collapsed_show(struct kobject *kobj, |
| 186 | struct kobj_attribute *attr, |
| 187 | char *buf) |
| 188 | { |
| 189 | return sprintf(buf, "%u\n", khugepaged_pages_collapsed); |
| 190 | } |
| 191 | static struct kobj_attribute pages_collapsed_attr = |
| 192 | __ATTR_RO(pages_collapsed); |
| 193 | |
| 194 | static ssize_t full_scans_show(struct kobject *kobj, |
| 195 | struct kobj_attribute *attr, |
| 196 | char *buf) |
| 197 | { |
| 198 | return sprintf(buf, "%u\n", khugepaged_full_scans); |
| 199 | } |
| 200 | static struct kobj_attribute full_scans_attr = |
| 201 | __ATTR_RO(full_scans); |
| 202 | |
| 203 | static ssize_t khugepaged_defrag_show(struct kobject *kobj, |
| 204 | struct kobj_attribute *attr, char *buf) |
| 205 | { |
| 206 | return single_hugepage_flag_show(kobj, attr, buf, |
| 207 | TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); |
| 208 | } |
| 209 | static ssize_t khugepaged_defrag_store(struct kobject *kobj, |
| 210 | struct kobj_attribute *attr, |
| 211 | const char *buf, size_t count) |
| 212 | { |
| 213 | return single_hugepage_flag_store(kobj, attr, buf, count, |
| 214 | TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); |
| 215 | } |
| 216 | static struct kobj_attribute khugepaged_defrag_attr = |
| 217 | __ATTR(defrag, 0644, khugepaged_defrag_show, |
| 218 | khugepaged_defrag_store); |
| 219 | |
| 220 | /* |
| 221 | * max_ptes_none controls if khugepaged should collapse hugepages over |
| 222 | * any unmapped ptes in turn potentially increasing the memory |
| 223 | * footprint of the vmas. When max_ptes_none is 0 khugepaged will not |
| 224 | * reduce the available free memory in the system as it |
| 225 | * runs. Increasing max_ptes_none will instead potentially reduce the |
| 226 | * free memory in the system during the khugepaged scan. |
| 227 | */ |
| 228 | static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj, |
| 229 | struct kobj_attribute *attr, |
| 230 | char *buf) |
| 231 | { |
| 232 | return sprintf(buf, "%u\n", khugepaged_max_ptes_none); |
| 233 | } |
| 234 | static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj, |
| 235 | struct kobj_attribute *attr, |
| 236 | const char *buf, size_t count) |
| 237 | { |
| 238 | int err; |
| 239 | unsigned long max_ptes_none; |
| 240 | |
| 241 | err = kstrtoul(buf, 10, &max_ptes_none); |
| 242 | if (err || max_ptes_none > HPAGE_PMD_NR-1) |
| 243 | return -EINVAL; |
| 244 | |
| 245 | khugepaged_max_ptes_none = max_ptes_none; |
| 246 | |
| 247 | return count; |
| 248 | } |
| 249 | static struct kobj_attribute khugepaged_max_ptes_none_attr = |
| 250 | __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show, |
| 251 | khugepaged_max_ptes_none_store); |
| 252 | |
| 253 | static ssize_t khugepaged_max_ptes_swap_show(struct kobject *kobj, |
| 254 | struct kobj_attribute *attr, |
| 255 | char *buf) |
| 256 | { |
| 257 | return sprintf(buf, "%u\n", khugepaged_max_ptes_swap); |
| 258 | } |
| 259 | |
| 260 | static ssize_t khugepaged_max_ptes_swap_store(struct kobject *kobj, |
| 261 | struct kobj_attribute *attr, |
| 262 | const char *buf, size_t count) |
| 263 | { |
| 264 | int err; |
| 265 | unsigned long max_ptes_swap; |
| 266 | |
| 267 | err = kstrtoul(buf, 10, &max_ptes_swap); |
| 268 | if (err || max_ptes_swap > HPAGE_PMD_NR-1) |
| 269 | return -EINVAL; |
| 270 | |
| 271 | khugepaged_max_ptes_swap = max_ptes_swap; |
| 272 | |
| 273 | return count; |
| 274 | } |
| 275 | |
| 276 | static struct kobj_attribute khugepaged_max_ptes_swap_attr = |
| 277 | __ATTR(max_ptes_swap, 0644, khugepaged_max_ptes_swap_show, |
| 278 | khugepaged_max_ptes_swap_store); |
| 279 | |
| 280 | static struct attribute *khugepaged_attr[] = { |
| 281 | &khugepaged_defrag_attr.attr, |
| 282 | &khugepaged_max_ptes_none_attr.attr, |
| 283 | &pages_to_scan_attr.attr, |
| 284 | &pages_collapsed_attr.attr, |
| 285 | &full_scans_attr.attr, |
| 286 | &scan_sleep_millisecs_attr.attr, |
| 287 | &alloc_sleep_millisecs_attr.attr, |
| 288 | &khugepaged_max_ptes_swap_attr.attr, |
| 289 | NULL, |
| 290 | }; |
| 291 | |
| 292 | struct attribute_group khugepaged_attr_group = { |
| 293 | .attrs = khugepaged_attr, |
| 294 | .name = "khugepaged", |
| 295 | }; |
| 296 | |
| 297 | #define VM_NO_KHUGEPAGED (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE) |
| 298 | |
| 299 | int hugepage_madvise(struct vm_area_struct *vma, |
| 300 | unsigned long *vm_flags, int advice) |
| 301 | { |
| 302 | switch (advice) { |
| 303 | case MADV_HUGEPAGE: |
| 304 | #ifdef CONFIG_S390 |
| 305 | /* |
| 306 | * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390 |
| 307 | * can't handle this properly after s390_enable_sie, so we simply |
| 308 | * ignore the madvise to prevent qemu from causing a SIGSEGV. |
| 309 | */ |
| 310 | if (mm_has_pgste(vma->vm_mm)) |
| 311 | return 0; |
| 312 | #endif |
| 313 | *vm_flags &= ~VM_NOHUGEPAGE; |
| 314 | *vm_flags |= VM_HUGEPAGE; |
| 315 | /* |
| 316 | * If the vma become good for khugepaged to scan, |
| 317 | * register it here without waiting a page fault that |
| 318 | * may not happen any time soon. |
| 319 | */ |
| 320 | if (!(*vm_flags & VM_NO_KHUGEPAGED) && |
| 321 | khugepaged_enter_vma_merge(vma, *vm_flags)) |
| 322 | return -ENOMEM; |
| 323 | break; |
| 324 | case MADV_NOHUGEPAGE: |
| 325 | *vm_flags &= ~VM_HUGEPAGE; |
| 326 | *vm_flags |= VM_NOHUGEPAGE; |
| 327 | /* |
| 328 | * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning |
| 329 | * this vma even if we leave the mm registered in khugepaged if |
| 330 | * it got registered before VM_NOHUGEPAGE was set. |
| 331 | */ |
| 332 | break; |
| 333 | } |
| 334 | |
| 335 | return 0; |
| 336 | } |
| 337 | |
| 338 | int __init khugepaged_init(void) |
| 339 | { |
| 340 | mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", |
| 341 | sizeof(struct mm_slot), |
| 342 | __alignof__(struct mm_slot), 0, NULL); |
| 343 | if (!mm_slot_cache) |
| 344 | return -ENOMEM; |
| 345 | |
| 346 | khugepaged_pages_to_scan = HPAGE_PMD_NR * 8; |
| 347 | khugepaged_max_ptes_none = HPAGE_PMD_NR - 1; |
| 348 | khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8; |
| 349 | |
| 350 | return 0; |
| 351 | } |
| 352 | |
| 353 | void __init khugepaged_destroy(void) |
| 354 | { |
| 355 | kmem_cache_destroy(mm_slot_cache); |
| 356 | } |
| 357 | |
| 358 | static inline struct mm_slot *alloc_mm_slot(void) |
| 359 | { |
| 360 | if (!mm_slot_cache) /* initialization failed */ |
| 361 | return NULL; |
| 362 | return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); |
| 363 | } |
| 364 | |
| 365 | static inline void free_mm_slot(struct mm_slot *mm_slot) |
| 366 | { |
| 367 | kmem_cache_free(mm_slot_cache, mm_slot); |
| 368 | } |
| 369 | |
| 370 | static struct mm_slot *get_mm_slot(struct mm_struct *mm) |
| 371 | { |
| 372 | struct mm_slot *mm_slot; |
| 373 | |
| 374 | hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm) |
| 375 | if (mm == mm_slot->mm) |
| 376 | return mm_slot; |
| 377 | |
| 378 | return NULL; |
| 379 | } |
| 380 | |
| 381 | static void insert_to_mm_slots_hash(struct mm_struct *mm, |
| 382 | struct mm_slot *mm_slot) |
| 383 | { |
| 384 | mm_slot->mm = mm; |
| 385 | hash_add(mm_slots_hash, &mm_slot->hash, (long)mm); |
| 386 | } |
| 387 | |
| 388 | static inline int khugepaged_test_exit(struct mm_struct *mm) |
| 389 | { |
| 390 | return atomic_read(&mm->mm_users) == 0; |
| 391 | } |
| 392 | |
| 393 | int __khugepaged_enter(struct mm_struct *mm) |
| 394 | { |
| 395 | struct mm_slot *mm_slot; |
| 396 | int wakeup; |
| 397 | |
| 398 | mm_slot = alloc_mm_slot(); |
| 399 | if (!mm_slot) |
| 400 | return -ENOMEM; |
| 401 | |
| 402 | /* __khugepaged_exit() must not run from under us */ |
| 403 | VM_BUG_ON_MM(khugepaged_test_exit(mm), mm); |
| 404 | if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { |
| 405 | free_mm_slot(mm_slot); |
| 406 | return 0; |
| 407 | } |
| 408 | |
| 409 | spin_lock(&khugepaged_mm_lock); |
| 410 | insert_to_mm_slots_hash(mm, mm_slot); |
| 411 | /* |
| 412 | * Insert just behind the scanning cursor, to let the area settle |
| 413 | * down a little. |
| 414 | */ |
| 415 | wakeup = list_empty(&khugepaged_scan.mm_head); |
| 416 | list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); |
| 417 | spin_unlock(&khugepaged_mm_lock); |
| 418 | |
| 419 | atomic_inc(&mm->mm_count); |
| 420 | if (wakeup) |
| 421 | wake_up_interruptible(&khugepaged_wait); |
| 422 | |
| 423 | return 0; |
| 424 | } |
| 425 | |
| 426 | int khugepaged_enter_vma_merge(struct vm_area_struct *vma, |
| 427 | unsigned long vm_flags) |
| 428 | { |
| 429 | unsigned long hstart, hend; |
| 430 | if (!vma->anon_vma) |
| 431 | /* |
| 432 | * Not yet faulted in so we will register later in the |
| 433 | * page fault if needed. |
| 434 | */ |
| 435 | return 0; |
| 436 | if (vma->vm_ops || (vm_flags & VM_NO_KHUGEPAGED)) |
| 437 | /* khugepaged not yet working on file or special mappings */ |
| 438 | return 0; |
| 439 | hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; |
| 440 | hend = vma->vm_end & HPAGE_PMD_MASK; |
| 441 | if (hstart < hend) |
| 442 | return khugepaged_enter(vma, vm_flags); |
| 443 | return 0; |
| 444 | } |
| 445 | |
| 446 | void __khugepaged_exit(struct mm_struct *mm) |
| 447 | { |
| 448 | struct mm_slot *mm_slot; |
| 449 | int free = 0; |
| 450 | |
| 451 | spin_lock(&khugepaged_mm_lock); |
| 452 | mm_slot = get_mm_slot(mm); |
| 453 | if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { |
| 454 | hash_del(&mm_slot->hash); |
| 455 | list_del(&mm_slot->mm_node); |
| 456 | free = 1; |
| 457 | } |
| 458 | spin_unlock(&khugepaged_mm_lock); |
| 459 | |
| 460 | if (free) { |
| 461 | clear_bit(MMF_VM_HUGEPAGE, &mm->flags); |
| 462 | free_mm_slot(mm_slot); |
| 463 | mmdrop(mm); |
| 464 | } else if (mm_slot) { |
| 465 | /* |
| 466 | * This is required to serialize against |
| 467 | * khugepaged_test_exit() (which is guaranteed to run |
| 468 | * under mmap sem read mode). Stop here (after we |
| 469 | * return all pagetables will be destroyed) until |
| 470 | * khugepaged has finished working on the pagetables |
| 471 | * under the mmap_sem. |
| 472 | */ |
| 473 | down_write(&mm->mmap_sem); |
| 474 | up_write(&mm->mmap_sem); |
| 475 | } |
| 476 | } |
| 477 | |
| 478 | static void release_pte_page(struct page *page) |
| 479 | { |
| 480 | /* 0 stands for page_is_file_cache(page) == false */ |
| 481 | dec_zone_page_state(page, NR_ISOLATED_ANON + 0); |
| 482 | unlock_page(page); |
| 483 | putback_lru_page(page); |
| 484 | } |
| 485 | |
| 486 | static void release_pte_pages(pte_t *pte, pte_t *_pte) |
| 487 | { |
| 488 | while (--_pte >= pte) { |
| 489 | pte_t pteval = *_pte; |
| 490 | if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval))) |
| 491 | release_pte_page(pte_page(pteval)); |
| 492 | } |
| 493 | } |
| 494 | |
| 495 | static int __collapse_huge_page_isolate(struct vm_area_struct *vma, |
| 496 | unsigned long address, |
| 497 | pte_t *pte) |
| 498 | { |
| 499 | struct page *page = NULL; |
| 500 | pte_t *_pte; |
| 501 | int none_or_zero = 0, result = 0; |
| 502 | bool referenced = false, writable = false; |
| 503 | |
| 504 | for (_pte = pte; _pte < pte+HPAGE_PMD_NR; |
| 505 | _pte++, address += PAGE_SIZE) { |
| 506 | pte_t pteval = *_pte; |
| 507 | if (pte_none(pteval) || (pte_present(pteval) && |
| 508 | is_zero_pfn(pte_pfn(pteval)))) { |
| 509 | if (!userfaultfd_armed(vma) && |
| 510 | ++none_or_zero <= khugepaged_max_ptes_none) { |
| 511 | continue; |
| 512 | } else { |
| 513 | result = SCAN_EXCEED_NONE_PTE; |
| 514 | goto out; |
| 515 | } |
| 516 | } |
| 517 | if (!pte_present(pteval)) { |
| 518 | result = SCAN_PTE_NON_PRESENT; |
| 519 | goto out; |
| 520 | } |
| 521 | page = vm_normal_page(vma, address, pteval); |
| 522 | if (unlikely(!page)) { |
| 523 | result = SCAN_PAGE_NULL; |
| 524 | goto out; |
| 525 | } |
| 526 | |
| 527 | VM_BUG_ON_PAGE(PageCompound(page), page); |
| 528 | VM_BUG_ON_PAGE(!PageAnon(page), page); |
| 529 | VM_BUG_ON_PAGE(!PageSwapBacked(page), page); |
| 530 | |
| 531 | /* |
| 532 | * We can do it before isolate_lru_page because the |
| 533 | * page can't be freed from under us. NOTE: PG_lock |
| 534 | * is needed to serialize against split_huge_page |
| 535 | * when invoked from the VM. |
| 536 | */ |
| 537 | if (!trylock_page(page)) { |
| 538 | result = SCAN_PAGE_LOCK; |
| 539 | goto out; |
| 540 | } |
| 541 | |
| 542 | /* |
| 543 | * cannot use mapcount: can't collapse if there's a gup pin. |
| 544 | * The page must only be referenced by the scanned process |
| 545 | * and page swap cache. |
| 546 | */ |
| 547 | if (page_count(page) != 1 + !!PageSwapCache(page)) { |
| 548 | unlock_page(page); |
| 549 | result = SCAN_PAGE_COUNT; |
| 550 | goto out; |
| 551 | } |
| 552 | if (pte_write(pteval)) { |
| 553 | writable = true; |
| 554 | } else { |
| 555 | if (PageSwapCache(page) && |
| 556 | !reuse_swap_page(page, NULL)) { |
| 557 | unlock_page(page); |
| 558 | result = SCAN_SWAP_CACHE_PAGE; |
| 559 | goto out; |
| 560 | } |
| 561 | /* |
| 562 | * Page is not in the swap cache. It can be collapsed |
| 563 | * into a THP. |
| 564 | */ |
| 565 | } |
| 566 | |
| 567 | /* |
| 568 | * Isolate the page to avoid collapsing an hugepage |
| 569 | * currently in use by the VM. |
| 570 | */ |
| 571 | if (isolate_lru_page(page)) { |
| 572 | unlock_page(page); |
| 573 | result = SCAN_DEL_PAGE_LRU; |
| 574 | goto out; |
| 575 | } |
| 576 | /* 0 stands for page_is_file_cache(page) == false */ |
| 577 | inc_zone_page_state(page, NR_ISOLATED_ANON + 0); |
| 578 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
| 579 | VM_BUG_ON_PAGE(PageLRU(page), page); |
| 580 | |
| 581 | /* If there is no mapped pte young don't collapse the page */ |
| 582 | if (pte_young(pteval) || |
| 583 | page_is_young(page) || PageReferenced(page) || |
| 584 | mmu_notifier_test_young(vma->vm_mm, address)) |
| 585 | referenced = true; |
| 586 | } |
| 587 | if (likely(writable)) { |
| 588 | if (likely(referenced)) { |
| 589 | result = SCAN_SUCCEED; |
| 590 | trace_mm_collapse_huge_page_isolate(page, none_or_zero, |
| 591 | referenced, writable, result); |
| 592 | return 1; |
| 593 | } |
| 594 | } else { |
| 595 | result = SCAN_PAGE_RO; |
| 596 | } |
| 597 | |
| 598 | out: |
| 599 | release_pte_pages(pte, _pte); |
| 600 | trace_mm_collapse_huge_page_isolate(page, none_or_zero, |
| 601 | referenced, writable, result); |
| 602 | return 0; |
| 603 | } |
| 604 | |
| 605 | static void __collapse_huge_page_copy(pte_t *pte, struct page *page, |
| 606 | struct vm_area_struct *vma, |
| 607 | unsigned long address, |
| 608 | spinlock_t *ptl) |
| 609 | { |
| 610 | pte_t *_pte; |
| 611 | for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) { |
| 612 | pte_t pteval = *_pte; |
| 613 | struct page *src_page; |
| 614 | |
| 615 | if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { |
| 616 | clear_user_highpage(page, address); |
| 617 | add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); |
| 618 | if (is_zero_pfn(pte_pfn(pteval))) { |
| 619 | /* |
| 620 | * ptl mostly unnecessary. |
| 621 | */ |
| 622 | spin_lock(ptl); |
| 623 | /* |
| 624 | * paravirt calls inside pte_clear here are |
| 625 | * superfluous. |
| 626 | */ |
| 627 | pte_clear(vma->vm_mm, address, _pte); |
| 628 | spin_unlock(ptl); |
| 629 | } |
| 630 | } else { |
| 631 | src_page = pte_page(pteval); |
| 632 | copy_user_highpage(page, src_page, address, vma); |
| 633 | VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page); |
| 634 | release_pte_page(src_page); |
| 635 | /* |
| 636 | * ptl mostly unnecessary, but preempt has to |
| 637 | * be disabled to update the per-cpu stats |
| 638 | * inside page_remove_rmap(). |
| 639 | */ |
| 640 | spin_lock(ptl); |
| 641 | /* |
| 642 | * paravirt calls inside pte_clear here are |
| 643 | * superfluous. |
| 644 | */ |
| 645 | pte_clear(vma->vm_mm, address, _pte); |
| 646 | page_remove_rmap(src_page, false); |
| 647 | spin_unlock(ptl); |
| 648 | free_page_and_swap_cache(src_page); |
| 649 | } |
| 650 | |
| 651 | address += PAGE_SIZE; |
| 652 | page++; |
| 653 | } |
| 654 | } |
| 655 | |
| 656 | static void khugepaged_alloc_sleep(void) |
| 657 | { |
| 658 | DEFINE_WAIT(wait); |
| 659 | |
| 660 | add_wait_queue(&khugepaged_wait, &wait); |
| 661 | freezable_schedule_timeout_interruptible( |
| 662 | msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); |
| 663 | remove_wait_queue(&khugepaged_wait, &wait); |
| 664 | } |
| 665 | |
| 666 | static int khugepaged_node_load[MAX_NUMNODES]; |
| 667 | |
| 668 | static bool khugepaged_scan_abort(int nid) |
| 669 | { |
| 670 | int i; |
| 671 | |
| 672 | /* |
| 673 | * If zone_reclaim_mode is disabled, then no extra effort is made to |
| 674 | * allocate memory locally. |
| 675 | */ |
| 676 | if (!zone_reclaim_mode) |
| 677 | return false; |
| 678 | |
| 679 | /* If there is a count for this node already, it must be acceptable */ |
| 680 | if (khugepaged_node_load[nid]) |
| 681 | return false; |
| 682 | |
| 683 | for (i = 0; i < MAX_NUMNODES; i++) { |
| 684 | if (!khugepaged_node_load[i]) |
| 685 | continue; |
| 686 | if (node_distance(nid, i) > RECLAIM_DISTANCE) |
| 687 | return true; |
| 688 | } |
| 689 | return false; |
| 690 | } |
| 691 | |
| 692 | /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */ |
| 693 | static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void) |
| 694 | { |
| 695 | return GFP_TRANSHUGE | (khugepaged_defrag() ? __GFP_DIRECT_RECLAIM : 0); |
| 696 | } |
| 697 | |
| 698 | #ifdef CONFIG_NUMA |
| 699 | static int khugepaged_find_target_node(void) |
| 700 | { |
| 701 | static int last_khugepaged_target_node = NUMA_NO_NODE; |
| 702 | int nid, target_node = 0, max_value = 0; |
| 703 | |
| 704 | /* find first node with max normal pages hit */ |
| 705 | for (nid = 0; nid < MAX_NUMNODES; nid++) |
| 706 | if (khugepaged_node_load[nid] > max_value) { |
| 707 | max_value = khugepaged_node_load[nid]; |
| 708 | target_node = nid; |
| 709 | } |
| 710 | |
| 711 | /* do some balance if several nodes have the same hit record */ |
| 712 | if (target_node <= last_khugepaged_target_node) |
| 713 | for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES; |
| 714 | nid++) |
| 715 | if (max_value == khugepaged_node_load[nid]) { |
| 716 | target_node = nid; |
| 717 | break; |
| 718 | } |
| 719 | |
| 720 | last_khugepaged_target_node = target_node; |
| 721 | return target_node; |
| 722 | } |
| 723 | |
| 724 | static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) |
| 725 | { |
| 726 | if (IS_ERR(*hpage)) { |
| 727 | if (!*wait) |
| 728 | return false; |
| 729 | |
| 730 | *wait = false; |
| 731 | *hpage = NULL; |
| 732 | khugepaged_alloc_sleep(); |
| 733 | } else if (*hpage) { |
| 734 | put_page(*hpage); |
| 735 | *hpage = NULL; |
| 736 | } |
| 737 | |
| 738 | return true; |
| 739 | } |
| 740 | |
| 741 | static struct page * |
Kirill A. Shutemov | 988ddb7 | 2016-07-26 15:26:26 -0700 | [diff] [blame^] | 742 | khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node) |
Kirill A. Shutemov | b46e756 | 2016-07-26 15:26:24 -0700 | [diff] [blame] | 743 | { |
| 744 | VM_BUG_ON_PAGE(*hpage, *hpage); |
| 745 | |
Kirill A. Shutemov | b46e756 | 2016-07-26 15:26:24 -0700 | [diff] [blame] | 746 | *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER); |
| 747 | if (unlikely(!*hpage)) { |
| 748 | count_vm_event(THP_COLLAPSE_ALLOC_FAILED); |
| 749 | *hpage = ERR_PTR(-ENOMEM); |
| 750 | return NULL; |
| 751 | } |
| 752 | |
| 753 | prep_transhuge_page(*hpage); |
| 754 | count_vm_event(THP_COLLAPSE_ALLOC); |
| 755 | return *hpage; |
| 756 | } |
| 757 | #else |
| 758 | static int khugepaged_find_target_node(void) |
| 759 | { |
| 760 | return 0; |
| 761 | } |
| 762 | |
| 763 | static inline struct page *alloc_khugepaged_hugepage(void) |
| 764 | { |
| 765 | struct page *page; |
| 766 | |
| 767 | page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(), |
| 768 | HPAGE_PMD_ORDER); |
| 769 | if (page) |
| 770 | prep_transhuge_page(page); |
| 771 | return page; |
| 772 | } |
| 773 | |
| 774 | static struct page *khugepaged_alloc_hugepage(bool *wait) |
| 775 | { |
| 776 | struct page *hpage; |
| 777 | |
| 778 | do { |
| 779 | hpage = alloc_khugepaged_hugepage(); |
| 780 | if (!hpage) { |
| 781 | count_vm_event(THP_COLLAPSE_ALLOC_FAILED); |
| 782 | if (!*wait) |
| 783 | return NULL; |
| 784 | |
| 785 | *wait = false; |
| 786 | khugepaged_alloc_sleep(); |
| 787 | } else |
| 788 | count_vm_event(THP_COLLAPSE_ALLOC); |
| 789 | } while (unlikely(!hpage) && likely(khugepaged_enabled())); |
| 790 | |
| 791 | return hpage; |
| 792 | } |
| 793 | |
| 794 | static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) |
| 795 | { |
| 796 | if (!*hpage) |
| 797 | *hpage = khugepaged_alloc_hugepage(wait); |
| 798 | |
| 799 | if (unlikely(!*hpage)) |
| 800 | return false; |
| 801 | |
| 802 | return true; |
| 803 | } |
| 804 | |
| 805 | static struct page * |
Kirill A. Shutemov | 988ddb7 | 2016-07-26 15:26:26 -0700 | [diff] [blame^] | 806 | khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node) |
Kirill A. Shutemov | b46e756 | 2016-07-26 15:26:24 -0700 | [diff] [blame] | 807 | { |
Kirill A. Shutemov | b46e756 | 2016-07-26 15:26:24 -0700 | [diff] [blame] | 808 | VM_BUG_ON(!*hpage); |
| 809 | |
| 810 | return *hpage; |
| 811 | } |
| 812 | #endif |
| 813 | |
| 814 | static bool hugepage_vma_check(struct vm_area_struct *vma) |
| 815 | { |
| 816 | if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || |
| 817 | (vma->vm_flags & VM_NOHUGEPAGE)) |
| 818 | return false; |
| 819 | if (!vma->anon_vma || vma->vm_ops) |
| 820 | return false; |
| 821 | if (is_vma_temporary_stack(vma)) |
| 822 | return false; |
| 823 | return !(vma->vm_flags & VM_NO_KHUGEPAGED); |
| 824 | } |
| 825 | |
| 826 | /* |
| 827 | * If mmap_sem temporarily dropped, revalidate vma |
| 828 | * before taking mmap_sem. |
| 829 | * Return 0 if succeeds, otherwise return none-zero |
| 830 | * value (scan code). |
| 831 | */ |
| 832 | |
| 833 | static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address) |
| 834 | { |
| 835 | struct vm_area_struct *vma; |
| 836 | unsigned long hstart, hend; |
| 837 | |
| 838 | if (unlikely(khugepaged_test_exit(mm))) |
| 839 | return SCAN_ANY_PROCESS; |
| 840 | |
| 841 | vma = find_vma(mm, address); |
| 842 | if (!vma) |
| 843 | return SCAN_VMA_NULL; |
| 844 | |
| 845 | hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; |
| 846 | hend = vma->vm_end & HPAGE_PMD_MASK; |
| 847 | if (address < hstart || address + HPAGE_PMD_SIZE > hend) |
| 848 | return SCAN_ADDRESS_RANGE; |
| 849 | if (!hugepage_vma_check(vma)) |
| 850 | return SCAN_VMA_CHECK; |
| 851 | return 0; |
| 852 | } |
| 853 | |
| 854 | /* |
| 855 | * Bring missing pages in from swap, to complete THP collapse. |
| 856 | * Only done if khugepaged_scan_pmd believes it is worthwhile. |
| 857 | * |
| 858 | * Called and returns without pte mapped or spinlocks held, |
| 859 | * but with mmap_sem held to protect against vma changes. |
| 860 | */ |
| 861 | |
| 862 | static bool __collapse_huge_page_swapin(struct mm_struct *mm, |
| 863 | struct vm_area_struct *vma, |
| 864 | unsigned long address, pmd_t *pmd) |
| 865 | { |
| 866 | pte_t pteval; |
| 867 | int swapped_in = 0, ret = 0; |
| 868 | struct fault_env fe = { |
| 869 | .vma = vma, |
| 870 | .address = address, |
| 871 | .flags = FAULT_FLAG_ALLOW_RETRY, |
| 872 | .pmd = pmd, |
| 873 | }; |
| 874 | |
| 875 | fe.pte = pte_offset_map(pmd, address); |
| 876 | for (; fe.address < address + HPAGE_PMD_NR*PAGE_SIZE; |
| 877 | fe.pte++, fe.address += PAGE_SIZE) { |
| 878 | pteval = *fe.pte; |
| 879 | if (!is_swap_pte(pteval)) |
| 880 | continue; |
| 881 | swapped_in++; |
| 882 | ret = do_swap_page(&fe, pteval); |
| 883 | /* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */ |
| 884 | if (ret & VM_FAULT_RETRY) { |
| 885 | down_read(&mm->mmap_sem); |
| 886 | /* vma is no longer available, don't continue to swapin */ |
| 887 | if (hugepage_vma_revalidate(mm, address)) |
| 888 | return false; |
| 889 | /* check if the pmd is still valid */ |
| 890 | if (mm_find_pmd(mm, address) != pmd) |
| 891 | return false; |
| 892 | } |
| 893 | if (ret & VM_FAULT_ERROR) { |
| 894 | trace_mm_collapse_huge_page_swapin(mm, swapped_in, 0); |
| 895 | return false; |
| 896 | } |
| 897 | /* pte is unmapped now, we need to map it */ |
| 898 | fe.pte = pte_offset_map(pmd, fe.address); |
| 899 | } |
| 900 | fe.pte--; |
| 901 | pte_unmap(fe.pte); |
| 902 | trace_mm_collapse_huge_page_swapin(mm, swapped_in, 1); |
| 903 | return true; |
| 904 | } |
| 905 | |
| 906 | static void collapse_huge_page(struct mm_struct *mm, |
| 907 | unsigned long address, |
| 908 | struct page **hpage, |
| 909 | struct vm_area_struct *vma, |
| 910 | int node) |
| 911 | { |
| 912 | pmd_t *pmd, _pmd; |
| 913 | pte_t *pte; |
| 914 | pgtable_t pgtable; |
| 915 | struct page *new_page; |
| 916 | spinlock_t *pmd_ptl, *pte_ptl; |
| 917 | int isolated = 0, result = 0; |
| 918 | struct mem_cgroup *memcg; |
| 919 | unsigned long mmun_start; /* For mmu_notifiers */ |
| 920 | unsigned long mmun_end; /* For mmu_notifiers */ |
| 921 | gfp_t gfp; |
| 922 | |
| 923 | VM_BUG_ON(address & ~HPAGE_PMD_MASK); |
| 924 | |
| 925 | /* Only allocate from the target node */ |
| 926 | gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_OTHER_NODE | __GFP_THISNODE; |
| 927 | |
Kirill A. Shutemov | 988ddb7 | 2016-07-26 15:26:26 -0700 | [diff] [blame^] | 928 | /* |
| 929 | * Before allocating the hugepage, release the mmap_sem read lock. |
| 930 | * The allocation can take potentially a long time if it involves |
| 931 | * sync compaction, and we do not need to hold the mmap_sem during |
| 932 | * that. We will recheck the vma after taking it again in write mode. |
| 933 | */ |
| 934 | up_read(&mm->mmap_sem); |
| 935 | new_page = khugepaged_alloc_page(hpage, gfp, node); |
Kirill A. Shutemov | b46e756 | 2016-07-26 15:26:24 -0700 | [diff] [blame] | 936 | if (!new_page) { |
| 937 | result = SCAN_ALLOC_HUGE_PAGE_FAIL; |
| 938 | goto out_nolock; |
| 939 | } |
| 940 | |
| 941 | if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) { |
| 942 | result = SCAN_CGROUP_CHARGE_FAIL; |
| 943 | goto out_nolock; |
| 944 | } |
| 945 | |
| 946 | down_read(&mm->mmap_sem); |
| 947 | result = hugepage_vma_revalidate(mm, address); |
| 948 | if (result) { |
| 949 | mem_cgroup_cancel_charge(new_page, memcg, true); |
| 950 | up_read(&mm->mmap_sem); |
| 951 | goto out_nolock; |
| 952 | } |
| 953 | |
| 954 | pmd = mm_find_pmd(mm, address); |
| 955 | if (!pmd) { |
| 956 | result = SCAN_PMD_NULL; |
| 957 | mem_cgroup_cancel_charge(new_page, memcg, true); |
| 958 | up_read(&mm->mmap_sem); |
| 959 | goto out_nolock; |
| 960 | } |
| 961 | |
| 962 | /* |
| 963 | * __collapse_huge_page_swapin always returns with mmap_sem locked. |
| 964 | * If it fails, release mmap_sem and jump directly out. |
| 965 | * Continuing to collapse causes inconsistency. |
| 966 | */ |
| 967 | if (!__collapse_huge_page_swapin(mm, vma, address, pmd)) { |
| 968 | mem_cgroup_cancel_charge(new_page, memcg, true); |
| 969 | up_read(&mm->mmap_sem); |
| 970 | goto out_nolock; |
| 971 | } |
| 972 | |
| 973 | up_read(&mm->mmap_sem); |
| 974 | /* |
| 975 | * Prevent all access to pagetables with the exception of |
| 976 | * gup_fast later handled by the ptep_clear_flush and the VM |
| 977 | * handled by the anon_vma lock + PG_lock. |
| 978 | */ |
| 979 | down_write(&mm->mmap_sem); |
| 980 | result = hugepage_vma_revalidate(mm, address); |
| 981 | if (result) |
| 982 | goto out; |
| 983 | /* check if the pmd is still valid */ |
| 984 | if (mm_find_pmd(mm, address) != pmd) |
| 985 | goto out; |
| 986 | |
| 987 | anon_vma_lock_write(vma->anon_vma); |
| 988 | |
| 989 | pte = pte_offset_map(pmd, address); |
| 990 | pte_ptl = pte_lockptr(mm, pmd); |
| 991 | |
| 992 | mmun_start = address; |
| 993 | mmun_end = address + HPAGE_PMD_SIZE; |
| 994 | mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); |
| 995 | pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */ |
| 996 | /* |
| 997 | * After this gup_fast can't run anymore. This also removes |
| 998 | * any huge TLB entry from the CPU so we won't allow |
| 999 | * huge and small TLB entries for the same virtual address |
| 1000 | * to avoid the risk of CPU bugs in that area. |
| 1001 | */ |
| 1002 | _pmd = pmdp_collapse_flush(vma, address, pmd); |
| 1003 | spin_unlock(pmd_ptl); |
| 1004 | mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); |
| 1005 | |
| 1006 | spin_lock(pte_ptl); |
| 1007 | isolated = __collapse_huge_page_isolate(vma, address, pte); |
| 1008 | spin_unlock(pte_ptl); |
| 1009 | |
| 1010 | if (unlikely(!isolated)) { |
| 1011 | pte_unmap(pte); |
| 1012 | spin_lock(pmd_ptl); |
| 1013 | BUG_ON(!pmd_none(*pmd)); |
| 1014 | /* |
| 1015 | * We can only use set_pmd_at when establishing |
| 1016 | * hugepmds and never for establishing regular pmds that |
| 1017 | * points to regular pagetables. Use pmd_populate for that |
| 1018 | */ |
| 1019 | pmd_populate(mm, pmd, pmd_pgtable(_pmd)); |
| 1020 | spin_unlock(pmd_ptl); |
| 1021 | anon_vma_unlock_write(vma->anon_vma); |
| 1022 | result = SCAN_FAIL; |
| 1023 | goto out; |
| 1024 | } |
| 1025 | |
| 1026 | /* |
| 1027 | * All pages are isolated and locked so anon_vma rmap |
| 1028 | * can't run anymore. |
| 1029 | */ |
| 1030 | anon_vma_unlock_write(vma->anon_vma); |
| 1031 | |
| 1032 | __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl); |
| 1033 | pte_unmap(pte); |
| 1034 | __SetPageUptodate(new_page); |
| 1035 | pgtable = pmd_pgtable(_pmd); |
| 1036 | |
| 1037 | _pmd = mk_huge_pmd(new_page, vma->vm_page_prot); |
| 1038 | _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); |
| 1039 | |
| 1040 | /* |
| 1041 | * spin_lock() below is not the equivalent of smp_wmb(), so |
| 1042 | * this is needed to avoid the copy_huge_page writes to become |
| 1043 | * visible after the set_pmd_at() write. |
| 1044 | */ |
| 1045 | smp_wmb(); |
| 1046 | |
| 1047 | spin_lock(pmd_ptl); |
| 1048 | BUG_ON(!pmd_none(*pmd)); |
| 1049 | page_add_new_anon_rmap(new_page, vma, address, true); |
| 1050 | mem_cgroup_commit_charge(new_page, memcg, false, true); |
| 1051 | lru_cache_add_active_or_unevictable(new_page, vma); |
| 1052 | pgtable_trans_huge_deposit(mm, pmd, pgtable); |
| 1053 | set_pmd_at(mm, address, pmd, _pmd); |
| 1054 | update_mmu_cache_pmd(vma, address, pmd); |
| 1055 | spin_unlock(pmd_ptl); |
| 1056 | |
| 1057 | *hpage = NULL; |
| 1058 | |
| 1059 | khugepaged_pages_collapsed++; |
| 1060 | result = SCAN_SUCCEED; |
| 1061 | out_up_write: |
| 1062 | up_write(&mm->mmap_sem); |
| 1063 | out_nolock: |
| 1064 | trace_mm_collapse_huge_page(mm, isolated, result); |
| 1065 | return; |
| 1066 | out: |
| 1067 | mem_cgroup_cancel_charge(new_page, memcg, true); |
| 1068 | goto out_up_write; |
| 1069 | } |
| 1070 | |
| 1071 | static int khugepaged_scan_pmd(struct mm_struct *mm, |
| 1072 | struct vm_area_struct *vma, |
| 1073 | unsigned long address, |
| 1074 | struct page **hpage) |
| 1075 | { |
| 1076 | pmd_t *pmd; |
| 1077 | pte_t *pte, *_pte; |
| 1078 | int ret = 0, none_or_zero = 0, result = 0; |
| 1079 | struct page *page = NULL; |
| 1080 | unsigned long _address; |
| 1081 | spinlock_t *ptl; |
| 1082 | int node = NUMA_NO_NODE, unmapped = 0; |
| 1083 | bool writable = false, referenced = false; |
| 1084 | |
| 1085 | VM_BUG_ON(address & ~HPAGE_PMD_MASK); |
| 1086 | |
| 1087 | pmd = mm_find_pmd(mm, address); |
| 1088 | if (!pmd) { |
| 1089 | result = SCAN_PMD_NULL; |
| 1090 | goto out; |
| 1091 | } |
| 1092 | |
| 1093 | memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); |
| 1094 | pte = pte_offset_map_lock(mm, pmd, address, &ptl); |
| 1095 | for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; |
| 1096 | _pte++, _address += PAGE_SIZE) { |
| 1097 | pte_t pteval = *_pte; |
| 1098 | if (is_swap_pte(pteval)) { |
| 1099 | if (++unmapped <= khugepaged_max_ptes_swap) { |
| 1100 | continue; |
| 1101 | } else { |
| 1102 | result = SCAN_EXCEED_SWAP_PTE; |
| 1103 | goto out_unmap; |
| 1104 | } |
| 1105 | } |
| 1106 | if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { |
| 1107 | if (!userfaultfd_armed(vma) && |
| 1108 | ++none_or_zero <= khugepaged_max_ptes_none) { |
| 1109 | continue; |
| 1110 | } else { |
| 1111 | result = SCAN_EXCEED_NONE_PTE; |
| 1112 | goto out_unmap; |
| 1113 | } |
| 1114 | } |
| 1115 | if (!pte_present(pteval)) { |
| 1116 | result = SCAN_PTE_NON_PRESENT; |
| 1117 | goto out_unmap; |
| 1118 | } |
| 1119 | if (pte_write(pteval)) |
| 1120 | writable = true; |
| 1121 | |
| 1122 | page = vm_normal_page(vma, _address, pteval); |
| 1123 | if (unlikely(!page)) { |
| 1124 | result = SCAN_PAGE_NULL; |
| 1125 | goto out_unmap; |
| 1126 | } |
| 1127 | |
| 1128 | /* TODO: teach khugepaged to collapse THP mapped with pte */ |
| 1129 | if (PageCompound(page)) { |
| 1130 | result = SCAN_PAGE_COMPOUND; |
| 1131 | goto out_unmap; |
| 1132 | } |
| 1133 | |
| 1134 | /* |
| 1135 | * Record which node the original page is from and save this |
| 1136 | * information to khugepaged_node_load[]. |
| 1137 | * Khupaged will allocate hugepage from the node has the max |
| 1138 | * hit record. |
| 1139 | */ |
| 1140 | node = page_to_nid(page); |
| 1141 | if (khugepaged_scan_abort(node)) { |
| 1142 | result = SCAN_SCAN_ABORT; |
| 1143 | goto out_unmap; |
| 1144 | } |
| 1145 | khugepaged_node_load[node]++; |
| 1146 | if (!PageLRU(page)) { |
| 1147 | result = SCAN_PAGE_LRU; |
| 1148 | goto out_unmap; |
| 1149 | } |
| 1150 | if (PageLocked(page)) { |
| 1151 | result = SCAN_PAGE_LOCK; |
| 1152 | goto out_unmap; |
| 1153 | } |
| 1154 | if (!PageAnon(page)) { |
| 1155 | result = SCAN_PAGE_ANON; |
| 1156 | goto out_unmap; |
| 1157 | } |
| 1158 | |
| 1159 | /* |
| 1160 | * cannot use mapcount: can't collapse if there's a gup pin. |
| 1161 | * The page must only be referenced by the scanned process |
| 1162 | * and page swap cache. |
| 1163 | */ |
| 1164 | if (page_count(page) != 1 + !!PageSwapCache(page)) { |
| 1165 | result = SCAN_PAGE_COUNT; |
| 1166 | goto out_unmap; |
| 1167 | } |
| 1168 | if (pte_young(pteval) || |
| 1169 | page_is_young(page) || PageReferenced(page) || |
| 1170 | mmu_notifier_test_young(vma->vm_mm, address)) |
| 1171 | referenced = true; |
| 1172 | } |
| 1173 | if (writable) { |
| 1174 | if (referenced) { |
| 1175 | result = SCAN_SUCCEED; |
| 1176 | ret = 1; |
| 1177 | } else { |
| 1178 | result = SCAN_NO_REFERENCED_PAGE; |
| 1179 | } |
| 1180 | } else { |
| 1181 | result = SCAN_PAGE_RO; |
| 1182 | } |
| 1183 | out_unmap: |
| 1184 | pte_unmap_unlock(pte, ptl); |
| 1185 | if (ret) { |
| 1186 | node = khugepaged_find_target_node(); |
| 1187 | /* collapse_huge_page will return with the mmap_sem released */ |
| 1188 | collapse_huge_page(mm, address, hpage, vma, node); |
| 1189 | } |
| 1190 | out: |
| 1191 | trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced, |
| 1192 | none_or_zero, result, unmapped); |
| 1193 | return ret; |
| 1194 | } |
| 1195 | |
| 1196 | static void collect_mm_slot(struct mm_slot *mm_slot) |
| 1197 | { |
| 1198 | struct mm_struct *mm = mm_slot->mm; |
| 1199 | |
| 1200 | VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); |
| 1201 | |
| 1202 | if (khugepaged_test_exit(mm)) { |
| 1203 | /* free mm_slot */ |
| 1204 | hash_del(&mm_slot->hash); |
| 1205 | list_del(&mm_slot->mm_node); |
| 1206 | |
| 1207 | /* |
| 1208 | * Not strictly needed because the mm exited already. |
| 1209 | * |
| 1210 | * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); |
| 1211 | */ |
| 1212 | |
| 1213 | /* khugepaged_mm_lock actually not necessary for the below */ |
| 1214 | free_mm_slot(mm_slot); |
| 1215 | mmdrop(mm); |
| 1216 | } |
| 1217 | } |
| 1218 | |
| 1219 | static unsigned int khugepaged_scan_mm_slot(unsigned int pages, |
| 1220 | struct page **hpage) |
| 1221 | __releases(&khugepaged_mm_lock) |
| 1222 | __acquires(&khugepaged_mm_lock) |
| 1223 | { |
| 1224 | struct mm_slot *mm_slot; |
| 1225 | struct mm_struct *mm; |
| 1226 | struct vm_area_struct *vma; |
| 1227 | int progress = 0; |
| 1228 | |
| 1229 | VM_BUG_ON(!pages); |
| 1230 | VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); |
| 1231 | |
| 1232 | if (khugepaged_scan.mm_slot) |
| 1233 | mm_slot = khugepaged_scan.mm_slot; |
| 1234 | else { |
| 1235 | mm_slot = list_entry(khugepaged_scan.mm_head.next, |
| 1236 | struct mm_slot, mm_node); |
| 1237 | khugepaged_scan.address = 0; |
| 1238 | khugepaged_scan.mm_slot = mm_slot; |
| 1239 | } |
| 1240 | spin_unlock(&khugepaged_mm_lock); |
| 1241 | |
| 1242 | mm = mm_slot->mm; |
| 1243 | down_read(&mm->mmap_sem); |
| 1244 | if (unlikely(khugepaged_test_exit(mm))) |
| 1245 | vma = NULL; |
| 1246 | else |
| 1247 | vma = find_vma(mm, khugepaged_scan.address); |
| 1248 | |
| 1249 | progress++; |
| 1250 | for (; vma; vma = vma->vm_next) { |
| 1251 | unsigned long hstart, hend; |
| 1252 | |
| 1253 | cond_resched(); |
| 1254 | if (unlikely(khugepaged_test_exit(mm))) { |
| 1255 | progress++; |
| 1256 | break; |
| 1257 | } |
| 1258 | if (!hugepage_vma_check(vma)) { |
| 1259 | skip: |
| 1260 | progress++; |
| 1261 | continue; |
| 1262 | } |
| 1263 | hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; |
| 1264 | hend = vma->vm_end & HPAGE_PMD_MASK; |
| 1265 | if (hstart >= hend) |
| 1266 | goto skip; |
| 1267 | if (khugepaged_scan.address > hend) |
| 1268 | goto skip; |
| 1269 | if (khugepaged_scan.address < hstart) |
| 1270 | khugepaged_scan.address = hstart; |
| 1271 | VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); |
| 1272 | |
| 1273 | while (khugepaged_scan.address < hend) { |
| 1274 | int ret; |
| 1275 | cond_resched(); |
| 1276 | if (unlikely(khugepaged_test_exit(mm))) |
| 1277 | goto breakouterloop; |
| 1278 | |
| 1279 | VM_BUG_ON(khugepaged_scan.address < hstart || |
| 1280 | khugepaged_scan.address + HPAGE_PMD_SIZE > |
| 1281 | hend); |
| 1282 | ret = khugepaged_scan_pmd(mm, vma, |
| 1283 | khugepaged_scan.address, |
| 1284 | hpage); |
| 1285 | /* move to next address */ |
| 1286 | khugepaged_scan.address += HPAGE_PMD_SIZE; |
| 1287 | progress += HPAGE_PMD_NR; |
| 1288 | if (ret) |
| 1289 | /* we released mmap_sem so break loop */ |
| 1290 | goto breakouterloop_mmap_sem; |
| 1291 | if (progress >= pages) |
| 1292 | goto breakouterloop; |
| 1293 | } |
| 1294 | } |
| 1295 | breakouterloop: |
| 1296 | up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */ |
| 1297 | breakouterloop_mmap_sem: |
| 1298 | |
| 1299 | spin_lock(&khugepaged_mm_lock); |
| 1300 | VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); |
| 1301 | /* |
| 1302 | * Release the current mm_slot if this mm is about to die, or |
| 1303 | * if we scanned all vmas of this mm. |
| 1304 | */ |
| 1305 | if (khugepaged_test_exit(mm) || !vma) { |
| 1306 | /* |
| 1307 | * Make sure that if mm_users is reaching zero while |
| 1308 | * khugepaged runs here, khugepaged_exit will find |
| 1309 | * mm_slot not pointing to the exiting mm. |
| 1310 | */ |
| 1311 | if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { |
| 1312 | khugepaged_scan.mm_slot = list_entry( |
| 1313 | mm_slot->mm_node.next, |
| 1314 | struct mm_slot, mm_node); |
| 1315 | khugepaged_scan.address = 0; |
| 1316 | } else { |
| 1317 | khugepaged_scan.mm_slot = NULL; |
| 1318 | khugepaged_full_scans++; |
| 1319 | } |
| 1320 | |
| 1321 | collect_mm_slot(mm_slot); |
| 1322 | } |
| 1323 | |
| 1324 | return progress; |
| 1325 | } |
| 1326 | |
| 1327 | static int khugepaged_has_work(void) |
| 1328 | { |
| 1329 | return !list_empty(&khugepaged_scan.mm_head) && |
| 1330 | khugepaged_enabled(); |
| 1331 | } |
| 1332 | |
| 1333 | static int khugepaged_wait_event(void) |
| 1334 | { |
| 1335 | return !list_empty(&khugepaged_scan.mm_head) || |
| 1336 | kthread_should_stop(); |
| 1337 | } |
| 1338 | |
| 1339 | static void khugepaged_do_scan(void) |
| 1340 | { |
| 1341 | struct page *hpage = NULL; |
| 1342 | unsigned int progress = 0, pass_through_head = 0; |
| 1343 | unsigned int pages = khugepaged_pages_to_scan; |
| 1344 | bool wait = true; |
| 1345 | |
| 1346 | barrier(); /* write khugepaged_pages_to_scan to local stack */ |
| 1347 | |
| 1348 | while (progress < pages) { |
| 1349 | if (!khugepaged_prealloc_page(&hpage, &wait)) |
| 1350 | break; |
| 1351 | |
| 1352 | cond_resched(); |
| 1353 | |
| 1354 | if (unlikely(kthread_should_stop() || try_to_freeze())) |
| 1355 | break; |
| 1356 | |
| 1357 | spin_lock(&khugepaged_mm_lock); |
| 1358 | if (!khugepaged_scan.mm_slot) |
| 1359 | pass_through_head++; |
| 1360 | if (khugepaged_has_work() && |
| 1361 | pass_through_head < 2) |
| 1362 | progress += khugepaged_scan_mm_slot(pages - progress, |
| 1363 | &hpage); |
| 1364 | else |
| 1365 | progress = pages; |
| 1366 | spin_unlock(&khugepaged_mm_lock); |
| 1367 | } |
| 1368 | |
| 1369 | if (!IS_ERR_OR_NULL(hpage)) |
| 1370 | put_page(hpage); |
| 1371 | } |
| 1372 | |
| 1373 | static bool khugepaged_should_wakeup(void) |
| 1374 | { |
| 1375 | return kthread_should_stop() || |
| 1376 | time_after_eq(jiffies, khugepaged_sleep_expire); |
| 1377 | } |
| 1378 | |
| 1379 | static void khugepaged_wait_work(void) |
| 1380 | { |
| 1381 | if (khugepaged_has_work()) { |
| 1382 | const unsigned long scan_sleep_jiffies = |
| 1383 | msecs_to_jiffies(khugepaged_scan_sleep_millisecs); |
| 1384 | |
| 1385 | if (!scan_sleep_jiffies) |
| 1386 | return; |
| 1387 | |
| 1388 | khugepaged_sleep_expire = jiffies + scan_sleep_jiffies; |
| 1389 | wait_event_freezable_timeout(khugepaged_wait, |
| 1390 | khugepaged_should_wakeup(), |
| 1391 | scan_sleep_jiffies); |
| 1392 | return; |
| 1393 | } |
| 1394 | |
| 1395 | if (khugepaged_enabled()) |
| 1396 | wait_event_freezable(khugepaged_wait, khugepaged_wait_event()); |
| 1397 | } |
| 1398 | |
| 1399 | static int khugepaged(void *none) |
| 1400 | { |
| 1401 | struct mm_slot *mm_slot; |
| 1402 | |
| 1403 | set_freezable(); |
| 1404 | set_user_nice(current, MAX_NICE); |
| 1405 | |
| 1406 | while (!kthread_should_stop()) { |
| 1407 | khugepaged_do_scan(); |
| 1408 | khugepaged_wait_work(); |
| 1409 | } |
| 1410 | |
| 1411 | spin_lock(&khugepaged_mm_lock); |
| 1412 | mm_slot = khugepaged_scan.mm_slot; |
| 1413 | khugepaged_scan.mm_slot = NULL; |
| 1414 | if (mm_slot) |
| 1415 | collect_mm_slot(mm_slot); |
| 1416 | spin_unlock(&khugepaged_mm_lock); |
| 1417 | return 0; |
| 1418 | } |
| 1419 | |
| 1420 | static void set_recommended_min_free_kbytes(void) |
| 1421 | { |
| 1422 | struct zone *zone; |
| 1423 | int nr_zones = 0; |
| 1424 | unsigned long recommended_min; |
| 1425 | |
| 1426 | for_each_populated_zone(zone) |
| 1427 | nr_zones++; |
| 1428 | |
| 1429 | /* Ensure 2 pageblocks are free to assist fragmentation avoidance */ |
| 1430 | recommended_min = pageblock_nr_pages * nr_zones * 2; |
| 1431 | |
| 1432 | /* |
| 1433 | * Make sure that on average at least two pageblocks are almost free |
| 1434 | * of another type, one for a migratetype to fall back to and a |
| 1435 | * second to avoid subsequent fallbacks of other types There are 3 |
| 1436 | * MIGRATE_TYPES we care about. |
| 1437 | */ |
| 1438 | recommended_min += pageblock_nr_pages * nr_zones * |
| 1439 | MIGRATE_PCPTYPES * MIGRATE_PCPTYPES; |
| 1440 | |
| 1441 | /* don't ever allow to reserve more than 5% of the lowmem */ |
| 1442 | recommended_min = min(recommended_min, |
| 1443 | (unsigned long) nr_free_buffer_pages() / 20); |
| 1444 | recommended_min <<= (PAGE_SHIFT-10); |
| 1445 | |
| 1446 | if (recommended_min > min_free_kbytes) { |
| 1447 | if (user_min_free_kbytes >= 0) |
| 1448 | pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n", |
| 1449 | min_free_kbytes, recommended_min); |
| 1450 | |
| 1451 | min_free_kbytes = recommended_min; |
| 1452 | } |
| 1453 | setup_per_zone_wmarks(); |
| 1454 | } |
| 1455 | |
| 1456 | int start_stop_khugepaged(void) |
| 1457 | { |
| 1458 | static struct task_struct *khugepaged_thread __read_mostly; |
| 1459 | static DEFINE_MUTEX(khugepaged_mutex); |
| 1460 | int err = 0; |
| 1461 | |
| 1462 | mutex_lock(&khugepaged_mutex); |
| 1463 | if (khugepaged_enabled()) { |
| 1464 | if (!khugepaged_thread) |
| 1465 | khugepaged_thread = kthread_run(khugepaged, NULL, |
| 1466 | "khugepaged"); |
| 1467 | if (IS_ERR(khugepaged_thread)) { |
| 1468 | pr_err("khugepaged: kthread_run(khugepaged) failed\n"); |
| 1469 | err = PTR_ERR(khugepaged_thread); |
| 1470 | khugepaged_thread = NULL; |
| 1471 | goto fail; |
| 1472 | } |
| 1473 | |
| 1474 | if (!list_empty(&khugepaged_scan.mm_head)) |
| 1475 | wake_up_interruptible(&khugepaged_wait); |
| 1476 | |
| 1477 | set_recommended_min_free_kbytes(); |
| 1478 | } else if (khugepaged_thread) { |
| 1479 | kthread_stop(khugepaged_thread); |
| 1480 | khugepaged_thread = NULL; |
| 1481 | } |
| 1482 | fail: |
| 1483 | mutex_unlock(&khugepaged_mutex); |
| 1484 | return err; |
| 1485 | } |