1 // SPDX-License-Identifier: GPL-2.0
2 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
5 #include <linux/sched.h>
6 #include <linux/sched/mm.h>
7 #include <linux/sched/coredump.h>
8 #include <linux/mmu_notifier.h>
9 #include <linux/rmap.h>
10 #include <linux/swap.h>
11 #include <linux/mm_inline.h>
12 #include <linux/kthread.h>
13 #include <linux/khugepaged.h>
14 #include <linux/freezer.h>
15 #include <linux/mman.h>
16 #include <linux/hashtable.h>
17 #include <linux/userfaultfd_k.h>
18 #include <linux/page_idle.h>
19 #include <linux/swapops.h>
20 #include <linux/shmem_fs.h>
23 #include <asm/pgalloc.h>
32 SCAN_EXCEED_SHARED_PTE
,
36 SCAN_LACK_REFERENCED_PAGE
,
50 SCAN_ALLOC_HUGE_PAGE_FAIL
,
51 SCAN_CGROUP_CHARGE_FAIL
,
53 SCAN_PAGE_HAS_PRIVATE
,
56 #define CREATE_TRACE_POINTS
57 #include <trace/events/huge_memory.h>
59 static struct task_struct
*khugepaged_thread __read_mostly
;
60 static DEFINE_MUTEX(khugepaged_mutex
);
62 /* default scan 8*512 pte (or vmas) every 30 second */
63 static unsigned int khugepaged_pages_to_scan __read_mostly
;
64 static unsigned int khugepaged_pages_collapsed
;
65 static unsigned int khugepaged_full_scans
;
66 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly
= 10000;
67 /* during fragmentation poll the hugepage allocator once every minute */
68 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly
= 60000;
69 static unsigned long khugepaged_sleep_expire
;
70 static DEFINE_SPINLOCK(khugepaged_mm_lock
);
71 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait
);
73 * default collapse hugepages if there is at least one pte mapped like
74 * it would have happened if the vma was large enough during page
77 static unsigned int khugepaged_max_ptes_none __read_mostly
;
78 static unsigned int khugepaged_max_ptes_swap __read_mostly
;
79 static unsigned int khugepaged_max_ptes_shared __read_mostly
;
81 #define MM_SLOTS_HASH_BITS 10
82 static __read_mostly
DEFINE_HASHTABLE(mm_slots_hash
, MM_SLOTS_HASH_BITS
);
84 static struct kmem_cache
*mm_slot_cache __read_mostly
;
86 #define MAX_PTE_MAPPED_THP 8
89 * struct mm_slot - hash lookup from mm to mm_slot
90 * @hash: hash collision list
91 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
92 * @mm: the mm that this information is valid for
95 struct hlist_node hash
;
96 struct list_head mm_node
;
99 /* pte-mapped THP in this mm */
100 int nr_pte_mapped_thp
;
101 unsigned long pte_mapped_thp
[MAX_PTE_MAPPED_THP
];
105 * struct khugepaged_scan - cursor for scanning
106 * @mm_head: the head of the mm list to scan
107 * @mm_slot: the current mm_slot we are scanning
108 * @address: the next address inside that to be scanned
110 * There is only the one khugepaged_scan instance of this cursor structure.
112 struct khugepaged_scan
{
113 struct list_head mm_head
;
114 struct mm_slot
*mm_slot
;
115 unsigned long address
;
118 static struct khugepaged_scan khugepaged_scan
= {
119 .mm_head
= LIST_HEAD_INIT(khugepaged_scan
.mm_head
),
123 static ssize_t
scan_sleep_millisecs_show(struct kobject
*kobj
,
124 struct kobj_attribute
*attr
,
127 return sprintf(buf
, "%u\n", khugepaged_scan_sleep_millisecs
);
130 static ssize_t
scan_sleep_millisecs_store(struct kobject
*kobj
,
131 struct kobj_attribute
*attr
,
132 const char *buf
, size_t count
)
137 err
= kstrtoul(buf
, 10, &msecs
);
138 if (err
|| msecs
> UINT_MAX
)
141 khugepaged_scan_sleep_millisecs
= msecs
;
142 khugepaged_sleep_expire
= 0;
143 wake_up_interruptible(&khugepaged_wait
);
147 static struct kobj_attribute scan_sleep_millisecs_attr
=
148 __ATTR(scan_sleep_millisecs
, 0644, scan_sleep_millisecs_show
,
149 scan_sleep_millisecs_store
);
151 static ssize_t
alloc_sleep_millisecs_show(struct kobject
*kobj
,
152 struct kobj_attribute
*attr
,
155 return sprintf(buf
, "%u\n", khugepaged_alloc_sleep_millisecs
);
158 static ssize_t
alloc_sleep_millisecs_store(struct kobject
*kobj
,
159 struct kobj_attribute
*attr
,
160 const char *buf
, size_t count
)
165 err
= kstrtoul(buf
, 10, &msecs
);
166 if (err
|| msecs
> UINT_MAX
)
169 khugepaged_alloc_sleep_millisecs
= msecs
;
170 khugepaged_sleep_expire
= 0;
171 wake_up_interruptible(&khugepaged_wait
);
175 static struct kobj_attribute alloc_sleep_millisecs_attr
=
176 __ATTR(alloc_sleep_millisecs
, 0644, alloc_sleep_millisecs_show
,
177 alloc_sleep_millisecs_store
);
179 static ssize_t
pages_to_scan_show(struct kobject
*kobj
,
180 struct kobj_attribute
*attr
,
183 return sprintf(buf
, "%u\n", khugepaged_pages_to_scan
);
185 static ssize_t
pages_to_scan_store(struct kobject
*kobj
,
186 struct kobj_attribute
*attr
,
187 const char *buf
, size_t count
)
192 err
= kstrtoul(buf
, 10, &pages
);
193 if (err
|| !pages
|| pages
> UINT_MAX
)
196 khugepaged_pages_to_scan
= pages
;
200 static struct kobj_attribute pages_to_scan_attr
=
201 __ATTR(pages_to_scan
, 0644, pages_to_scan_show
,
202 pages_to_scan_store
);
204 static ssize_t
pages_collapsed_show(struct kobject
*kobj
,
205 struct kobj_attribute
*attr
,
208 return sprintf(buf
, "%u\n", khugepaged_pages_collapsed
);
210 static struct kobj_attribute pages_collapsed_attr
=
211 __ATTR_RO(pages_collapsed
);
213 static ssize_t
full_scans_show(struct kobject
*kobj
,
214 struct kobj_attribute
*attr
,
217 return sprintf(buf
, "%u\n", khugepaged_full_scans
);
219 static struct kobj_attribute full_scans_attr
=
220 __ATTR_RO(full_scans
);
222 static ssize_t
khugepaged_defrag_show(struct kobject
*kobj
,
223 struct kobj_attribute
*attr
, char *buf
)
225 return single_hugepage_flag_show(kobj
, attr
, buf
,
226 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG
);
228 static ssize_t
khugepaged_defrag_store(struct kobject
*kobj
,
229 struct kobj_attribute
*attr
,
230 const char *buf
, size_t count
)
232 return single_hugepage_flag_store(kobj
, attr
, buf
, count
,
233 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG
);
235 static struct kobj_attribute khugepaged_defrag_attr
=
236 __ATTR(defrag
, 0644, khugepaged_defrag_show
,
237 khugepaged_defrag_store
);
240 * max_ptes_none controls if khugepaged should collapse hugepages over
241 * any unmapped ptes in turn potentially increasing the memory
242 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
243 * reduce the available free memory in the system as it
244 * runs. Increasing max_ptes_none will instead potentially reduce the
245 * free memory in the system during the khugepaged scan.
247 static ssize_t
khugepaged_max_ptes_none_show(struct kobject
*kobj
,
248 struct kobj_attribute
*attr
,
251 return sprintf(buf
, "%u\n", khugepaged_max_ptes_none
);
253 static ssize_t
khugepaged_max_ptes_none_store(struct kobject
*kobj
,
254 struct kobj_attribute
*attr
,
255 const char *buf
, size_t count
)
258 unsigned long max_ptes_none
;
260 err
= kstrtoul(buf
, 10, &max_ptes_none
);
261 if (err
|| max_ptes_none
> HPAGE_PMD_NR
-1)
264 khugepaged_max_ptes_none
= max_ptes_none
;
268 static struct kobj_attribute khugepaged_max_ptes_none_attr
=
269 __ATTR(max_ptes_none
, 0644, khugepaged_max_ptes_none_show
,
270 khugepaged_max_ptes_none_store
);
272 static ssize_t
khugepaged_max_ptes_swap_show(struct kobject
*kobj
,
273 struct kobj_attribute
*attr
,
276 return sprintf(buf
, "%u\n", khugepaged_max_ptes_swap
);
279 static ssize_t
khugepaged_max_ptes_swap_store(struct kobject
*kobj
,
280 struct kobj_attribute
*attr
,
281 const char *buf
, size_t count
)
284 unsigned long max_ptes_swap
;
286 err
= kstrtoul(buf
, 10, &max_ptes_swap
);
287 if (err
|| max_ptes_swap
> HPAGE_PMD_NR
-1)
290 khugepaged_max_ptes_swap
= max_ptes_swap
;
295 static struct kobj_attribute khugepaged_max_ptes_swap_attr
=
296 __ATTR(max_ptes_swap
, 0644, khugepaged_max_ptes_swap_show
,
297 khugepaged_max_ptes_swap_store
);
299 static ssize_t
khugepaged_max_ptes_shared_show(struct kobject
*kobj
,
300 struct kobj_attribute
*attr
,
303 return sprintf(buf
, "%u\n", khugepaged_max_ptes_shared
);
306 static ssize_t
khugepaged_max_ptes_shared_store(struct kobject
*kobj
,
307 struct kobj_attribute
*attr
,
308 const char *buf
, size_t count
)
311 unsigned long max_ptes_shared
;
313 err
= kstrtoul(buf
, 10, &max_ptes_shared
);
314 if (err
|| max_ptes_shared
> HPAGE_PMD_NR
-1)
317 khugepaged_max_ptes_shared
= max_ptes_shared
;
322 static struct kobj_attribute khugepaged_max_ptes_shared_attr
=
323 __ATTR(max_ptes_shared
, 0644, khugepaged_max_ptes_shared_show
,
324 khugepaged_max_ptes_shared_store
);
326 static struct attribute
*khugepaged_attr
[] = {
327 &khugepaged_defrag_attr
.attr
,
328 &khugepaged_max_ptes_none_attr
.attr
,
329 &khugepaged_max_ptes_swap_attr
.attr
,
330 &khugepaged_max_ptes_shared_attr
.attr
,
331 &pages_to_scan_attr
.attr
,
332 &pages_collapsed_attr
.attr
,
333 &full_scans_attr
.attr
,
334 &scan_sleep_millisecs_attr
.attr
,
335 &alloc_sleep_millisecs_attr
.attr
,
339 struct attribute_group khugepaged_attr_group
= {
340 .attrs
= khugepaged_attr
,
341 .name
= "khugepaged",
343 #endif /* CONFIG_SYSFS */
345 int hugepage_madvise(struct vm_area_struct
*vma
,
346 unsigned long *vm_flags
, int advice
)
352 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
353 * can't handle this properly after s390_enable_sie, so we simply
354 * ignore the madvise to prevent qemu from causing a SIGSEGV.
356 if (mm_has_pgste(vma
->vm_mm
))
359 *vm_flags
&= ~VM_NOHUGEPAGE
;
360 *vm_flags
|= VM_HUGEPAGE
;
362 * If the vma become good for khugepaged to scan,
363 * register it here without waiting a page fault that
364 * may not happen any time soon.
366 if (!(*vm_flags
& VM_NO_KHUGEPAGED
) &&
367 khugepaged_enter_vma_merge(vma
, *vm_flags
))
370 case MADV_NOHUGEPAGE
:
371 *vm_flags
&= ~VM_HUGEPAGE
;
372 *vm_flags
|= VM_NOHUGEPAGE
;
374 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
375 * this vma even if we leave the mm registered in khugepaged if
376 * it got registered before VM_NOHUGEPAGE was set.
384 int __init
khugepaged_init(void)
386 mm_slot_cache
= kmem_cache_create("khugepaged_mm_slot",
387 sizeof(struct mm_slot
),
388 __alignof__(struct mm_slot
), 0, NULL
);
392 khugepaged_pages_to_scan
= HPAGE_PMD_NR
* 8;
393 khugepaged_max_ptes_none
= HPAGE_PMD_NR
- 1;
394 khugepaged_max_ptes_swap
= HPAGE_PMD_NR
/ 8;
395 khugepaged_max_ptes_shared
= HPAGE_PMD_NR
/ 2;
400 void __init
khugepaged_destroy(void)
402 kmem_cache_destroy(mm_slot_cache
);
405 static inline struct mm_slot
*alloc_mm_slot(void)
407 if (!mm_slot_cache
) /* initialization failed */
409 return kmem_cache_zalloc(mm_slot_cache
, GFP_KERNEL
);
412 static inline void free_mm_slot(struct mm_slot
*mm_slot
)
414 kmem_cache_free(mm_slot_cache
, mm_slot
);
417 static struct mm_slot
*get_mm_slot(struct mm_struct
*mm
)
419 struct mm_slot
*mm_slot
;
421 hash_for_each_possible(mm_slots_hash
, mm_slot
, hash
, (unsigned long)mm
)
422 if (mm
== mm_slot
->mm
)
428 static void insert_to_mm_slots_hash(struct mm_struct
*mm
,
429 struct mm_slot
*mm_slot
)
432 hash_add(mm_slots_hash
, &mm_slot
->hash
, (long)mm
);
435 static inline int khugepaged_test_exit(struct mm_struct
*mm
)
437 return atomic_read(&mm
->mm_users
) == 0;
440 static bool hugepage_vma_check(struct vm_area_struct
*vma
,
441 unsigned long vm_flags
)
443 if ((!(vm_flags
& VM_HUGEPAGE
) && !khugepaged_always()) ||
444 (vm_flags
& VM_NOHUGEPAGE
) ||
445 test_bit(MMF_DISABLE_THP
, &vma
->vm_mm
->flags
))
448 if (shmem_file(vma
->vm_file
) ||
449 (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS
) &&
451 (vm_flags
& VM_DENYWRITE
))) {
452 return IS_ALIGNED((vma
->vm_start
>> PAGE_SHIFT
) - vma
->vm_pgoff
,
455 if (!vma
->anon_vma
|| vma
->vm_ops
)
457 if (vma_is_temporary_stack(vma
))
459 return !(vm_flags
& VM_NO_KHUGEPAGED
);
462 int __khugepaged_enter(struct mm_struct
*mm
)
464 struct mm_slot
*mm_slot
;
467 mm_slot
= alloc_mm_slot();
471 /* __khugepaged_exit() must not run from under us */
472 VM_BUG_ON_MM(atomic_read(&mm
->mm_users
) == 0, mm
);
473 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE
, &mm
->flags
))) {
474 free_mm_slot(mm_slot
);
478 spin_lock(&khugepaged_mm_lock
);
479 insert_to_mm_slots_hash(mm
, mm_slot
);
481 * Insert just behind the scanning cursor, to let the area settle
484 wakeup
= list_empty(&khugepaged_scan
.mm_head
);
485 list_add_tail(&mm_slot
->mm_node
, &khugepaged_scan
.mm_head
);
486 spin_unlock(&khugepaged_mm_lock
);
490 wake_up_interruptible(&khugepaged_wait
);
495 int khugepaged_enter_vma_merge(struct vm_area_struct
*vma
,
496 unsigned long vm_flags
)
498 unsigned long hstart
, hend
;
501 * khugepaged only supports read-only files for non-shmem files.
502 * khugepaged does not yet work on special mappings. And
503 * file-private shmem THP is not supported.
505 if (!hugepage_vma_check(vma
, vm_flags
))
508 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
509 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
511 return khugepaged_enter(vma
, vm_flags
);
515 void __khugepaged_exit(struct mm_struct
*mm
)
517 struct mm_slot
*mm_slot
;
520 spin_lock(&khugepaged_mm_lock
);
521 mm_slot
= get_mm_slot(mm
);
522 if (mm_slot
&& khugepaged_scan
.mm_slot
!= mm_slot
) {
523 hash_del(&mm_slot
->hash
);
524 list_del(&mm_slot
->mm_node
);
527 spin_unlock(&khugepaged_mm_lock
);
530 clear_bit(MMF_VM_HUGEPAGE
, &mm
->flags
);
531 free_mm_slot(mm_slot
);
533 } else if (mm_slot
) {
535 * This is required to serialize against
536 * khugepaged_test_exit() (which is guaranteed to run
537 * under mmap sem read mode). Stop here (after we
538 * return all pagetables will be destroyed) until
539 * khugepaged has finished working on the pagetables
540 * under the mmap_lock.
543 mmap_write_unlock(mm
);
547 static void release_pte_page(struct page
*page
)
549 mod_node_page_state(page_pgdat(page
),
550 NR_ISOLATED_ANON
+ page_is_file_lru(page
),
553 putback_lru_page(page
);
556 static void release_pte_pages(pte_t
*pte
, pte_t
*_pte
,
557 struct list_head
*compound_pagelist
)
559 struct page
*page
, *tmp
;
561 while (--_pte
>= pte
) {
562 pte_t pteval
= *_pte
;
564 page
= pte_page(pteval
);
565 if (!pte_none(pteval
) && !is_zero_pfn(pte_pfn(pteval
)) &&
567 release_pte_page(page
);
570 list_for_each_entry_safe(page
, tmp
, compound_pagelist
, lru
) {
571 list_del(&page
->lru
);
572 release_pte_page(page
);
576 static bool is_refcount_suitable(struct page
*page
)
578 int expected_refcount
;
580 expected_refcount
= total_mapcount(page
);
581 if (PageSwapCache(page
))
582 expected_refcount
+= compound_nr(page
);
584 return page_count(page
) == expected_refcount
;
587 static int __collapse_huge_page_isolate(struct vm_area_struct
*vma
,
588 unsigned long address
,
590 struct list_head
*compound_pagelist
)
592 struct page
*page
= NULL
;
594 int none_or_zero
= 0, shared
= 0, result
= 0, referenced
= 0;
595 bool writable
= false;
597 for (_pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
;
598 _pte
++, address
+= PAGE_SIZE
) {
599 pte_t pteval
= *_pte
;
600 if (pte_none(pteval
) || (pte_present(pteval
) &&
601 is_zero_pfn(pte_pfn(pteval
)))) {
602 if (!userfaultfd_armed(vma
) &&
603 ++none_or_zero
<= khugepaged_max_ptes_none
) {
606 result
= SCAN_EXCEED_NONE_PTE
;
610 if (!pte_present(pteval
)) {
611 result
= SCAN_PTE_NON_PRESENT
;
614 page
= vm_normal_page(vma
, address
, pteval
);
615 if (unlikely(!page
)) {
616 result
= SCAN_PAGE_NULL
;
620 VM_BUG_ON_PAGE(!PageAnon(page
), page
);
622 if (page_mapcount(page
) > 1 &&
623 ++shared
> khugepaged_max_ptes_shared
) {
624 result
= SCAN_EXCEED_SHARED_PTE
;
628 if (PageCompound(page
)) {
630 page
= compound_head(page
);
633 * Check if we have dealt with the compound page
636 list_for_each_entry(p
, compound_pagelist
, lru
) {
643 * We can do it before isolate_lru_page because the
644 * page can't be freed from under us. NOTE: PG_lock
645 * is needed to serialize against split_huge_page
646 * when invoked from the VM.
648 if (!trylock_page(page
)) {
649 result
= SCAN_PAGE_LOCK
;
654 * Check if the page has any GUP (or other external) pins.
656 * The page table that maps the page has been already unlinked
657 * from the page table tree and this process cannot get
658 * an additinal pin on the page.
660 * New pins can come later if the page is shared across fork,
661 * but not from this process. The other process cannot write to
662 * the page, only trigger CoW.
664 if (!is_refcount_suitable(page
)) {
666 result
= SCAN_PAGE_COUNT
;
669 if (!pte_write(pteval
) && PageSwapCache(page
) &&
670 !reuse_swap_page(page
, NULL
)) {
672 * Page is in the swap cache and cannot be re-used.
673 * It cannot be collapsed into a THP.
676 result
= SCAN_SWAP_CACHE_PAGE
;
681 * Isolate the page to avoid collapsing an hugepage
682 * currently in use by the VM.
684 if (isolate_lru_page(page
)) {
686 result
= SCAN_DEL_PAGE_LRU
;
689 mod_node_page_state(page_pgdat(page
),
690 NR_ISOLATED_ANON
+ page_is_file_lru(page
),
692 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
693 VM_BUG_ON_PAGE(PageLRU(page
), page
);
695 if (PageCompound(page
))
696 list_add_tail(&page
->lru
, compound_pagelist
);
698 /* There should be enough young pte to collapse the page */
699 if (pte_young(pteval
) ||
700 page_is_young(page
) || PageReferenced(page
) ||
701 mmu_notifier_test_young(vma
->vm_mm
, address
))
704 if (pte_write(pteval
))
707 if (likely(writable
)) {
708 if (likely(referenced
)) {
709 result
= SCAN_SUCCEED
;
710 trace_mm_collapse_huge_page_isolate(page
, none_or_zero
,
711 referenced
, writable
, result
);
715 result
= SCAN_PAGE_RO
;
719 release_pte_pages(pte
, _pte
, compound_pagelist
);
720 trace_mm_collapse_huge_page_isolate(page
, none_or_zero
,
721 referenced
, writable
, result
);
725 static void __collapse_huge_page_copy(pte_t
*pte
, struct page
*page
,
726 struct vm_area_struct
*vma
,
727 unsigned long address
,
729 struct list_head
*compound_pagelist
)
731 struct page
*src_page
, *tmp
;
733 for (_pte
= pte
; _pte
< pte
+ HPAGE_PMD_NR
;
734 _pte
++, page
++, address
+= PAGE_SIZE
) {
735 pte_t pteval
= *_pte
;
737 if (pte_none(pteval
) || is_zero_pfn(pte_pfn(pteval
))) {
738 clear_user_highpage(page
, address
);
739 add_mm_counter(vma
->vm_mm
, MM_ANONPAGES
, 1);
740 if (is_zero_pfn(pte_pfn(pteval
))) {
742 * ptl mostly unnecessary.
746 * paravirt calls inside pte_clear here are
749 pte_clear(vma
->vm_mm
, address
, _pte
);
753 src_page
= pte_page(pteval
);
754 copy_user_highpage(page
, src_page
, address
, vma
);
755 if (!PageCompound(src_page
))
756 release_pte_page(src_page
);
758 * ptl mostly unnecessary, but preempt has to
759 * be disabled to update the per-cpu stats
760 * inside page_remove_rmap().
764 * paravirt calls inside pte_clear here are
767 pte_clear(vma
->vm_mm
, address
, _pte
);
768 page_remove_rmap(src_page
, false);
770 free_page_and_swap_cache(src_page
);
774 list_for_each_entry_safe(src_page
, tmp
, compound_pagelist
, lru
) {
775 list_del(&src_page
->lru
);
776 release_pte_page(src_page
);
780 static void khugepaged_alloc_sleep(void)
784 add_wait_queue(&khugepaged_wait
, &wait
);
785 freezable_schedule_timeout_interruptible(
786 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs
));
787 remove_wait_queue(&khugepaged_wait
, &wait
);
790 static int khugepaged_node_load
[MAX_NUMNODES
];
792 static bool khugepaged_scan_abort(int nid
)
797 * If node_reclaim_mode is disabled, then no extra effort is made to
798 * allocate memory locally.
800 if (!node_reclaim_mode
)
803 /* If there is a count for this node already, it must be acceptable */
804 if (khugepaged_node_load
[nid
])
807 for (i
= 0; i
< MAX_NUMNODES
; i
++) {
808 if (!khugepaged_node_load
[i
])
810 if (node_distance(nid
, i
) > node_reclaim_distance
)
816 /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */
817 static inline gfp_t
alloc_hugepage_khugepaged_gfpmask(void)
819 return khugepaged_defrag() ? GFP_TRANSHUGE
: GFP_TRANSHUGE_LIGHT
;
823 static int khugepaged_find_target_node(void)
825 static int last_khugepaged_target_node
= NUMA_NO_NODE
;
826 int nid
, target_node
= 0, max_value
= 0;
828 /* find first node with max normal pages hit */
829 for (nid
= 0; nid
< MAX_NUMNODES
; nid
++)
830 if (khugepaged_node_load
[nid
] > max_value
) {
831 max_value
= khugepaged_node_load
[nid
];
835 /* do some balance if several nodes have the same hit record */
836 if (target_node
<= last_khugepaged_target_node
)
837 for (nid
= last_khugepaged_target_node
+ 1; nid
< MAX_NUMNODES
;
839 if (max_value
== khugepaged_node_load
[nid
]) {
844 last_khugepaged_target_node
= target_node
;
848 static bool khugepaged_prealloc_page(struct page
**hpage
, bool *wait
)
850 if (IS_ERR(*hpage
)) {
856 khugepaged_alloc_sleep();
866 khugepaged_alloc_page(struct page
**hpage
, gfp_t gfp
, int node
)
868 VM_BUG_ON_PAGE(*hpage
, *hpage
);
870 *hpage
= __alloc_pages_node(node
, gfp
, HPAGE_PMD_ORDER
);
871 if (unlikely(!*hpage
)) {
872 count_vm_event(THP_COLLAPSE_ALLOC_FAILED
);
873 *hpage
= ERR_PTR(-ENOMEM
);
877 prep_transhuge_page(*hpage
);
878 count_vm_event(THP_COLLAPSE_ALLOC
);
882 static int khugepaged_find_target_node(void)
887 static inline struct page
*alloc_khugepaged_hugepage(void)
891 page
= alloc_pages(alloc_hugepage_khugepaged_gfpmask(),
894 prep_transhuge_page(page
);
898 static struct page
*khugepaged_alloc_hugepage(bool *wait
)
903 hpage
= alloc_khugepaged_hugepage();
905 count_vm_event(THP_COLLAPSE_ALLOC_FAILED
);
910 khugepaged_alloc_sleep();
912 count_vm_event(THP_COLLAPSE_ALLOC
);
913 } while (unlikely(!hpage
) && likely(khugepaged_enabled()));
918 static bool khugepaged_prealloc_page(struct page
**hpage
, bool *wait
)
921 * If the hpage allocated earlier was briefly exposed in page cache
922 * before collapse_file() failed, it is possible that racing lookups
923 * have not yet completed, and would then be unpleasantly surprised by
924 * finding the hpage reused for the same mapping at a different offset.
925 * Just release the previous allocation if there is any danger of that.
927 if (*hpage
&& page_count(*hpage
) > 1) {
933 *hpage
= khugepaged_alloc_hugepage(wait
);
935 if (unlikely(!*hpage
))
942 khugepaged_alloc_page(struct page
**hpage
, gfp_t gfp
, int node
)
951 * If mmap_lock temporarily dropped, revalidate vma
952 * before taking mmap_lock.
953 * Return 0 if succeeds, otherwise return none-zero
957 static int hugepage_vma_revalidate(struct mm_struct
*mm
, unsigned long address
,
958 struct vm_area_struct
**vmap
)
960 struct vm_area_struct
*vma
;
961 unsigned long hstart
, hend
;
963 if (unlikely(khugepaged_test_exit(mm
)))
964 return SCAN_ANY_PROCESS
;
966 *vmap
= vma
= find_vma(mm
, address
);
968 return SCAN_VMA_NULL
;
970 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
971 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
972 if (address
< hstart
|| address
+ HPAGE_PMD_SIZE
> hend
)
973 return SCAN_ADDRESS_RANGE
;
974 if (!hugepage_vma_check(vma
, vma
->vm_flags
))
975 return SCAN_VMA_CHECK
;
976 /* Anon VMA expected */
977 if (!vma
->anon_vma
|| vma
->vm_ops
)
978 return SCAN_VMA_CHECK
;
983 * Bring missing pages in from swap, to complete THP collapse.
984 * Only done if khugepaged_scan_pmd believes it is worthwhile.
986 * Called and returns without pte mapped or spinlocks held,
987 * but with mmap_lock held to protect against vma changes.
990 static bool __collapse_huge_page_swapin(struct mm_struct
*mm
,
991 struct vm_area_struct
*vma
,
992 unsigned long address
, pmd_t
*pmd
,
997 struct vm_fault vmf
= {
1000 .flags
= FAULT_FLAG_ALLOW_RETRY
,
1002 .pgoff
= linear_page_index(vma
, address
),
1005 vmf
.pte
= pte_offset_map(pmd
, address
);
1006 for (; vmf
.address
< address
+ HPAGE_PMD_NR
*PAGE_SIZE
;
1007 vmf
.pte
++, vmf
.address
+= PAGE_SIZE
) {
1008 vmf
.orig_pte
= *vmf
.pte
;
1009 if (!is_swap_pte(vmf
.orig_pte
))
1012 ret
= do_swap_page(&vmf
);
1014 /* do_swap_page returns VM_FAULT_RETRY with released mmap_lock */
1015 if (ret
& VM_FAULT_RETRY
) {
1017 if (hugepage_vma_revalidate(mm
, address
, &vmf
.vma
)) {
1018 /* vma is no longer available, don't continue to swapin */
1019 trace_mm_collapse_huge_page_swapin(mm
, swapped_in
, referenced
, 0);
1022 /* check if the pmd is still valid */
1023 if (mm_find_pmd(mm
, address
) != pmd
) {
1024 trace_mm_collapse_huge_page_swapin(mm
, swapped_in
, referenced
, 0);
1028 if (ret
& VM_FAULT_ERROR
) {
1029 trace_mm_collapse_huge_page_swapin(mm
, swapped_in
, referenced
, 0);
1032 /* pte is unmapped now, we need to map it */
1033 vmf
.pte
= pte_offset_map(pmd
, vmf
.address
);
1038 /* Drain LRU add pagevec to remove extra pin on the swapped in pages */
1042 trace_mm_collapse_huge_page_swapin(mm
, swapped_in
, referenced
, 1);
1046 static void collapse_huge_page(struct mm_struct
*mm
,
1047 unsigned long address
,
1048 struct page
**hpage
,
1049 int node
, int referenced
, int unmapped
)
1051 LIST_HEAD(compound_pagelist
);
1055 struct page
*new_page
;
1056 spinlock_t
*pmd_ptl
, *pte_ptl
;
1057 int isolated
= 0, result
= 0;
1058 struct vm_area_struct
*vma
;
1059 struct mmu_notifier_range range
;
1062 VM_BUG_ON(address
& ~HPAGE_PMD_MASK
);
1064 /* Only allocate from the target node */
1065 gfp
= alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE
;
1068 * Before allocating the hugepage, release the mmap_lock read lock.
1069 * The allocation can take potentially a long time if it involves
1070 * sync compaction, and we do not need to hold the mmap_lock during
1071 * that. We will recheck the vma after taking it again in write mode.
1073 mmap_read_unlock(mm
);
1074 new_page
= khugepaged_alloc_page(hpage
, gfp
, node
);
1076 result
= SCAN_ALLOC_HUGE_PAGE_FAIL
;
1080 if (unlikely(mem_cgroup_charge(new_page
, mm
, gfp
))) {
1081 result
= SCAN_CGROUP_CHARGE_FAIL
;
1084 count_memcg_page_event(new_page
, THP_COLLAPSE_ALLOC
);
1087 result
= hugepage_vma_revalidate(mm
, address
, &vma
);
1089 mmap_read_unlock(mm
);
1093 pmd
= mm_find_pmd(mm
, address
);
1095 result
= SCAN_PMD_NULL
;
1096 mmap_read_unlock(mm
);
1101 * __collapse_huge_page_swapin always returns with mmap_lock locked.
1102 * If it fails, we release mmap_lock and jump out_nolock.
1103 * Continuing to collapse causes inconsistency.
1105 if (unmapped
&& !__collapse_huge_page_swapin(mm
, vma
, address
,
1107 mmap_read_unlock(mm
);
1111 mmap_read_unlock(mm
);
1113 * Prevent all access to pagetables with the exception of
1114 * gup_fast later handled by the ptep_clear_flush and the VM
1115 * handled by the anon_vma lock + PG_lock.
1117 mmap_write_lock(mm
);
1118 result
= hugepage_vma_revalidate(mm
, address
, &vma
);
1121 /* check if the pmd is still valid */
1122 if (mm_find_pmd(mm
, address
) != pmd
)
1125 anon_vma_lock_write(vma
->anon_vma
);
1127 mmu_notifier_range_init(&range
, MMU_NOTIFY_CLEAR
, 0, NULL
, mm
,
1128 address
, address
+ HPAGE_PMD_SIZE
);
1129 mmu_notifier_invalidate_range_start(&range
);
1131 pte
= pte_offset_map(pmd
, address
);
1132 pte_ptl
= pte_lockptr(mm
, pmd
);
1134 pmd_ptl
= pmd_lock(mm
, pmd
); /* probably unnecessary */
1136 * After this gup_fast can't run anymore. This also removes
1137 * any huge TLB entry from the CPU so we won't allow
1138 * huge and small TLB entries for the same virtual address
1139 * to avoid the risk of CPU bugs in that area.
1141 _pmd
= pmdp_collapse_flush(vma
, address
, pmd
);
1142 spin_unlock(pmd_ptl
);
1143 mmu_notifier_invalidate_range_end(&range
);
1146 isolated
= __collapse_huge_page_isolate(vma
, address
, pte
,
1147 &compound_pagelist
);
1148 spin_unlock(pte_ptl
);
1150 if (unlikely(!isolated
)) {
1153 BUG_ON(!pmd_none(*pmd
));
1155 * We can only use set_pmd_at when establishing
1156 * hugepmds and never for establishing regular pmds that
1157 * points to regular pagetables. Use pmd_populate for that
1159 pmd_populate(mm
, pmd
, pmd_pgtable(_pmd
));
1160 spin_unlock(pmd_ptl
);
1161 anon_vma_unlock_write(vma
->anon_vma
);
1167 * All pages are isolated and locked so anon_vma rmap
1168 * can't run anymore.
1170 anon_vma_unlock_write(vma
->anon_vma
);
1172 __collapse_huge_page_copy(pte
, new_page
, vma
, address
, pte_ptl
,
1173 &compound_pagelist
);
1175 __SetPageUptodate(new_page
);
1176 pgtable
= pmd_pgtable(_pmd
);
1178 _pmd
= mk_huge_pmd(new_page
, vma
->vm_page_prot
);
1179 _pmd
= maybe_pmd_mkwrite(pmd_mkdirty(_pmd
), vma
);
1182 * spin_lock() below is not the equivalent of smp_wmb(), so
1183 * this is needed to avoid the copy_huge_page writes to become
1184 * visible after the set_pmd_at() write.
1189 BUG_ON(!pmd_none(*pmd
));
1190 page_add_new_anon_rmap(new_page
, vma
, address
, true);
1191 lru_cache_add_inactive_or_unevictable(new_page
, vma
);
1192 pgtable_trans_huge_deposit(mm
, pmd
, pgtable
);
1193 set_pmd_at(mm
, address
, pmd
, _pmd
);
1194 update_mmu_cache_pmd(vma
, address
, pmd
);
1195 spin_unlock(pmd_ptl
);
1199 khugepaged_pages_collapsed
++;
1200 result
= SCAN_SUCCEED
;
1202 mmap_write_unlock(mm
);
1204 if (!IS_ERR_OR_NULL(*hpage
))
1205 mem_cgroup_uncharge(*hpage
);
1206 trace_mm_collapse_huge_page(mm
, isolated
, result
);
1212 static int khugepaged_scan_pmd(struct mm_struct
*mm
,
1213 struct vm_area_struct
*vma
,
1214 unsigned long address
,
1215 struct page
**hpage
)
1219 int ret
= 0, result
= 0, referenced
= 0;
1220 int none_or_zero
= 0, shared
= 0;
1221 struct page
*page
= NULL
;
1222 unsigned long _address
;
1224 int node
= NUMA_NO_NODE
, unmapped
= 0;
1225 bool writable
= false;
1227 VM_BUG_ON(address
& ~HPAGE_PMD_MASK
);
1229 pmd
= mm_find_pmd(mm
, address
);
1231 result
= SCAN_PMD_NULL
;
1235 memset(khugepaged_node_load
, 0, sizeof(khugepaged_node_load
));
1236 pte
= pte_offset_map_lock(mm
, pmd
, address
, &ptl
);
1237 for (_address
= address
, _pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
;
1238 _pte
++, _address
+= PAGE_SIZE
) {
1239 pte_t pteval
= *_pte
;
1240 if (is_swap_pte(pteval
)) {
1241 if (++unmapped
<= khugepaged_max_ptes_swap
) {
1243 * Always be strict with uffd-wp
1244 * enabled swap entries. Please see
1245 * comment below for pte_uffd_wp().
1247 if (pte_swp_uffd_wp(pteval
)) {
1248 result
= SCAN_PTE_UFFD_WP
;
1253 result
= SCAN_EXCEED_SWAP_PTE
;
1257 if (pte_none(pteval
) || is_zero_pfn(pte_pfn(pteval
))) {
1258 if (!userfaultfd_armed(vma
) &&
1259 ++none_or_zero
<= khugepaged_max_ptes_none
) {
1262 result
= SCAN_EXCEED_NONE_PTE
;
1266 if (!pte_present(pteval
)) {
1267 result
= SCAN_PTE_NON_PRESENT
;
1270 if (pte_uffd_wp(pteval
)) {
1272 * Don't collapse the page if any of the small
1273 * PTEs are armed with uffd write protection.
1274 * Here we can also mark the new huge pmd as
1275 * write protected if any of the small ones is
1276 * marked but that could bring uknown
1277 * userfault messages that falls outside of
1278 * the registered range. So, just be simple.
1280 result
= SCAN_PTE_UFFD_WP
;
1283 if (pte_write(pteval
))
1286 page
= vm_normal_page(vma
, _address
, pteval
);
1287 if (unlikely(!page
)) {
1288 result
= SCAN_PAGE_NULL
;
1292 if (page_mapcount(page
) > 1 &&
1293 ++shared
> khugepaged_max_ptes_shared
) {
1294 result
= SCAN_EXCEED_SHARED_PTE
;
1298 page
= compound_head(page
);
1301 * Record which node the original page is from and save this
1302 * information to khugepaged_node_load[].
1303 * Khupaged will allocate hugepage from the node has the max
1306 node
= page_to_nid(page
);
1307 if (khugepaged_scan_abort(node
)) {
1308 result
= SCAN_SCAN_ABORT
;
1311 khugepaged_node_load
[node
]++;
1312 if (!PageLRU(page
)) {
1313 result
= SCAN_PAGE_LRU
;
1316 if (PageLocked(page
)) {
1317 result
= SCAN_PAGE_LOCK
;
1320 if (!PageAnon(page
)) {
1321 result
= SCAN_PAGE_ANON
;
1326 * Check if the page has any GUP (or other external) pins.
1328 * Here the check is racy it may see totmal_mapcount > refcount
1330 * For example, one process with one forked child process.
1331 * The parent has the PMD split due to MADV_DONTNEED, then
1332 * the child is trying unmap the whole PMD, but khugepaged
1333 * may be scanning the parent between the child has
1334 * PageDoubleMap flag cleared and dec the mapcount. So
1335 * khugepaged may see total_mapcount > refcount.
1337 * But such case is ephemeral we could always retry collapse
1338 * later. However it may report false positive if the page
1339 * has excessive GUP pins (i.e. 512). Anyway the same check
1340 * will be done again later the risk seems low.
1342 if (!is_refcount_suitable(page
)) {
1343 result
= SCAN_PAGE_COUNT
;
1346 if (pte_young(pteval
) ||
1347 page_is_young(page
) || PageReferenced(page
) ||
1348 mmu_notifier_test_young(vma
->vm_mm
, address
))
1352 result
= SCAN_PAGE_RO
;
1353 } else if (!referenced
|| (unmapped
&& referenced
< HPAGE_PMD_NR
/2)) {
1354 result
= SCAN_LACK_REFERENCED_PAGE
;
1356 result
= SCAN_SUCCEED
;
1360 pte_unmap_unlock(pte
, ptl
);
1362 node
= khugepaged_find_target_node();
1363 /* collapse_huge_page will return with the mmap_lock released */
1364 collapse_huge_page(mm
, address
, hpage
, node
,
1365 referenced
, unmapped
);
1368 trace_mm_khugepaged_scan_pmd(mm
, page
, writable
, referenced
,
1369 none_or_zero
, result
, unmapped
);
1373 static void collect_mm_slot(struct mm_slot
*mm_slot
)
1375 struct mm_struct
*mm
= mm_slot
->mm
;
1377 lockdep_assert_held(&khugepaged_mm_lock
);
1379 if (khugepaged_test_exit(mm
)) {
1381 hash_del(&mm_slot
->hash
);
1382 list_del(&mm_slot
->mm_node
);
1385 * Not strictly needed because the mm exited already.
1387 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1390 /* khugepaged_mm_lock actually not necessary for the below */
1391 free_mm_slot(mm_slot
);
1398 * Notify khugepaged that given addr of the mm is pte-mapped THP. Then
1399 * khugepaged should try to collapse the page table.
1401 static int khugepaged_add_pte_mapped_thp(struct mm_struct
*mm
,
1404 struct mm_slot
*mm_slot
;
1406 VM_BUG_ON(addr
& ~HPAGE_PMD_MASK
);
1408 spin_lock(&khugepaged_mm_lock
);
1409 mm_slot
= get_mm_slot(mm
);
1410 if (likely(mm_slot
&& mm_slot
->nr_pte_mapped_thp
< MAX_PTE_MAPPED_THP
))
1411 mm_slot
->pte_mapped_thp
[mm_slot
->nr_pte_mapped_thp
++] = addr
;
1412 spin_unlock(&khugepaged_mm_lock
);
1417 * Try to collapse a pte-mapped THP for mm at address haddr.
1419 * This function checks whether all the PTEs in the PMD are pointing to the
1420 * right THP. If so, retract the page table so the THP can refault in with
1423 void collapse_pte_mapped_thp(struct mm_struct
*mm
, unsigned long addr
)
1425 unsigned long haddr
= addr
& HPAGE_PMD_MASK
;
1426 struct vm_area_struct
*vma
= find_vma(mm
, haddr
);
1428 pte_t
*start_pte
, *pte
;
1434 if (!vma
|| !vma
->vm_file
||
1435 vma
->vm_start
> haddr
|| vma
->vm_end
< haddr
+ HPAGE_PMD_SIZE
)
1439 * This vm_flags may not have VM_HUGEPAGE if the page was not
1440 * collapsed by this mm. But we can still collapse if the page is
1441 * the valid THP. Add extra VM_HUGEPAGE so hugepage_vma_check()
1442 * will not fail the vma for missing VM_HUGEPAGE
1444 if (!hugepage_vma_check(vma
, vma
->vm_flags
| VM_HUGEPAGE
))
1447 hpage
= find_lock_page(vma
->vm_file
->f_mapping
,
1448 linear_page_index(vma
, haddr
));
1452 if (!PageHead(hpage
))
1455 pmd
= mm_find_pmd(mm
, haddr
);
1459 start_pte
= pte_offset_map_lock(mm
, pmd
, haddr
, &ptl
);
1461 /* step 1: check all mapped PTEs are to the right huge page */
1462 for (i
= 0, addr
= haddr
, pte
= start_pte
;
1463 i
< HPAGE_PMD_NR
; i
++, addr
+= PAGE_SIZE
, pte
++) {
1466 /* empty pte, skip */
1470 /* page swapped out, abort */
1471 if (!pte_present(*pte
))
1474 page
= vm_normal_page(vma
, addr
, *pte
);
1477 * Note that uprobe, debugger, or MAP_PRIVATE may change the
1478 * page table, but the new page will not be a subpage of hpage.
1480 if (hpage
+ i
!= page
)
1485 /* step 2: adjust rmap */
1486 for (i
= 0, addr
= haddr
, pte
= start_pte
;
1487 i
< HPAGE_PMD_NR
; i
++, addr
+= PAGE_SIZE
, pte
++) {
1492 page
= vm_normal_page(vma
, addr
, *pte
);
1493 page_remove_rmap(page
, false);
1496 pte_unmap_unlock(start_pte
, ptl
);
1498 /* step 3: set proper refcount and mm_counters. */
1500 page_ref_sub(hpage
, count
);
1501 add_mm_counter(vma
->vm_mm
, mm_counter_file(hpage
), -count
);
1504 /* step 4: collapse pmd */
1505 ptl
= pmd_lock(vma
->vm_mm
, pmd
);
1506 _pmd
= pmdp_collapse_flush(vma
, haddr
, pmd
);
1509 pte_free(mm
, pmd_pgtable(_pmd
));
1517 pte_unmap_unlock(start_pte
, ptl
);
1521 static int khugepaged_collapse_pte_mapped_thps(struct mm_slot
*mm_slot
)
1523 struct mm_struct
*mm
= mm_slot
->mm
;
1526 if (likely(mm_slot
->nr_pte_mapped_thp
== 0))
1529 if (!mmap_write_trylock(mm
))
1532 if (unlikely(khugepaged_test_exit(mm
)))
1535 for (i
= 0; i
< mm_slot
->nr_pte_mapped_thp
; i
++)
1536 collapse_pte_mapped_thp(mm
, mm_slot
->pte_mapped_thp
[i
]);
1539 mm_slot
->nr_pte_mapped_thp
= 0;
1540 mmap_write_unlock(mm
);
1544 static void retract_page_tables(struct address_space
*mapping
, pgoff_t pgoff
)
1546 struct vm_area_struct
*vma
;
1547 struct mm_struct
*mm
;
1551 i_mmap_lock_write(mapping
);
1552 vma_interval_tree_foreach(vma
, &mapping
->i_mmap
, pgoff
, pgoff
) {
1554 * Check vma->anon_vma to exclude MAP_PRIVATE mappings that
1555 * got written to. These VMAs are likely not worth investing
1556 * mmap_write_lock(mm) as PMD-mapping is likely to be split
1559 * Not that vma->anon_vma check is racy: it can be set up after
1560 * the check but before we took mmap_lock by the fault path.
1561 * But page lock would prevent establishing any new ptes of the
1562 * page, so we are safe.
1564 * An alternative would be drop the check, but check that page
1565 * table is clear before calling pmdp_collapse_flush() under
1566 * ptl. It has higher chance to recover THP for the VMA, but
1567 * has higher cost too.
1571 addr
= vma
->vm_start
+ ((pgoff
- vma
->vm_pgoff
) << PAGE_SHIFT
);
1572 if (addr
& ~HPAGE_PMD_MASK
)
1574 if (vma
->vm_end
< addr
+ HPAGE_PMD_SIZE
)
1577 pmd
= mm_find_pmd(mm
, addr
);
1581 * We need exclusive mmap_lock to retract page table.
1583 * We use trylock due to lock inversion: we need to acquire
1584 * mmap_lock while holding page lock. Fault path does it in
1585 * reverse order. Trylock is a way to avoid deadlock.
1587 if (mmap_write_trylock(mm
)) {
1588 if (!khugepaged_test_exit(mm
)) {
1589 spinlock_t
*ptl
= pmd_lock(mm
, pmd
);
1590 /* assume page table is clear */
1591 _pmd
= pmdp_collapse_flush(vma
, addr
, pmd
);
1594 pte_free(mm
, pmd_pgtable(_pmd
));
1596 mmap_write_unlock(mm
);
1598 /* Try again later */
1599 khugepaged_add_pte_mapped_thp(mm
, addr
);
1602 i_mmap_unlock_write(mapping
);
1606 * collapse_file - collapse filemap/tmpfs/shmem pages into huge one.
1608 * Basic scheme is simple, details are more complex:
1609 * - allocate and lock a new huge page;
1610 * - scan page cache replacing old pages with the new one
1611 * + swap/gup in pages if necessary;
1613 * + keep old pages around in case rollback is required;
1614 * - if replacing succeeds:
1617 * + unlock huge page;
1618 * - if replacing failed;
1619 * + put all pages back and unfreeze them;
1620 * + restore gaps in the page cache;
1621 * + unlock and free huge page;
1623 static void collapse_file(struct mm_struct
*mm
,
1624 struct file
*file
, pgoff_t start
,
1625 struct page
**hpage
, int node
)
1627 struct address_space
*mapping
= file
->f_mapping
;
1629 struct page
*new_page
;
1630 pgoff_t index
, end
= start
+ HPAGE_PMD_NR
;
1631 LIST_HEAD(pagelist
);
1632 XA_STATE_ORDER(xas
, &mapping
->i_pages
, start
, HPAGE_PMD_ORDER
);
1633 int nr_none
= 0, result
= SCAN_SUCCEED
;
1634 bool is_shmem
= shmem_file(file
);
1636 VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS
) && !is_shmem
);
1637 VM_BUG_ON(start
& (HPAGE_PMD_NR
- 1));
1639 /* Only allocate from the target node */
1640 gfp
= alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE
;
1642 new_page
= khugepaged_alloc_page(hpage
, gfp
, node
);
1644 result
= SCAN_ALLOC_HUGE_PAGE_FAIL
;
1648 if (unlikely(mem_cgroup_charge(new_page
, mm
, gfp
))) {
1649 result
= SCAN_CGROUP_CHARGE_FAIL
;
1652 count_memcg_page_event(new_page
, THP_COLLAPSE_ALLOC
);
1654 /* This will be less messy when we use multi-index entries */
1657 xas_create_range(&xas
);
1658 if (!xas_error(&xas
))
1660 xas_unlock_irq(&xas
);
1661 if (!xas_nomem(&xas
, GFP_KERNEL
)) {
1667 __SetPageLocked(new_page
);
1669 __SetPageSwapBacked(new_page
);
1670 new_page
->index
= start
;
1671 new_page
->mapping
= mapping
;
1674 * At this point the new_page is locked and not up-to-date.
1675 * It's safe to insert it into the page cache, because nobody would
1676 * be able to map it or use it in another way until we unlock it.
1679 xas_set(&xas
, start
);
1680 for (index
= start
; index
< end
; index
++) {
1681 struct page
*page
= xas_next(&xas
);
1683 VM_BUG_ON(index
!= xas
.xa_index
);
1687 * Stop if extent has been truncated or
1688 * hole-punched, and is now completely
1691 if (index
== start
) {
1692 if (!xas_next_entry(&xas
, end
- 1)) {
1693 result
= SCAN_TRUNCATED
;
1696 xas_set(&xas
, index
);
1698 if (!shmem_charge(mapping
->host
, 1)) {
1702 xas_store(&xas
, new_page
);
1707 if (xa_is_value(page
) || !PageUptodate(page
)) {
1708 xas_unlock_irq(&xas
);
1709 /* swap in or instantiate fallocated page */
1710 if (shmem_getpage(mapping
->host
, index
, &page
,
1715 } else if (trylock_page(page
)) {
1717 xas_unlock_irq(&xas
);
1719 result
= SCAN_PAGE_LOCK
;
1722 } else { /* !is_shmem */
1723 if (!page
|| xa_is_value(page
)) {
1724 xas_unlock_irq(&xas
);
1725 page_cache_sync_readahead(mapping
, &file
->f_ra
,
1728 /* drain pagevecs to help isolate_lru_page() */
1730 page
= find_lock_page(mapping
, index
);
1731 if (unlikely(page
== NULL
)) {
1735 } else if (PageDirty(page
)) {
1737 * khugepaged only works on read-only fd,
1738 * so this page is dirty because it hasn't
1739 * been flushed since first write. There
1740 * won't be new dirty pages.
1742 * Trigger async flush here and hope the
1743 * writeback is done when khugepaged
1744 * revisits this page.
1746 * This is a one-off situation. We are not
1747 * forcing writeback in loop.
1749 xas_unlock_irq(&xas
);
1750 filemap_flush(mapping
);
1753 } else if (trylock_page(page
)) {
1755 xas_unlock_irq(&xas
);
1757 result
= SCAN_PAGE_LOCK
;
1763 * The page must be locked, so we can drop the i_pages lock
1764 * without racing with truncate.
1766 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
1768 /* make sure the page is up to date */
1769 if (unlikely(!PageUptodate(page
))) {
1775 * If file was truncated then extended, or hole-punched, before
1776 * we locked the first page, then a THP might be there already.
1778 if (PageTransCompound(page
)) {
1779 result
= SCAN_PAGE_COMPOUND
;
1783 if (page_mapping(page
) != mapping
) {
1784 result
= SCAN_TRUNCATED
;
1788 if (!is_shmem
&& PageDirty(page
)) {
1790 * khugepaged only works on read-only fd, so this
1791 * page is dirty because it hasn't been flushed
1792 * since first write.
1798 if (isolate_lru_page(page
)) {
1799 result
= SCAN_DEL_PAGE_LRU
;
1803 if (page_has_private(page
) &&
1804 !try_to_release_page(page
, GFP_KERNEL
)) {
1805 result
= SCAN_PAGE_HAS_PRIVATE
;
1806 putback_lru_page(page
);
1810 if (page_mapped(page
))
1811 unmap_mapping_pages(mapping
, index
, 1, false);
1814 xas_set(&xas
, index
);
1816 VM_BUG_ON_PAGE(page
!= xas_load(&xas
), page
);
1817 VM_BUG_ON_PAGE(page_mapped(page
), page
);
1820 * The page is expected to have page_count() == 3:
1821 * - we hold a pin on it;
1822 * - one reference from page cache;
1823 * - one from isolate_lru_page;
1825 if (!page_ref_freeze(page
, 3)) {
1826 result
= SCAN_PAGE_COUNT
;
1827 xas_unlock_irq(&xas
);
1828 putback_lru_page(page
);
1833 * Add the page to the list to be able to undo the collapse if
1834 * something go wrong.
1836 list_add_tail(&page
->lru
, &pagelist
);
1838 /* Finally, replace with the new page. */
1839 xas_store(&xas
, new_page
);
1848 __inc_node_page_state(new_page
, NR_SHMEM_THPS
);
1850 __inc_node_page_state(new_page
, NR_FILE_THPS
);
1851 filemap_nr_thps_inc(mapping
);
1855 __mod_lruvec_page_state(new_page
, NR_FILE_PAGES
, nr_none
);
1857 __mod_lruvec_page_state(new_page
, NR_SHMEM
, nr_none
);
1861 xas_unlock_irq(&xas
);
1864 if (result
== SCAN_SUCCEED
) {
1865 struct page
*page
, *tmp
;
1868 * Replacing old pages with new one has succeeded, now we
1869 * need to copy the content and free the old pages.
1872 list_for_each_entry_safe(page
, tmp
, &pagelist
, lru
) {
1873 while (index
< page
->index
) {
1874 clear_highpage(new_page
+ (index
% HPAGE_PMD_NR
));
1877 copy_highpage(new_page
+ (page
->index
% HPAGE_PMD_NR
),
1879 list_del(&page
->lru
);
1880 page
->mapping
= NULL
;
1881 page_ref_unfreeze(page
, 1);
1882 ClearPageActive(page
);
1883 ClearPageUnevictable(page
);
1888 while (index
< end
) {
1889 clear_highpage(new_page
+ (index
% HPAGE_PMD_NR
));
1893 SetPageUptodate(new_page
);
1894 page_ref_add(new_page
, HPAGE_PMD_NR
- 1);
1896 set_page_dirty(new_page
);
1897 lru_cache_add(new_page
);
1900 * Remove pte page tables, so we can re-fault the page as huge.
1902 retract_page_tables(mapping
, start
);
1905 khugepaged_pages_collapsed
++;
1909 /* Something went wrong: roll back page cache changes */
1911 mapping
->nrpages
-= nr_none
;
1914 shmem_uncharge(mapping
->host
, nr_none
);
1916 xas_set(&xas
, start
);
1917 xas_for_each(&xas
, page
, end
- 1) {
1918 page
= list_first_entry_or_null(&pagelist
,
1920 if (!page
|| xas
.xa_index
< page
->index
) {
1924 /* Put holes back where they were */
1925 xas_store(&xas
, NULL
);
1929 VM_BUG_ON_PAGE(page
->index
!= xas
.xa_index
, page
);
1931 /* Unfreeze the page. */
1932 list_del(&page
->lru
);
1933 page_ref_unfreeze(page
, 2);
1934 xas_store(&xas
, page
);
1936 xas_unlock_irq(&xas
);
1938 putback_lru_page(page
);
1942 xas_unlock_irq(&xas
);
1944 new_page
->mapping
= NULL
;
1947 unlock_page(new_page
);
1949 VM_BUG_ON(!list_empty(&pagelist
));
1950 if (!IS_ERR_OR_NULL(*hpage
))
1951 mem_cgroup_uncharge(*hpage
);
1952 /* TODO: tracepoints */
1955 static void khugepaged_scan_file(struct mm_struct
*mm
,
1956 struct file
*file
, pgoff_t start
, struct page
**hpage
)
1958 struct page
*page
= NULL
;
1959 struct address_space
*mapping
= file
->f_mapping
;
1960 XA_STATE(xas
, &mapping
->i_pages
, start
);
1962 int node
= NUMA_NO_NODE
;
1963 int result
= SCAN_SUCCEED
;
1967 memset(khugepaged_node_load
, 0, sizeof(khugepaged_node_load
));
1969 xas_for_each(&xas
, page
, start
+ HPAGE_PMD_NR
- 1) {
1970 if (xas_retry(&xas
, page
))
1973 if (xa_is_value(page
)) {
1974 if (++swap
> khugepaged_max_ptes_swap
) {
1975 result
= SCAN_EXCEED_SWAP_PTE
;
1981 if (PageTransCompound(page
)) {
1982 result
= SCAN_PAGE_COMPOUND
;
1986 node
= page_to_nid(page
);
1987 if (khugepaged_scan_abort(node
)) {
1988 result
= SCAN_SCAN_ABORT
;
1991 khugepaged_node_load
[node
]++;
1993 if (!PageLRU(page
)) {
1994 result
= SCAN_PAGE_LRU
;
1998 if (page_count(page
) !=
1999 1 + page_mapcount(page
) + page_has_private(page
)) {
2000 result
= SCAN_PAGE_COUNT
;
2005 * We probably should check if the page is referenced here, but
2006 * nobody would transfer pte_young() to PageReferenced() for us.
2007 * And rmap walk here is just too costly...
2012 if (need_resched()) {
2019 if (result
== SCAN_SUCCEED
) {
2020 if (present
< HPAGE_PMD_NR
- khugepaged_max_ptes_none
) {
2021 result
= SCAN_EXCEED_NONE_PTE
;
2023 node
= khugepaged_find_target_node();
2024 collapse_file(mm
, file
, start
, hpage
, node
);
2028 /* TODO: tracepoints */
2031 static void khugepaged_scan_file(struct mm_struct
*mm
,
2032 struct file
*file
, pgoff_t start
, struct page
**hpage
)
2037 static int khugepaged_collapse_pte_mapped_thps(struct mm_slot
*mm_slot
)
2043 static unsigned int khugepaged_scan_mm_slot(unsigned int pages
,
2044 struct page
**hpage
)
2045 __releases(&khugepaged_mm_lock
)
2046 __acquires(&khugepaged_mm_lock
)
2048 struct mm_slot
*mm_slot
;
2049 struct mm_struct
*mm
;
2050 struct vm_area_struct
*vma
;
2054 lockdep_assert_held(&khugepaged_mm_lock
);
2056 if (khugepaged_scan
.mm_slot
)
2057 mm_slot
= khugepaged_scan
.mm_slot
;
2059 mm_slot
= list_entry(khugepaged_scan
.mm_head
.next
,
2060 struct mm_slot
, mm_node
);
2061 khugepaged_scan
.address
= 0;
2062 khugepaged_scan
.mm_slot
= mm_slot
;
2064 spin_unlock(&khugepaged_mm_lock
);
2065 khugepaged_collapse_pte_mapped_thps(mm_slot
);
2069 * Don't wait for semaphore (to avoid long wait times). Just move to
2070 * the next mm on the list.
2073 if (unlikely(!mmap_read_trylock(mm
)))
2074 goto breakouterloop_mmap_lock
;
2075 if (likely(!khugepaged_test_exit(mm
)))
2076 vma
= find_vma(mm
, khugepaged_scan
.address
);
2079 for (; vma
; vma
= vma
->vm_next
) {
2080 unsigned long hstart
, hend
;
2083 if (unlikely(khugepaged_test_exit(mm
))) {
2087 if (!hugepage_vma_check(vma
, vma
->vm_flags
)) {
2092 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
2093 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
2096 if (khugepaged_scan
.address
> hend
)
2098 if (khugepaged_scan
.address
< hstart
)
2099 khugepaged_scan
.address
= hstart
;
2100 VM_BUG_ON(khugepaged_scan
.address
& ~HPAGE_PMD_MASK
);
2101 if (shmem_file(vma
->vm_file
) && !shmem_huge_enabled(vma
))
2104 while (khugepaged_scan
.address
< hend
) {
2107 if (unlikely(khugepaged_test_exit(mm
)))
2108 goto breakouterloop
;
2110 VM_BUG_ON(khugepaged_scan
.address
< hstart
||
2111 khugepaged_scan
.address
+ HPAGE_PMD_SIZE
>
2113 if (IS_ENABLED(CONFIG_SHMEM
) && vma
->vm_file
) {
2114 struct file
*file
= get_file(vma
->vm_file
);
2115 pgoff_t pgoff
= linear_page_index(vma
,
2116 khugepaged_scan
.address
);
2118 mmap_read_unlock(mm
);
2120 khugepaged_scan_file(mm
, file
, pgoff
, hpage
);
2123 ret
= khugepaged_scan_pmd(mm
, vma
,
2124 khugepaged_scan
.address
,
2127 /* move to next address */
2128 khugepaged_scan
.address
+= HPAGE_PMD_SIZE
;
2129 progress
+= HPAGE_PMD_NR
;
2131 /* we released mmap_lock so break loop */
2132 goto breakouterloop_mmap_lock
;
2133 if (progress
>= pages
)
2134 goto breakouterloop
;
2138 mmap_read_unlock(mm
); /* exit_mmap will destroy ptes after this */
2139 breakouterloop_mmap_lock
:
2141 spin_lock(&khugepaged_mm_lock
);
2142 VM_BUG_ON(khugepaged_scan
.mm_slot
!= mm_slot
);
2144 * Release the current mm_slot if this mm is about to die, or
2145 * if we scanned all vmas of this mm.
2147 if (khugepaged_test_exit(mm
) || !vma
) {
2149 * Make sure that if mm_users is reaching zero while
2150 * khugepaged runs here, khugepaged_exit will find
2151 * mm_slot not pointing to the exiting mm.
2153 if (mm_slot
->mm_node
.next
!= &khugepaged_scan
.mm_head
) {
2154 khugepaged_scan
.mm_slot
= list_entry(
2155 mm_slot
->mm_node
.next
,
2156 struct mm_slot
, mm_node
);
2157 khugepaged_scan
.address
= 0;
2159 khugepaged_scan
.mm_slot
= NULL
;
2160 khugepaged_full_scans
++;
2163 collect_mm_slot(mm_slot
);
2169 static int khugepaged_has_work(void)
2171 return !list_empty(&khugepaged_scan
.mm_head
) &&
2172 khugepaged_enabled();
2175 static int khugepaged_wait_event(void)
2177 return !list_empty(&khugepaged_scan
.mm_head
) ||
2178 kthread_should_stop();
2181 static void khugepaged_do_scan(void)
2183 struct page
*hpage
= NULL
;
2184 unsigned int progress
= 0, pass_through_head
= 0;
2185 unsigned int pages
= khugepaged_pages_to_scan
;
2188 barrier(); /* write khugepaged_pages_to_scan to local stack */
2190 lru_add_drain_all();
2192 while (progress
< pages
) {
2193 if (!khugepaged_prealloc_page(&hpage
, &wait
))
2198 if (unlikely(kthread_should_stop() || try_to_freeze()))
2201 spin_lock(&khugepaged_mm_lock
);
2202 if (!khugepaged_scan
.mm_slot
)
2203 pass_through_head
++;
2204 if (khugepaged_has_work() &&
2205 pass_through_head
< 2)
2206 progress
+= khugepaged_scan_mm_slot(pages
- progress
,
2210 spin_unlock(&khugepaged_mm_lock
);
2213 if (!IS_ERR_OR_NULL(hpage
))
2217 static bool khugepaged_should_wakeup(void)
2219 return kthread_should_stop() ||
2220 time_after_eq(jiffies
, khugepaged_sleep_expire
);
2223 static void khugepaged_wait_work(void)
2225 if (khugepaged_has_work()) {
2226 const unsigned long scan_sleep_jiffies
=
2227 msecs_to_jiffies(khugepaged_scan_sleep_millisecs
);
2229 if (!scan_sleep_jiffies
)
2232 khugepaged_sleep_expire
= jiffies
+ scan_sleep_jiffies
;
2233 wait_event_freezable_timeout(khugepaged_wait
,
2234 khugepaged_should_wakeup(),
2235 scan_sleep_jiffies
);
2239 if (khugepaged_enabled())
2240 wait_event_freezable(khugepaged_wait
, khugepaged_wait_event());
2243 static int khugepaged(void *none
)
2245 struct mm_slot
*mm_slot
;
2248 set_user_nice(current
, MAX_NICE
);
2250 while (!kthread_should_stop()) {
2251 khugepaged_do_scan();
2252 khugepaged_wait_work();
2255 spin_lock(&khugepaged_mm_lock
);
2256 mm_slot
= khugepaged_scan
.mm_slot
;
2257 khugepaged_scan
.mm_slot
= NULL
;
2259 collect_mm_slot(mm_slot
);
2260 spin_unlock(&khugepaged_mm_lock
);
2264 static void set_recommended_min_free_kbytes(void)
2268 unsigned long recommended_min
;
2270 for_each_populated_zone(zone
) {
2272 * We don't need to worry about fragmentation of
2273 * ZONE_MOVABLE since it only has movable pages.
2275 if (zone_idx(zone
) > gfp_zone(GFP_USER
))
2281 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */
2282 recommended_min
= pageblock_nr_pages
* nr_zones
* 2;
2285 * Make sure that on average at least two pageblocks are almost free
2286 * of another type, one for a migratetype to fall back to and a
2287 * second to avoid subsequent fallbacks of other types There are 3
2288 * MIGRATE_TYPES we care about.
2290 recommended_min
+= pageblock_nr_pages
* nr_zones
*
2291 MIGRATE_PCPTYPES
* MIGRATE_PCPTYPES
;
2293 /* don't ever allow to reserve more than 5% of the lowmem */
2294 recommended_min
= min(recommended_min
,
2295 (unsigned long) nr_free_buffer_pages() / 20);
2296 recommended_min
<<= (PAGE_SHIFT
-10);
2298 if (recommended_min
> min_free_kbytes
) {
2299 if (user_min_free_kbytes
>= 0)
2300 pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n",
2301 min_free_kbytes
, recommended_min
);
2303 min_free_kbytes
= recommended_min
;
2305 setup_per_zone_wmarks();
2308 int start_stop_khugepaged(void)
2312 mutex_lock(&khugepaged_mutex
);
2313 if (khugepaged_enabled()) {
2314 if (!khugepaged_thread
)
2315 khugepaged_thread
= kthread_run(khugepaged
, NULL
,
2317 if (IS_ERR(khugepaged_thread
)) {
2318 pr_err("khugepaged: kthread_run(khugepaged) failed\n");
2319 err
= PTR_ERR(khugepaged_thread
);
2320 khugepaged_thread
= NULL
;
2324 if (!list_empty(&khugepaged_scan
.mm_head
))
2325 wake_up_interruptible(&khugepaged_wait
);
2327 set_recommended_min_free_kbytes();
2328 } else if (khugepaged_thread
) {
2329 kthread_stop(khugepaged_thread
);
2330 khugepaged_thread
= NULL
;
2333 mutex_unlock(&khugepaged_mutex
);
2337 void khugepaged_min_free_kbytes_update(void)
2339 mutex_lock(&khugepaged_mutex
);
2340 if (khugepaged_enabled() && khugepaged_thread
)
2341 set_recommended_min_free_kbytes();
2342 mutex_unlock(&khugepaged_mutex
);