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 /* default scan 8*512 pte (or vmas) every 30 second */
60 static unsigned int khugepaged_pages_to_scan __read_mostly
;
61 static unsigned int khugepaged_pages_collapsed
;
62 static unsigned int khugepaged_full_scans
;
63 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly
= 10000;
64 /* during fragmentation poll the hugepage allocator once every minute */
65 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly
= 60000;
66 static unsigned long khugepaged_sleep_expire
;
67 static DEFINE_SPINLOCK(khugepaged_mm_lock
);
68 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait
);
70 * default collapse hugepages if there is at least one pte mapped like
71 * it would have happened if the vma was large enough during page
74 static unsigned int khugepaged_max_ptes_none __read_mostly
;
75 static unsigned int khugepaged_max_ptes_swap __read_mostly
;
76 static unsigned int khugepaged_max_ptes_shared __read_mostly
;
78 #define MM_SLOTS_HASH_BITS 10
79 static __read_mostly
DEFINE_HASHTABLE(mm_slots_hash
, MM_SLOTS_HASH_BITS
);
81 static struct kmem_cache
*mm_slot_cache __read_mostly
;
83 #define MAX_PTE_MAPPED_THP 8
86 * struct mm_slot - hash lookup from mm to mm_slot
87 * @hash: hash collision list
88 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
89 * @mm: the mm that this information is valid for
92 struct hlist_node hash
;
93 struct list_head mm_node
;
96 /* pte-mapped THP in this mm */
97 int nr_pte_mapped_thp
;
98 unsigned long pte_mapped_thp
[MAX_PTE_MAPPED_THP
];
102 * struct khugepaged_scan - cursor for scanning
103 * @mm_head: the head of the mm list to scan
104 * @mm_slot: the current mm_slot we are scanning
105 * @address: the next address inside that to be scanned
107 * There is only the one khugepaged_scan instance of this cursor structure.
109 struct khugepaged_scan
{
110 struct list_head mm_head
;
111 struct mm_slot
*mm_slot
;
112 unsigned long address
;
115 static struct khugepaged_scan khugepaged_scan
= {
116 .mm_head
= LIST_HEAD_INIT(khugepaged_scan
.mm_head
),
120 static ssize_t
scan_sleep_millisecs_show(struct kobject
*kobj
,
121 struct kobj_attribute
*attr
,
124 return sprintf(buf
, "%u\n", khugepaged_scan_sleep_millisecs
);
127 static ssize_t
scan_sleep_millisecs_store(struct kobject
*kobj
,
128 struct kobj_attribute
*attr
,
129 const char *buf
, size_t count
)
134 err
= kstrtoul(buf
, 10, &msecs
);
135 if (err
|| msecs
> UINT_MAX
)
138 khugepaged_scan_sleep_millisecs
= msecs
;
139 khugepaged_sleep_expire
= 0;
140 wake_up_interruptible(&khugepaged_wait
);
144 static struct kobj_attribute scan_sleep_millisecs_attr
=
145 __ATTR(scan_sleep_millisecs
, 0644, scan_sleep_millisecs_show
,
146 scan_sleep_millisecs_store
);
148 static ssize_t
alloc_sleep_millisecs_show(struct kobject
*kobj
,
149 struct kobj_attribute
*attr
,
152 return sprintf(buf
, "%u\n", khugepaged_alloc_sleep_millisecs
);
155 static ssize_t
alloc_sleep_millisecs_store(struct kobject
*kobj
,
156 struct kobj_attribute
*attr
,
157 const char *buf
, size_t count
)
162 err
= kstrtoul(buf
, 10, &msecs
);
163 if (err
|| msecs
> UINT_MAX
)
166 khugepaged_alloc_sleep_millisecs
= msecs
;
167 khugepaged_sleep_expire
= 0;
168 wake_up_interruptible(&khugepaged_wait
);
172 static struct kobj_attribute alloc_sleep_millisecs_attr
=
173 __ATTR(alloc_sleep_millisecs
, 0644, alloc_sleep_millisecs_show
,
174 alloc_sleep_millisecs_store
);
176 static ssize_t
pages_to_scan_show(struct kobject
*kobj
,
177 struct kobj_attribute
*attr
,
180 return sprintf(buf
, "%u\n", khugepaged_pages_to_scan
);
182 static ssize_t
pages_to_scan_store(struct kobject
*kobj
,
183 struct kobj_attribute
*attr
,
184 const char *buf
, size_t count
)
189 err
= kstrtoul(buf
, 10, &pages
);
190 if (err
|| !pages
|| pages
> UINT_MAX
)
193 khugepaged_pages_to_scan
= pages
;
197 static struct kobj_attribute pages_to_scan_attr
=
198 __ATTR(pages_to_scan
, 0644, pages_to_scan_show
,
199 pages_to_scan_store
);
201 static ssize_t
pages_collapsed_show(struct kobject
*kobj
,
202 struct kobj_attribute
*attr
,
205 return sprintf(buf
, "%u\n", khugepaged_pages_collapsed
);
207 static struct kobj_attribute pages_collapsed_attr
=
208 __ATTR_RO(pages_collapsed
);
210 static ssize_t
full_scans_show(struct kobject
*kobj
,
211 struct kobj_attribute
*attr
,
214 return sprintf(buf
, "%u\n", khugepaged_full_scans
);
216 static struct kobj_attribute full_scans_attr
=
217 __ATTR_RO(full_scans
);
219 static ssize_t
khugepaged_defrag_show(struct kobject
*kobj
,
220 struct kobj_attribute
*attr
, char *buf
)
222 return single_hugepage_flag_show(kobj
, attr
, buf
,
223 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG
);
225 static ssize_t
khugepaged_defrag_store(struct kobject
*kobj
,
226 struct kobj_attribute
*attr
,
227 const char *buf
, size_t count
)
229 return single_hugepage_flag_store(kobj
, attr
, buf
, count
,
230 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG
);
232 static struct kobj_attribute khugepaged_defrag_attr
=
233 __ATTR(defrag
, 0644, khugepaged_defrag_show
,
234 khugepaged_defrag_store
);
237 * max_ptes_none controls if khugepaged should collapse hugepages over
238 * any unmapped ptes in turn potentially increasing the memory
239 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
240 * reduce the available free memory in the system as it
241 * runs. Increasing max_ptes_none will instead potentially reduce the
242 * free memory in the system during the khugepaged scan.
244 static ssize_t
khugepaged_max_ptes_none_show(struct kobject
*kobj
,
245 struct kobj_attribute
*attr
,
248 return sprintf(buf
, "%u\n", khugepaged_max_ptes_none
);
250 static ssize_t
khugepaged_max_ptes_none_store(struct kobject
*kobj
,
251 struct kobj_attribute
*attr
,
252 const char *buf
, size_t count
)
255 unsigned long max_ptes_none
;
257 err
= kstrtoul(buf
, 10, &max_ptes_none
);
258 if (err
|| max_ptes_none
> HPAGE_PMD_NR
-1)
261 khugepaged_max_ptes_none
= max_ptes_none
;
265 static struct kobj_attribute khugepaged_max_ptes_none_attr
=
266 __ATTR(max_ptes_none
, 0644, khugepaged_max_ptes_none_show
,
267 khugepaged_max_ptes_none_store
);
269 static ssize_t
khugepaged_max_ptes_swap_show(struct kobject
*kobj
,
270 struct kobj_attribute
*attr
,
273 return sprintf(buf
, "%u\n", khugepaged_max_ptes_swap
);
276 static ssize_t
khugepaged_max_ptes_swap_store(struct kobject
*kobj
,
277 struct kobj_attribute
*attr
,
278 const char *buf
, size_t count
)
281 unsigned long max_ptes_swap
;
283 err
= kstrtoul(buf
, 10, &max_ptes_swap
);
284 if (err
|| max_ptes_swap
> HPAGE_PMD_NR
-1)
287 khugepaged_max_ptes_swap
= max_ptes_swap
;
292 static struct kobj_attribute khugepaged_max_ptes_swap_attr
=
293 __ATTR(max_ptes_swap
, 0644, khugepaged_max_ptes_swap_show
,
294 khugepaged_max_ptes_swap_store
);
296 static ssize_t
khugepaged_max_ptes_shared_show(struct kobject
*kobj
,
297 struct kobj_attribute
*attr
,
300 return sprintf(buf
, "%u\n", khugepaged_max_ptes_shared
);
303 static ssize_t
khugepaged_max_ptes_shared_store(struct kobject
*kobj
,
304 struct kobj_attribute
*attr
,
305 const char *buf
, size_t count
)
308 unsigned long max_ptes_shared
;
310 err
= kstrtoul(buf
, 10, &max_ptes_shared
);
311 if (err
|| max_ptes_shared
> HPAGE_PMD_NR
-1)
314 khugepaged_max_ptes_shared
= max_ptes_shared
;
319 static struct kobj_attribute khugepaged_max_ptes_shared_attr
=
320 __ATTR(max_ptes_shared
, 0644, khugepaged_max_ptes_shared_show
,
321 khugepaged_max_ptes_shared_store
);
323 static struct attribute
*khugepaged_attr
[] = {
324 &khugepaged_defrag_attr
.attr
,
325 &khugepaged_max_ptes_none_attr
.attr
,
326 &khugepaged_max_ptes_swap_attr
.attr
,
327 &khugepaged_max_ptes_shared_attr
.attr
,
328 &pages_to_scan_attr
.attr
,
329 &pages_collapsed_attr
.attr
,
330 &full_scans_attr
.attr
,
331 &scan_sleep_millisecs_attr
.attr
,
332 &alloc_sleep_millisecs_attr
.attr
,
336 struct attribute_group khugepaged_attr_group
= {
337 .attrs
= khugepaged_attr
,
338 .name
= "khugepaged",
340 #endif /* CONFIG_SYSFS */
342 int hugepage_madvise(struct vm_area_struct
*vma
,
343 unsigned long *vm_flags
, int advice
)
349 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
350 * can't handle this properly after s390_enable_sie, so we simply
351 * ignore the madvise to prevent qemu from causing a SIGSEGV.
353 if (mm_has_pgste(vma
->vm_mm
))
356 *vm_flags
&= ~VM_NOHUGEPAGE
;
357 *vm_flags
|= VM_HUGEPAGE
;
359 * If the vma become good for khugepaged to scan,
360 * register it here without waiting a page fault that
361 * may not happen any time soon.
363 if (!(*vm_flags
& VM_NO_KHUGEPAGED
) &&
364 khugepaged_enter_vma_merge(vma
, *vm_flags
))
367 case MADV_NOHUGEPAGE
:
368 *vm_flags
&= ~VM_HUGEPAGE
;
369 *vm_flags
|= VM_NOHUGEPAGE
;
371 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
372 * this vma even if we leave the mm registered in khugepaged if
373 * it got registered before VM_NOHUGEPAGE was set.
381 int __init
khugepaged_init(void)
383 mm_slot_cache
= kmem_cache_create("khugepaged_mm_slot",
384 sizeof(struct mm_slot
),
385 __alignof__(struct mm_slot
), 0, NULL
);
389 khugepaged_pages_to_scan
= HPAGE_PMD_NR
* 8;
390 khugepaged_max_ptes_none
= HPAGE_PMD_NR
- 1;
391 khugepaged_max_ptes_swap
= HPAGE_PMD_NR
/ 8;
392 khugepaged_max_ptes_shared
= HPAGE_PMD_NR
/ 2;
397 void __init
khugepaged_destroy(void)
399 kmem_cache_destroy(mm_slot_cache
);
402 static inline struct mm_slot
*alloc_mm_slot(void)
404 if (!mm_slot_cache
) /* initialization failed */
406 return kmem_cache_zalloc(mm_slot_cache
, GFP_KERNEL
);
409 static inline void free_mm_slot(struct mm_slot
*mm_slot
)
411 kmem_cache_free(mm_slot_cache
, mm_slot
);
414 static struct mm_slot
*get_mm_slot(struct mm_struct
*mm
)
416 struct mm_slot
*mm_slot
;
418 hash_for_each_possible(mm_slots_hash
, mm_slot
, hash
, (unsigned long)mm
)
419 if (mm
== mm_slot
->mm
)
425 static void insert_to_mm_slots_hash(struct mm_struct
*mm
,
426 struct mm_slot
*mm_slot
)
429 hash_add(mm_slots_hash
, &mm_slot
->hash
, (long)mm
);
432 static inline int khugepaged_test_exit(struct mm_struct
*mm
)
434 return atomic_read(&mm
->mm_users
) == 0;
437 static bool hugepage_vma_check(struct vm_area_struct
*vma
,
438 unsigned long vm_flags
)
440 if ((!(vm_flags
& VM_HUGEPAGE
) && !khugepaged_always()) ||
441 (vm_flags
& VM_NOHUGEPAGE
) ||
442 test_bit(MMF_DISABLE_THP
, &vma
->vm_mm
->flags
))
445 if (shmem_file(vma
->vm_file
) ||
446 (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS
) &&
448 (vm_flags
& VM_DENYWRITE
))) {
449 return IS_ALIGNED((vma
->vm_start
>> PAGE_SHIFT
) - vma
->vm_pgoff
,
452 if (!vma
->anon_vma
|| vma
->vm_ops
)
454 if (vma_is_temporary_stack(vma
))
456 return !(vm_flags
& VM_NO_KHUGEPAGED
);
459 int __khugepaged_enter(struct mm_struct
*mm
)
461 struct mm_slot
*mm_slot
;
464 mm_slot
= alloc_mm_slot();
468 /* __khugepaged_exit() must not run from under us */
469 VM_BUG_ON_MM(khugepaged_test_exit(mm
), mm
);
470 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE
, &mm
->flags
))) {
471 free_mm_slot(mm_slot
);
475 spin_lock(&khugepaged_mm_lock
);
476 insert_to_mm_slots_hash(mm
, mm_slot
);
478 * Insert just behind the scanning cursor, to let the area settle
481 wakeup
= list_empty(&khugepaged_scan
.mm_head
);
482 list_add_tail(&mm_slot
->mm_node
, &khugepaged_scan
.mm_head
);
483 spin_unlock(&khugepaged_mm_lock
);
487 wake_up_interruptible(&khugepaged_wait
);
492 int khugepaged_enter_vma_merge(struct vm_area_struct
*vma
,
493 unsigned long vm_flags
)
495 unsigned long hstart
, hend
;
498 * khugepaged only supports read-only files for non-shmem files.
499 * khugepaged does not yet work on special mappings. And
500 * file-private shmem THP is not supported.
502 if (!hugepage_vma_check(vma
, vm_flags
))
505 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
506 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
508 return khugepaged_enter(vma
, vm_flags
);
512 void __khugepaged_exit(struct mm_struct
*mm
)
514 struct mm_slot
*mm_slot
;
517 spin_lock(&khugepaged_mm_lock
);
518 mm_slot
= get_mm_slot(mm
);
519 if (mm_slot
&& khugepaged_scan
.mm_slot
!= mm_slot
) {
520 hash_del(&mm_slot
->hash
);
521 list_del(&mm_slot
->mm_node
);
524 spin_unlock(&khugepaged_mm_lock
);
527 clear_bit(MMF_VM_HUGEPAGE
, &mm
->flags
);
528 free_mm_slot(mm_slot
);
530 } else if (mm_slot
) {
532 * This is required to serialize against
533 * khugepaged_test_exit() (which is guaranteed to run
534 * under mmap sem read mode). Stop here (after we
535 * return all pagetables will be destroyed) until
536 * khugepaged has finished working on the pagetables
537 * under the mmap_sem.
539 down_write(&mm
->mmap_sem
);
540 up_write(&mm
->mmap_sem
);
544 static void release_pte_page(struct page
*page
)
546 mod_node_page_state(page_pgdat(page
),
547 NR_ISOLATED_ANON
+ page_is_file_lru(page
),
550 putback_lru_page(page
);
553 static void release_pte_pages(pte_t
*pte
, pte_t
*_pte
,
554 struct list_head
*compound_pagelist
)
556 struct page
*page
, *tmp
;
558 while (--_pte
>= pte
) {
559 pte_t pteval
= *_pte
;
561 page
= pte_page(pteval
);
562 if (!pte_none(pteval
) && !is_zero_pfn(pte_pfn(pteval
)) &&
564 release_pte_page(page
);
567 list_for_each_entry_safe(page
, tmp
, compound_pagelist
, lru
) {
568 list_del(&page
->lru
);
569 release_pte_page(page
);
573 static bool is_refcount_suitable(struct page
*page
)
575 int expected_refcount
;
577 expected_refcount
= total_mapcount(page
);
578 if (PageSwapCache(page
))
579 expected_refcount
+= compound_nr(page
);
581 return page_count(page
) == expected_refcount
;
584 static int __collapse_huge_page_isolate(struct vm_area_struct
*vma
,
585 unsigned long address
,
587 struct list_head
*compound_pagelist
)
589 struct page
*page
= NULL
;
591 int none_or_zero
= 0, shared
= 0, result
= 0, referenced
= 0;
592 bool writable
= false;
594 for (_pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
;
595 _pte
++, address
+= PAGE_SIZE
) {
596 pte_t pteval
= *_pte
;
597 if (pte_none(pteval
) || (pte_present(pteval
) &&
598 is_zero_pfn(pte_pfn(pteval
)))) {
599 if (!userfaultfd_armed(vma
) &&
600 ++none_or_zero
<= khugepaged_max_ptes_none
) {
603 result
= SCAN_EXCEED_NONE_PTE
;
607 if (!pte_present(pteval
)) {
608 result
= SCAN_PTE_NON_PRESENT
;
611 page
= vm_normal_page(vma
, address
, pteval
);
612 if (unlikely(!page
)) {
613 result
= SCAN_PAGE_NULL
;
617 VM_BUG_ON_PAGE(!PageAnon(page
), page
);
619 if (page_mapcount(page
) > 1 &&
620 ++shared
> khugepaged_max_ptes_shared
) {
621 result
= SCAN_EXCEED_SHARED_PTE
;
625 if (PageCompound(page
)) {
627 page
= compound_head(page
);
630 * Check if we have dealt with the compound page
633 list_for_each_entry(p
, compound_pagelist
, lru
) {
640 * We can do it before isolate_lru_page because the
641 * page can't be freed from under us. NOTE: PG_lock
642 * is needed to serialize against split_huge_page
643 * when invoked from the VM.
645 if (!trylock_page(page
)) {
646 result
= SCAN_PAGE_LOCK
;
651 * Check if the page has any GUP (or other external) pins.
653 * The page table that maps the page has been already unlinked
654 * from the page table tree and this process cannot get
655 * an additinal pin on the page.
657 * New pins can come later if the page is shared across fork,
658 * but not from this process. The other process cannot write to
659 * the page, only trigger CoW.
661 if (!is_refcount_suitable(page
)) {
663 result
= SCAN_PAGE_COUNT
;
666 if (!pte_write(pteval
) && PageSwapCache(page
) &&
667 !reuse_swap_page(page
, NULL
)) {
669 * Page is in the swap cache and cannot be re-used.
670 * It cannot be collapsed into a THP.
673 result
= SCAN_SWAP_CACHE_PAGE
;
678 * Isolate the page to avoid collapsing an hugepage
679 * currently in use by the VM.
681 if (isolate_lru_page(page
)) {
683 result
= SCAN_DEL_PAGE_LRU
;
686 mod_node_page_state(page_pgdat(page
),
687 NR_ISOLATED_ANON
+ page_is_file_lru(page
),
689 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
690 VM_BUG_ON_PAGE(PageLRU(page
), page
);
692 if (PageCompound(page
))
693 list_add_tail(&page
->lru
, compound_pagelist
);
695 /* There should be enough young pte to collapse the page */
696 if (pte_young(pteval
) ||
697 page_is_young(page
) || PageReferenced(page
) ||
698 mmu_notifier_test_young(vma
->vm_mm
, address
))
701 if (pte_write(pteval
))
704 if (likely(writable
)) {
705 if (likely(referenced
)) {
706 result
= SCAN_SUCCEED
;
707 trace_mm_collapse_huge_page_isolate(page
, none_or_zero
,
708 referenced
, writable
, result
);
712 result
= SCAN_PAGE_RO
;
716 release_pte_pages(pte
, _pte
, compound_pagelist
);
717 trace_mm_collapse_huge_page_isolate(page
, none_or_zero
,
718 referenced
, writable
, result
);
722 static void __collapse_huge_page_copy(pte_t
*pte
, struct page
*page
,
723 struct vm_area_struct
*vma
,
724 unsigned long address
,
726 struct list_head
*compound_pagelist
)
728 struct page
*src_page
, *tmp
;
730 for (_pte
= pte
; _pte
< pte
+ HPAGE_PMD_NR
;
731 _pte
++, page
++, address
+= PAGE_SIZE
) {
732 pte_t pteval
= *_pte
;
734 if (pte_none(pteval
) || is_zero_pfn(pte_pfn(pteval
))) {
735 clear_user_highpage(page
, address
);
736 add_mm_counter(vma
->vm_mm
, MM_ANONPAGES
, 1);
737 if (is_zero_pfn(pte_pfn(pteval
))) {
739 * ptl mostly unnecessary.
743 * paravirt calls inside pte_clear here are
746 pte_clear(vma
->vm_mm
, address
, _pte
);
750 src_page
= pte_page(pteval
);
751 copy_user_highpage(page
, src_page
, address
, vma
);
752 if (!PageCompound(src_page
))
753 release_pte_page(src_page
);
755 * ptl mostly unnecessary, but preempt has to
756 * be disabled to update the per-cpu stats
757 * inside page_remove_rmap().
761 * paravirt calls inside pte_clear here are
764 pte_clear(vma
->vm_mm
, address
, _pte
);
765 page_remove_rmap(src_page
, false);
767 free_page_and_swap_cache(src_page
);
771 list_for_each_entry_safe(src_page
, tmp
, compound_pagelist
, lru
) {
772 list_del(&src_page
->lru
);
773 release_pte_page(src_page
);
777 static void khugepaged_alloc_sleep(void)
781 add_wait_queue(&khugepaged_wait
, &wait
);
782 freezable_schedule_timeout_interruptible(
783 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs
));
784 remove_wait_queue(&khugepaged_wait
, &wait
);
787 static int khugepaged_node_load
[MAX_NUMNODES
];
789 static bool khugepaged_scan_abort(int nid
)
794 * If node_reclaim_mode is disabled, then no extra effort is made to
795 * allocate memory locally.
797 if (!node_reclaim_mode
)
800 /* If there is a count for this node already, it must be acceptable */
801 if (khugepaged_node_load
[nid
])
804 for (i
= 0; i
< MAX_NUMNODES
; i
++) {
805 if (!khugepaged_node_load
[i
])
807 if (node_distance(nid
, i
) > node_reclaim_distance
)
813 /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */
814 static inline gfp_t
alloc_hugepage_khugepaged_gfpmask(void)
816 return khugepaged_defrag() ? GFP_TRANSHUGE
: GFP_TRANSHUGE_LIGHT
;
820 static int khugepaged_find_target_node(void)
822 static int last_khugepaged_target_node
= NUMA_NO_NODE
;
823 int nid
, target_node
= 0, max_value
= 0;
825 /* find first node with max normal pages hit */
826 for (nid
= 0; nid
< MAX_NUMNODES
; nid
++)
827 if (khugepaged_node_load
[nid
] > max_value
) {
828 max_value
= khugepaged_node_load
[nid
];
832 /* do some balance if several nodes have the same hit record */
833 if (target_node
<= last_khugepaged_target_node
)
834 for (nid
= last_khugepaged_target_node
+ 1; nid
< MAX_NUMNODES
;
836 if (max_value
== khugepaged_node_load
[nid
]) {
841 last_khugepaged_target_node
= target_node
;
845 static bool khugepaged_prealloc_page(struct page
**hpage
, bool *wait
)
847 if (IS_ERR(*hpage
)) {
853 khugepaged_alloc_sleep();
863 khugepaged_alloc_page(struct page
**hpage
, gfp_t gfp
, int node
)
865 VM_BUG_ON_PAGE(*hpage
, *hpage
);
867 *hpage
= __alloc_pages_node(node
, gfp
, HPAGE_PMD_ORDER
);
868 if (unlikely(!*hpage
)) {
869 count_vm_event(THP_COLLAPSE_ALLOC_FAILED
);
870 *hpage
= ERR_PTR(-ENOMEM
);
874 prep_transhuge_page(*hpage
);
875 count_vm_event(THP_COLLAPSE_ALLOC
);
879 static int khugepaged_find_target_node(void)
884 static inline struct page
*alloc_khugepaged_hugepage(void)
888 page
= alloc_pages(alloc_hugepage_khugepaged_gfpmask(),
891 prep_transhuge_page(page
);
895 static struct page
*khugepaged_alloc_hugepage(bool *wait
)
900 hpage
= alloc_khugepaged_hugepage();
902 count_vm_event(THP_COLLAPSE_ALLOC_FAILED
);
907 khugepaged_alloc_sleep();
909 count_vm_event(THP_COLLAPSE_ALLOC
);
910 } while (unlikely(!hpage
) && likely(khugepaged_enabled()));
915 static bool khugepaged_prealloc_page(struct page
**hpage
, bool *wait
)
918 *hpage
= khugepaged_alloc_hugepage(wait
);
920 if (unlikely(!*hpage
))
927 khugepaged_alloc_page(struct page
**hpage
, gfp_t gfp
, int node
)
936 * If mmap_sem temporarily dropped, revalidate vma
937 * before taking mmap_sem.
938 * Return 0 if succeeds, otherwise return none-zero
942 static int hugepage_vma_revalidate(struct mm_struct
*mm
, unsigned long address
,
943 struct vm_area_struct
**vmap
)
945 struct vm_area_struct
*vma
;
946 unsigned long hstart
, hend
;
948 if (unlikely(khugepaged_test_exit(mm
)))
949 return SCAN_ANY_PROCESS
;
951 *vmap
= vma
= find_vma(mm
, address
);
953 return SCAN_VMA_NULL
;
955 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
956 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
957 if (address
< hstart
|| address
+ HPAGE_PMD_SIZE
> hend
)
958 return SCAN_ADDRESS_RANGE
;
959 if (!hugepage_vma_check(vma
, vma
->vm_flags
))
960 return SCAN_VMA_CHECK
;
965 * Bring missing pages in from swap, to complete THP collapse.
966 * Only done if khugepaged_scan_pmd believes it is worthwhile.
968 * Called and returns without pte mapped or spinlocks held,
969 * but with mmap_sem held to protect against vma changes.
972 static bool __collapse_huge_page_swapin(struct mm_struct
*mm
,
973 struct vm_area_struct
*vma
,
974 unsigned long address
, pmd_t
*pmd
,
979 struct vm_fault vmf
= {
982 .flags
= FAULT_FLAG_ALLOW_RETRY
,
984 .pgoff
= linear_page_index(vma
, address
),
987 vmf
.pte
= pte_offset_map(pmd
, address
);
988 for (; vmf
.address
< address
+ HPAGE_PMD_NR
*PAGE_SIZE
;
989 vmf
.pte
++, vmf
.address
+= PAGE_SIZE
) {
990 vmf
.orig_pte
= *vmf
.pte
;
991 if (!is_swap_pte(vmf
.orig_pte
))
994 ret
= do_swap_page(&vmf
);
996 /* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */
997 if (ret
& VM_FAULT_RETRY
) {
998 down_read(&mm
->mmap_sem
);
999 if (hugepage_vma_revalidate(mm
, address
, &vmf
.vma
)) {
1000 /* vma is no longer available, don't continue to swapin */
1001 trace_mm_collapse_huge_page_swapin(mm
, swapped_in
, referenced
, 0);
1004 /* check if the pmd is still valid */
1005 if (mm_find_pmd(mm
, address
) != pmd
) {
1006 trace_mm_collapse_huge_page_swapin(mm
, swapped_in
, referenced
, 0);
1010 if (ret
& VM_FAULT_ERROR
) {
1011 trace_mm_collapse_huge_page_swapin(mm
, swapped_in
, referenced
, 0);
1014 /* pte is unmapped now, we need to map it */
1015 vmf
.pte
= pte_offset_map(pmd
, vmf
.address
);
1020 /* Drain LRU add pagevec to remove extra pin on the swapped in pages */
1024 trace_mm_collapse_huge_page_swapin(mm
, swapped_in
, referenced
, 1);
1028 static void collapse_huge_page(struct mm_struct
*mm
,
1029 unsigned long address
,
1030 struct page
**hpage
,
1031 int node
, int referenced
, int unmapped
)
1033 LIST_HEAD(compound_pagelist
);
1037 struct page
*new_page
;
1038 spinlock_t
*pmd_ptl
, *pte_ptl
;
1039 int isolated
= 0, result
= 0;
1040 struct vm_area_struct
*vma
;
1041 struct mmu_notifier_range range
;
1044 VM_BUG_ON(address
& ~HPAGE_PMD_MASK
);
1046 /* Only allocate from the target node */
1047 gfp
= alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE
;
1050 * Before allocating the hugepage, release the mmap_sem read lock.
1051 * The allocation can take potentially a long time if it involves
1052 * sync compaction, and we do not need to hold the mmap_sem during
1053 * that. We will recheck the vma after taking it again in write mode.
1055 up_read(&mm
->mmap_sem
);
1056 new_page
= khugepaged_alloc_page(hpage
, gfp
, node
);
1058 result
= SCAN_ALLOC_HUGE_PAGE_FAIL
;
1062 if (unlikely(mem_cgroup_charge(new_page
, mm
, gfp
))) {
1063 result
= SCAN_CGROUP_CHARGE_FAIL
;
1066 count_memcg_page_event(new_page
, THP_COLLAPSE_ALLOC
);
1068 down_read(&mm
->mmap_sem
);
1069 result
= hugepage_vma_revalidate(mm
, address
, &vma
);
1071 up_read(&mm
->mmap_sem
);
1075 pmd
= mm_find_pmd(mm
, address
);
1077 result
= SCAN_PMD_NULL
;
1078 up_read(&mm
->mmap_sem
);
1083 * __collapse_huge_page_swapin always returns with mmap_sem locked.
1084 * If it fails, we release mmap_sem and jump out_nolock.
1085 * Continuing to collapse causes inconsistency.
1087 if (unmapped
&& !__collapse_huge_page_swapin(mm
, vma
, address
,
1089 up_read(&mm
->mmap_sem
);
1093 up_read(&mm
->mmap_sem
);
1095 * Prevent all access to pagetables with the exception of
1096 * gup_fast later handled by the ptep_clear_flush and the VM
1097 * handled by the anon_vma lock + PG_lock.
1099 down_write(&mm
->mmap_sem
);
1100 result
= SCAN_ANY_PROCESS
;
1101 if (!mmget_still_valid(mm
))
1103 result
= hugepage_vma_revalidate(mm
, address
, &vma
);
1106 /* check if the pmd is still valid */
1107 if (mm_find_pmd(mm
, address
) != pmd
)
1110 anon_vma_lock_write(vma
->anon_vma
);
1112 mmu_notifier_range_init(&range
, MMU_NOTIFY_CLEAR
, 0, NULL
, mm
,
1113 address
, address
+ HPAGE_PMD_SIZE
);
1114 mmu_notifier_invalidate_range_start(&range
);
1116 pte
= pte_offset_map(pmd
, address
);
1117 pte_ptl
= pte_lockptr(mm
, pmd
);
1119 pmd_ptl
= pmd_lock(mm
, pmd
); /* probably unnecessary */
1121 * After this gup_fast can't run anymore. This also removes
1122 * any huge TLB entry from the CPU so we won't allow
1123 * huge and small TLB entries for the same virtual address
1124 * to avoid the risk of CPU bugs in that area.
1126 _pmd
= pmdp_collapse_flush(vma
, address
, pmd
);
1127 spin_unlock(pmd_ptl
);
1128 mmu_notifier_invalidate_range_end(&range
);
1131 isolated
= __collapse_huge_page_isolate(vma
, address
, pte
,
1132 &compound_pagelist
);
1133 spin_unlock(pte_ptl
);
1135 if (unlikely(!isolated
)) {
1138 BUG_ON(!pmd_none(*pmd
));
1140 * We can only use set_pmd_at when establishing
1141 * hugepmds and never for establishing regular pmds that
1142 * points to regular pagetables. Use pmd_populate for that
1144 pmd_populate(mm
, pmd
, pmd_pgtable(_pmd
));
1145 spin_unlock(pmd_ptl
);
1146 anon_vma_unlock_write(vma
->anon_vma
);
1152 * All pages are isolated and locked so anon_vma rmap
1153 * can't run anymore.
1155 anon_vma_unlock_write(vma
->anon_vma
);
1157 __collapse_huge_page_copy(pte
, new_page
, vma
, address
, pte_ptl
,
1158 &compound_pagelist
);
1160 __SetPageUptodate(new_page
);
1161 pgtable
= pmd_pgtable(_pmd
);
1163 _pmd
= mk_huge_pmd(new_page
, vma
->vm_page_prot
);
1164 _pmd
= maybe_pmd_mkwrite(pmd_mkdirty(_pmd
), vma
);
1167 * spin_lock() below is not the equivalent of smp_wmb(), so
1168 * this is needed to avoid the copy_huge_page writes to become
1169 * visible after the set_pmd_at() write.
1174 BUG_ON(!pmd_none(*pmd
));
1175 page_add_new_anon_rmap(new_page
, vma
, address
, true);
1176 lru_cache_add_active_or_unevictable(new_page
, vma
);
1177 pgtable_trans_huge_deposit(mm
, pmd
, pgtable
);
1178 set_pmd_at(mm
, address
, pmd
, _pmd
);
1179 update_mmu_cache_pmd(vma
, address
, pmd
);
1180 spin_unlock(pmd_ptl
);
1184 khugepaged_pages_collapsed
++;
1185 result
= SCAN_SUCCEED
;
1187 up_write(&mm
->mmap_sem
);
1189 if (!IS_ERR_OR_NULL(*hpage
))
1190 mem_cgroup_uncharge(*hpage
);
1191 trace_mm_collapse_huge_page(mm
, isolated
, result
);
1197 static int khugepaged_scan_pmd(struct mm_struct
*mm
,
1198 struct vm_area_struct
*vma
,
1199 unsigned long address
,
1200 struct page
**hpage
)
1204 int ret
= 0, result
= 0, referenced
= 0;
1205 int none_or_zero
= 0, shared
= 0;
1206 struct page
*page
= NULL
;
1207 unsigned long _address
;
1209 int node
= NUMA_NO_NODE
, unmapped
= 0;
1210 bool writable
= false;
1212 VM_BUG_ON(address
& ~HPAGE_PMD_MASK
);
1214 pmd
= mm_find_pmd(mm
, address
);
1216 result
= SCAN_PMD_NULL
;
1220 memset(khugepaged_node_load
, 0, sizeof(khugepaged_node_load
));
1221 pte
= pte_offset_map_lock(mm
, pmd
, address
, &ptl
);
1222 for (_address
= address
, _pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
;
1223 _pte
++, _address
+= PAGE_SIZE
) {
1224 pte_t pteval
= *_pte
;
1225 if (is_swap_pte(pteval
)) {
1226 if (++unmapped
<= khugepaged_max_ptes_swap
) {
1228 * Always be strict with uffd-wp
1229 * enabled swap entries. Please see
1230 * comment below for pte_uffd_wp().
1232 if (pte_swp_uffd_wp(pteval
)) {
1233 result
= SCAN_PTE_UFFD_WP
;
1238 result
= SCAN_EXCEED_SWAP_PTE
;
1242 if (pte_none(pteval
) || is_zero_pfn(pte_pfn(pteval
))) {
1243 if (!userfaultfd_armed(vma
) &&
1244 ++none_or_zero
<= khugepaged_max_ptes_none
) {
1247 result
= SCAN_EXCEED_NONE_PTE
;
1251 if (!pte_present(pteval
)) {
1252 result
= SCAN_PTE_NON_PRESENT
;
1255 if (pte_uffd_wp(pteval
)) {
1257 * Don't collapse the page if any of the small
1258 * PTEs are armed with uffd write protection.
1259 * Here we can also mark the new huge pmd as
1260 * write protected if any of the small ones is
1261 * marked but that could bring uknown
1262 * userfault messages that falls outside of
1263 * the registered range. So, just be simple.
1265 result
= SCAN_PTE_UFFD_WP
;
1268 if (pte_write(pteval
))
1271 page
= vm_normal_page(vma
, _address
, pteval
);
1272 if (unlikely(!page
)) {
1273 result
= SCAN_PAGE_NULL
;
1277 if (page_mapcount(page
) > 1 &&
1278 ++shared
> khugepaged_max_ptes_shared
) {
1279 result
= SCAN_EXCEED_SHARED_PTE
;
1283 page
= compound_head(page
);
1286 * Record which node the original page is from and save this
1287 * information to khugepaged_node_load[].
1288 * Khupaged will allocate hugepage from the node has the max
1291 node
= page_to_nid(page
);
1292 if (khugepaged_scan_abort(node
)) {
1293 result
= SCAN_SCAN_ABORT
;
1296 khugepaged_node_load
[node
]++;
1297 if (!PageLRU(page
)) {
1298 result
= SCAN_PAGE_LRU
;
1301 if (PageLocked(page
)) {
1302 result
= SCAN_PAGE_LOCK
;
1305 if (!PageAnon(page
)) {
1306 result
= SCAN_PAGE_ANON
;
1311 * Check if the page has any GUP (or other external) pins.
1313 * Here the check is racy it may see totmal_mapcount > refcount
1315 * For example, one process with one forked child process.
1316 * The parent has the PMD split due to MADV_DONTNEED, then
1317 * the child is trying unmap the whole PMD, but khugepaged
1318 * may be scanning the parent between the child has
1319 * PageDoubleMap flag cleared and dec the mapcount. So
1320 * khugepaged may see total_mapcount > refcount.
1322 * But such case is ephemeral we could always retry collapse
1323 * later. However it may report false positive if the page
1324 * has excessive GUP pins (i.e. 512). Anyway the same check
1325 * will be done again later the risk seems low.
1327 if (!is_refcount_suitable(page
)) {
1328 result
= SCAN_PAGE_COUNT
;
1331 if (pte_young(pteval
) ||
1332 page_is_young(page
) || PageReferenced(page
) ||
1333 mmu_notifier_test_young(vma
->vm_mm
, address
))
1337 result
= SCAN_PAGE_RO
;
1338 } else if (!referenced
|| (unmapped
&& referenced
< HPAGE_PMD_NR
/2)) {
1339 result
= SCAN_LACK_REFERENCED_PAGE
;
1341 result
= SCAN_SUCCEED
;
1345 pte_unmap_unlock(pte
, ptl
);
1347 node
= khugepaged_find_target_node();
1348 /* collapse_huge_page will return with the mmap_sem released */
1349 collapse_huge_page(mm
, address
, hpage
, node
,
1350 referenced
, unmapped
);
1353 trace_mm_khugepaged_scan_pmd(mm
, page
, writable
, referenced
,
1354 none_or_zero
, result
, unmapped
);
1358 static void collect_mm_slot(struct mm_slot
*mm_slot
)
1360 struct mm_struct
*mm
= mm_slot
->mm
;
1362 lockdep_assert_held(&khugepaged_mm_lock
);
1364 if (khugepaged_test_exit(mm
)) {
1366 hash_del(&mm_slot
->hash
);
1367 list_del(&mm_slot
->mm_node
);
1370 * Not strictly needed because the mm exited already.
1372 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1375 /* khugepaged_mm_lock actually not necessary for the below */
1376 free_mm_slot(mm_slot
);
1383 * Notify khugepaged that given addr of the mm is pte-mapped THP. Then
1384 * khugepaged should try to collapse the page table.
1386 static int khugepaged_add_pte_mapped_thp(struct mm_struct
*mm
,
1389 struct mm_slot
*mm_slot
;
1391 VM_BUG_ON(addr
& ~HPAGE_PMD_MASK
);
1393 spin_lock(&khugepaged_mm_lock
);
1394 mm_slot
= get_mm_slot(mm
);
1395 if (likely(mm_slot
&& mm_slot
->nr_pte_mapped_thp
< MAX_PTE_MAPPED_THP
))
1396 mm_slot
->pte_mapped_thp
[mm_slot
->nr_pte_mapped_thp
++] = addr
;
1397 spin_unlock(&khugepaged_mm_lock
);
1402 * Try to collapse a pte-mapped THP for mm at address haddr.
1404 * This function checks whether all the PTEs in the PMD are pointing to the
1405 * right THP. If so, retract the page table so the THP can refault in with
1408 void collapse_pte_mapped_thp(struct mm_struct
*mm
, unsigned long addr
)
1410 unsigned long haddr
= addr
& HPAGE_PMD_MASK
;
1411 struct vm_area_struct
*vma
= find_vma(mm
, haddr
);
1412 struct page
*hpage
= NULL
;
1413 pte_t
*start_pte
, *pte
;
1419 if (!vma
|| !vma
->vm_file
||
1420 vma
->vm_start
> haddr
|| vma
->vm_end
< haddr
+ HPAGE_PMD_SIZE
)
1424 * This vm_flags may not have VM_HUGEPAGE if the page was not
1425 * collapsed by this mm. But we can still collapse if the page is
1426 * the valid THP. Add extra VM_HUGEPAGE so hugepage_vma_check()
1427 * will not fail the vma for missing VM_HUGEPAGE
1429 if (!hugepage_vma_check(vma
, vma
->vm_flags
| VM_HUGEPAGE
))
1432 pmd
= mm_find_pmd(mm
, haddr
);
1436 start_pte
= pte_offset_map_lock(mm
, pmd
, haddr
, &ptl
);
1438 /* step 1: check all mapped PTEs are to the right huge page */
1439 for (i
= 0, addr
= haddr
, pte
= start_pte
;
1440 i
< HPAGE_PMD_NR
; i
++, addr
+= PAGE_SIZE
, pte
++) {
1443 /* empty pte, skip */
1447 /* page swapped out, abort */
1448 if (!pte_present(*pte
))
1451 page
= vm_normal_page(vma
, addr
, *pte
);
1453 if (!page
|| !PageCompound(page
))
1457 hpage
= compound_head(page
);
1459 * The mapping of the THP should not change.
1461 * Note that uprobe, debugger, or MAP_PRIVATE may
1462 * change the page table, but the new page will
1463 * not pass PageCompound() check.
1465 if (WARN_ON(hpage
->mapping
!= vma
->vm_file
->f_mapping
))
1470 * Confirm the page maps to the correct subpage.
1472 * Note that uprobe, debugger, or MAP_PRIVATE may change
1473 * the page table, but the new page will not pass
1474 * PageCompound() check.
1476 if (WARN_ON(hpage
+ i
!= page
))
1481 /* step 2: adjust rmap */
1482 for (i
= 0, addr
= haddr
, pte
= start_pte
;
1483 i
< HPAGE_PMD_NR
; i
++, addr
+= PAGE_SIZE
, pte
++) {
1488 page
= vm_normal_page(vma
, addr
, *pte
);
1489 page_remove_rmap(page
, false);
1492 pte_unmap_unlock(start_pte
, ptl
);
1494 /* step 3: set proper refcount and mm_counters. */
1496 page_ref_sub(hpage
, count
);
1497 add_mm_counter(vma
->vm_mm
, mm_counter_file(hpage
), -count
);
1500 /* step 4: collapse pmd */
1501 ptl
= pmd_lock(vma
->vm_mm
, pmd
);
1502 _pmd
= pmdp_collapse_flush(vma
, addr
, pmd
);
1505 pte_free(mm
, pmd_pgtable(_pmd
));
1509 pte_unmap_unlock(start_pte
, ptl
);
1512 static int khugepaged_collapse_pte_mapped_thps(struct mm_slot
*mm_slot
)
1514 struct mm_struct
*mm
= mm_slot
->mm
;
1517 if (likely(mm_slot
->nr_pte_mapped_thp
== 0))
1520 if (!down_write_trylock(&mm
->mmap_sem
))
1523 if (unlikely(khugepaged_test_exit(mm
)))
1526 for (i
= 0; i
< mm_slot
->nr_pte_mapped_thp
; i
++)
1527 collapse_pte_mapped_thp(mm
, mm_slot
->pte_mapped_thp
[i
]);
1530 mm_slot
->nr_pte_mapped_thp
= 0;
1531 up_write(&mm
->mmap_sem
);
1535 static void retract_page_tables(struct address_space
*mapping
, pgoff_t pgoff
)
1537 struct vm_area_struct
*vma
;
1541 i_mmap_lock_write(mapping
);
1542 vma_interval_tree_foreach(vma
, &mapping
->i_mmap
, pgoff
, pgoff
) {
1544 * Check vma->anon_vma to exclude MAP_PRIVATE mappings that
1545 * got written to. These VMAs are likely not worth investing
1546 * down_write(mmap_sem) as PMD-mapping is likely to be split
1549 * Not that vma->anon_vma check is racy: it can be set up after
1550 * the check but before we took mmap_sem by the fault path.
1551 * But page lock would prevent establishing any new ptes of the
1552 * page, so we are safe.
1554 * An alternative would be drop the check, but check that page
1555 * table is clear before calling pmdp_collapse_flush() under
1556 * ptl. It has higher chance to recover THP for the VMA, but
1557 * has higher cost too.
1561 addr
= vma
->vm_start
+ ((pgoff
- vma
->vm_pgoff
) << PAGE_SHIFT
);
1562 if (addr
& ~HPAGE_PMD_MASK
)
1564 if (vma
->vm_end
< addr
+ HPAGE_PMD_SIZE
)
1566 pmd
= mm_find_pmd(vma
->vm_mm
, addr
);
1570 * We need exclusive mmap_sem to retract page table.
1572 * We use trylock due to lock inversion: we need to acquire
1573 * mmap_sem while holding page lock. Fault path does it in
1574 * reverse order. Trylock is a way to avoid deadlock.
1576 if (down_write_trylock(&vma
->vm_mm
->mmap_sem
)) {
1577 spinlock_t
*ptl
= pmd_lock(vma
->vm_mm
, pmd
);
1578 /* assume page table is clear */
1579 _pmd
= pmdp_collapse_flush(vma
, addr
, pmd
);
1581 up_write(&vma
->vm_mm
->mmap_sem
);
1582 mm_dec_nr_ptes(vma
->vm_mm
);
1583 pte_free(vma
->vm_mm
, pmd_pgtable(_pmd
));
1585 /* Try again later */
1586 khugepaged_add_pte_mapped_thp(vma
->vm_mm
, addr
);
1589 i_mmap_unlock_write(mapping
);
1593 * collapse_file - collapse filemap/tmpfs/shmem pages into huge one.
1595 * Basic scheme is simple, details are more complex:
1596 * - allocate and lock a new huge page;
1597 * - scan page cache replacing old pages with the new one
1598 * + swap/gup in pages if necessary;
1600 * + keep old pages around in case rollback is required;
1601 * - if replacing succeeds:
1604 * + unlock huge page;
1605 * - if replacing failed;
1606 * + put all pages back and unfreeze them;
1607 * + restore gaps in the page cache;
1608 * + unlock and free huge page;
1610 static void collapse_file(struct mm_struct
*mm
,
1611 struct file
*file
, pgoff_t start
,
1612 struct page
**hpage
, int node
)
1614 struct address_space
*mapping
= file
->f_mapping
;
1616 struct page
*new_page
;
1617 pgoff_t index
, end
= start
+ HPAGE_PMD_NR
;
1618 LIST_HEAD(pagelist
);
1619 XA_STATE_ORDER(xas
, &mapping
->i_pages
, start
, HPAGE_PMD_ORDER
);
1620 int nr_none
= 0, result
= SCAN_SUCCEED
;
1621 bool is_shmem
= shmem_file(file
);
1623 VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS
) && !is_shmem
);
1624 VM_BUG_ON(start
& (HPAGE_PMD_NR
- 1));
1626 /* Only allocate from the target node */
1627 gfp
= alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE
;
1629 new_page
= khugepaged_alloc_page(hpage
, gfp
, node
);
1631 result
= SCAN_ALLOC_HUGE_PAGE_FAIL
;
1635 if (unlikely(mem_cgroup_charge(new_page
, mm
, gfp
))) {
1636 result
= SCAN_CGROUP_CHARGE_FAIL
;
1639 count_memcg_page_event(new_page
, THP_COLLAPSE_ALLOC
);
1641 /* This will be less messy when we use multi-index entries */
1644 xas_create_range(&xas
);
1645 if (!xas_error(&xas
))
1647 xas_unlock_irq(&xas
);
1648 if (!xas_nomem(&xas
, GFP_KERNEL
)) {
1654 __SetPageLocked(new_page
);
1656 __SetPageSwapBacked(new_page
);
1657 new_page
->index
= start
;
1658 new_page
->mapping
= mapping
;
1661 * At this point the new_page is locked and not up-to-date.
1662 * It's safe to insert it into the page cache, because nobody would
1663 * be able to map it or use it in another way until we unlock it.
1666 xas_set(&xas
, start
);
1667 for (index
= start
; index
< end
; index
++) {
1668 struct page
*page
= xas_next(&xas
);
1670 VM_BUG_ON(index
!= xas
.xa_index
);
1674 * Stop if extent has been truncated or
1675 * hole-punched, and is now completely
1678 if (index
== start
) {
1679 if (!xas_next_entry(&xas
, end
- 1)) {
1680 result
= SCAN_TRUNCATED
;
1683 xas_set(&xas
, index
);
1685 if (!shmem_charge(mapping
->host
, 1)) {
1689 xas_store(&xas
, new_page
);
1694 if (xa_is_value(page
) || !PageUptodate(page
)) {
1695 xas_unlock_irq(&xas
);
1696 /* swap in or instantiate fallocated page */
1697 if (shmem_getpage(mapping
->host
, index
, &page
,
1702 } else if (trylock_page(page
)) {
1704 xas_unlock_irq(&xas
);
1706 result
= SCAN_PAGE_LOCK
;
1709 } else { /* !is_shmem */
1710 if (!page
|| xa_is_value(page
)) {
1711 xas_unlock_irq(&xas
);
1712 page_cache_sync_readahead(mapping
, &file
->f_ra
,
1715 /* drain pagevecs to help isolate_lru_page() */
1717 page
= find_lock_page(mapping
, index
);
1718 if (unlikely(page
== NULL
)) {
1722 } else if (PageDirty(page
)) {
1724 * khugepaged only works on read-only fd,
1725 * so this page is dirty because it hasn't
1726 * been flushed since first write. There
1727 * won't be new dirty pages.
1729 * Trigger async flush here and hope the
1730 * writeback is done when khugepaged
1731 * revisits this page.
1733 * This is a one-off situation. We are not
1734 * forcing writeback in loop.
1736 xas_unlock_irq(&xas
);
1737 filemap_flush(mapping
);
1740 } else if (trylock_page(page
)) {
1742 xas_unlock_irq(&xas
);
1744 result
= SCAN_PAGE_LOCK
;
1750 * The page must be locked, so we can drop the i_pages lock
1751 * without racing with truncate.
1753 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
1755 /* make sure the page is up to date */
1756 if (unlikely(!PageUptodate(page
))) {
1762 * If file was truncated then extended, or hole-punched, before
1763 * we locked the first page, then a THP might be there already.
1765 if (PageTransCompound(page
)) {
1766 result
= SCAN_PAGE_COMPOUND
;
1770 if (page_mapping(page
) != mapping
) {
1771 result
= SCAN_TRUNCATED
;
1775 if (!is_shmem
&& PageDirty(page
)) {
1777 * khugepaged only works on read-only fd, so this
1778 * page is dirty because it hasn't been flushed
1779 * since first write.
1785 if (isolate_lru_page(page
)) {
1786 result
= SCAN_DEL_PAGE_LRU
;
1790 if (page_has_private(page
) &&
1791 !try_to_release_page(page
, GFP_KERNEL
)) {
1792 result
= SCAN_PAGE_HAS_PRIVATE
;
1793 putback_lru_page(page
);
1797 if (page_mapped(page
))
1798 unmap_mapping_pages(mapping
, index
, 1, false);
1801 xas_set(&xas
, index
);
1803 VM_BUG_ON_PAGE(page
!= xas_load(&xas
), page
);
1804 VM_BUG_ON_PAGE(page_mapped(page
), page
);
1807 * The page is expected to have page_count() == 3:
1808 * - we hold a pin on it;
1809 * - one reference from page cache;
1810 * - one from isolate_lru_page;
1812 if (!page_ref_freeze(page
, 3)) {
1813 result
= SCAN_PAGE_COUNT
;
1814 xas_unlock_irq(&xas
);
1815 putback_lru_page(page
);
1820 * Add the page to the list to be able to undo the collapse if
1821 * something go wrong.
1823 list_add_tail(&page
->lru
, &pagelist
);
1825 /* Finally, replace with the new page. */
1826 xas_store(&xas
, new_page
);
1835 __inc_node_page_state(new_page
, NR_SHMEM_THPS
);
1837 __inc_node_page_state(new_page
, NR_FILE_THPS
);
1838 filemap_nr_thps_inc(mapping
);
1842 __mod_lruvec_page_state(new_page
, NR_FILE_PAGES
, nr_none
);
1844 __mod_lruvec_page_state(new_page
, NR_SHMEM
, nr_none
);
1848 xas_unlock_irq(&xas
);
1851 if (result
== SCAN_SUCCEED
) {
1852 struct page
*page
, *tmp
;
1855 * Replacing old pages with new one has succeeded, now we
1856 * need to copy the content and free the old pages.
1859 list_for_each_entry_safe(page
, tmp
, &pagelist
, lru
) {
1860 while (index
< page
->index
) {
1861 clear_highpage(new_page
+ (index
% HPAGE_PMD_NR
));
1864 copy_highpage(new_page
+ (page
->index
% HPAGE_PMD_NR
),
1866 list_del(&page
->lru
);
1867 page
->mapping
= NULL
;
1868 page_ref_unfreeze(page
, 1);
1869 ClearPageActive(page
);
1870 ClearPageUnevictable(page
);
1875 while (index
< end
) {
1876 clear_highpage(new_page
+ (index
% HPAGE_PMD_NR
));
1880 SetPageUptodate(new_page
);
1881 page_ref_add(new_page
, HPAGE_PMD_NR
- 1);
1883 set_page_dirty(new_page
);
1884 lru_cache_add(new_page
);
1887 * Remove pte page tables, so we can re-fault the page as huge.
1889 retract_page_tables(mapping
, start
);
1892 khugepaged_pages_collapsed
++;
1896 /* Something went wrong: roll back page cache changes */
1898 mapping
->nrpages
-= nr_none
;
1901 shmem_uncharge(mapping
->host
, nr_none
);
1903 xas_set(&xas
, start
);
1904 xas_for_each(&xas
, page
, end
- 1) {
1905 page
= list_first_entry_or_null(&pagelist
,
1907 if (!page
|| xas
.xa_index
< page
->index
) {
1911 /* Put holes back where they were */
1912 xas_store(&xas
, NULL
);
1916 VM_BUG_ON_PAGE(page
->index
!= xas
.xa_index
, page
);
1918 /* Unfreeze the page. */
1919 list_del(&page
->lru
);
1920 page_ref_unfreeze(page
, 2);
1921 xas_store(&xas
, page
);
1923 xas_unlock_irq(&xas
);
1925 putback_lru_page(page
);
1929 xas_unlock_irq(&xas
);
1931 new_page
->mapping
= NULL
;
1934 unlock_page(new_page
);
1936 VM_BUG_ON(!list_empty(&pagelist
));
1937 if (!IS_ERR_OR_NULL(*hpage
))
1938 mem_cgroup_uncharge(*hpage
);
1939 /* TODO: tracepoints */
1942 static void khugepaged_scan_file(struct mm_struct
*mm
,
1943 struct file
*file
, pgoff_t start
, struct page
**hpage
)
1945 struct page
*page
= NULL
;
1946 struct address_space
*mapping
= file
->f_mapping
;
1947 XA_STATE(xas
, &mapping
->i_pages
, start
);
1949 int node
= NUMA_NO_NODE
;
1950 int result
= SCAN_SUCCEED
;
1954 memset(khugepaged_node_load
, 0, sizeof(khugepaged_node_load
));
1956 xas_for_each(&xas
, page
, start
+ HPAGE_PMD_NR
- 1) {
1957 if (xas_retry(&xas
, page
))
1960 if (xa_is_value(page
)) {
1961 if (++swap
> khugepaged_max_ptes_swap
) {
1962 result
= SCAN_EXCEED_SWAP_PTE
;
1968 if (PageTransCompound(page
)) {
1969 result
= SCAN_PAGE_COMPOUND
;
1973 node
= page_to_nid(page
);
1974 if (khugepaged_scan_abort(node
)) {
1975 result
= SCAN_SCAN_ABORT
;
1978 khugepaged_node_load
[node
]++;
1980 if (!PageLRU(page
)) {
1981 result
= SCAN_PAGE_LRU
;
1985 if (page_count(page
) !=
1986 1 + page_mapcount(page
) + page_has_private(page
)) {
1987 result
= SCAN_PAGE_COUNT
;
1992 * We probably should check if the page is referenced here, but
1993 * nobody would transfer pte_young() to PageReferenced() for us.
1994 * And rmap walk here is just too costly...
1999 if (need_resched()) {
2006 if (result
== SCAN_SUCCEED
) {
2007 if (present
< HPAGE_PMD_NR
- khugepaged_max_ptes_none
) {
2008 result
= SCAN_EXCEED_NONE_PTE
;
2010 node
= khugepaged_find_target_node();
2011 collapse_file(mm
, file
, start
, hpage
, node
);
2015 /* TODO: tracepoints */
2018 static void khugepaged_scan_file(struct mm_struct
*mm
,
2019 struct file
*file
, pgoff_t start
, struct page
**hpage
)
2024 static int khugepaged_collapse_pte_mapped_thps(struct mm_slot
*mm_slot
)
2030 static unsigned int khugepaged_scan_mm_slot(unsigned int pages
,
2031 struct page
**hpage
)
2032 __releases(&khugepaged_mm_lock
)
2033 __acquires(&khugepaged_mm_lock
)
2035 struct mm_slot
*mm_slot
;
2036 struct mm_struct
*mm
;
2037 struct vm_area_struct
*vma
;
2041 lockdep_assert_held(&khugepaged_mm_lock
);
2043 if (khugepaged_scan
.mm_slot
)
2044 mm_slot
= khugepaged_scan
.mm_slot
;
2046 mm_slot
= list_entry(khugepaged_scan
.mm_head
.next
,
2047 struct mm_slot
, mm_node
);
2048 khugepaged_scan
.address
= 0;
2049 khugepaged_scan
.mm_slot
= mm_slot
;
2051 spin_unlock(&khugepaged_mm_lock
);
2052 khugepaged_collapse_pte_mapped_thps(mm_slot
);
2056 * Don't wait for semaphore (to avoid long wait times). Just move to
2057 * the next mm on the list.
2060 if (unlikely(!down_read_trylock(&mm
->mmap_sem
)))
2061 goto breakouterloop_mmap_sem
;
2062 if (likely(!khugepaged_test_exit(mm
)))
2063 vma
= find_vma(mm
, khugepaged_scan
.address
);
2066 for (; vma
; vma
= vma
->vm_next
) {
2067 unsigned long hstart
, hend
;
2070 if (unlikely(khugepaged_test_exit(mm
))) {
2074 if (!hugepage_vma_check(vma
, vma
->vm_flags
)) {
2079 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
2080 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
2083 if (khugepaged_scan
.address
> hend
)
2085 if (khugepaged_scan
.address
< hstart
)
2086 khugepaged_scan
.address
= hstart
;
2087 VM_BUG_ON(khugepaged_scan
.address
& ~HPAGE_PMD_MASK
);
2088 if (shmem_file(vma
->vm_file
) && !shmem_huge_enabled(vma
))
2091 while (khugepaged_scan
.address
< hend
) {
2094 if (unlikely(khugepaged_test_exit(mm
)))
2095 goto breakouterloop
;
2097 VM_BUG_ON(khugepaged_scan
.address
< hstart
||
2098 khugepaged_scan
.address
+ HPAGE_PMD_SIZE
>
2100 if (IS_ENABLED(CONFIG_SHMEM
) && vma
->vm_file
) {
2101 struct file
*file
= get_file(vma
->vm_file
);
2102 pgoff_t pgoff
= linear_page_index(vma
,
2103 khugepaged_scan
.address
);
2105 up_read(&mm
->mmap_sem
);
2107 khugepaged_scan_file(mm
, file
, pgoff
, hpage
);
2110 ret
= khugepaged_scan_pmd(mm
, vma
,
2111 khugepaged_scan
.address
,
2114 /* move to next address */
2115 khugepaged_scan
.address
+= HPAGE_PMD_SIZE
;
2116 progress
+= HPAGE_PMD_NR
;
2118 /* we released mmap_sem so break loop */
2119 goto breakouterloop_mmap_sem
;
2120 if (progress
>= pages
)
2121 goto breakouterloop
;
2125 up_read(&mm
->mmap_sem
); /* exit_mmap will destroy ptes after this */
2126 breakouterloop_mmap_sem
:
2128 spin_lock(&khugepaged_mm_lock
);
2129 VM_BUG_ON(khugepaged_scan
.mm_slot
!= mm_slot
);
2131 * Release the current mm_slot if this mm is about to die, or
2132 * if we scanned all vmas of this mm.
2134 if (khugepaged_test_exit(mm
) || !vma
) {
2136 * Make sure that if mm_users is reaching zero while
2137 * khugepaged runs here, khugepaged_exit will find
2138 * mm_slot not pointing to the exiting mm.
2140 if (mm_slot
->mm_node
.next
!= &khugepaged_scan
.mm_head
) {
2141 khugepaged_scan
.mm_slot
= list_entry(
2142 mm_slot
->mm_node
.next
,
2143 struct mm_slot
, mm_node
);
2144 khugepaged_scan
.address
= 0;
2146 khugepaged_scan
.mm_slot
= NULL
;
2147 khugepaged_full_scans
++;
2150 collect_mm_slot(mm_slot
);
2156 static int khugepaged_has_work(void)
2158 return !list_empty(&khugepaged_scan
.mm_head
) &&
2159 khugepaged_enabled();
2162 static int khugepaged_wait_event(void)
2164 return !list_empty(&khugepaged_scan
.mm_head
) ||
2165 kthread_should_stop();
2168 static void khugepaged_do_scan(void)
2170 struct page
*hpage
= NULL
;
2171 unsigned int progress
= 0, pass_through_head
= 0;
2172 unsigned int pages
= khugepaged_pages_to_scan
;
2175 barrier(); /* write khugepaged_pages_to_scan to local stack */
2177 lru_add_drain_all();
2179 while (progress
< pages
) {
2180 if (!khugepaged_prealloc_page(&hpage
, &wait
))
2185 if (unlikely(kthread_should_stop() || try_to_freeze()))
2188 spin_lock(&khugepaged_mm_lock
);
2189 if (!khugepaged_scan
.mm_slot
)
2190 pass_through_head
++;
2191 if (khugepaged_has_work() &&
2192 pass_through_head
< 2)
2193 progress
+= khugepaged_scan_mm_slot(pages
- progress
,
2197 spin_unlock(&khugepaged_mm_lock
);
2200 if (!IS_ERR_OR_NULL(hpage
))
2204 static bool khugepaged_should_wakeup(void)
2206 return kthread_should_stop() ||
2207 time_after_eq(jiffies
, khugepaged_sleep_expire
);
2210 static void khugepaged_wait_work(void)
2212 if (khugepaged_has_work()) {
2213 const unsigned long scan_sleep_jiffies
=
2214 msecs_to_jiffies(khugepaged_scan_sleep_millisecs
);
2216 if (!scan_sleep_jiffies
)
2219 khugepaged_sleep_expire
= jiffies
+ scan_sleep_jiffies
;
2220 wait_event_freezable_timeout(khugepaged_wait
,
2221 khugepaged_should_wakeup(),
2222 scan_sleep_jiffies
);
2226 if (khugepaged_enabled())
2227 wait_event_freezable(khugepaged_wait
, khugepaged_wait_event());
2230 static int khugepaged(void *none
)
2232 struct mm_slot
*mm_slot
;
2235 set_user_nice(current
, MAX_NICE
);
2237 while (!kthread_should_stop()) {
2238 khugepaged_do_scan();
2239 khugepaged_wait_work();
2242 spin_lock(&khugepaged_mm_lock
);
2243 mm_slot
= khugepaged_scan
.mm_slot
;
2244 khugepaged_scan
.mm_slot
= NULL
;
2246 collect_mm_slot(mm_slot
);
2247 spin_unlock(&khugepaged_mm_lock
);
2251 static void set_recommended_min_free_kbytes(void)
2255 unsigned long recommended_min
;
2257 for_each_populated_zone(zone
) {
2259 * We don't need to worry about fragmentation of
2260 * ZONE_MOVABLE since it only has movable pages.
2262 if (zone_idx(zone
) > gfp_zone(GFP_USER
))
2268 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */
2269 recommended_min
= pageblock_nr_pages
* nr_zones
* 2;
2272 * Make sure that on average at least two pageblocks are almost free
2273 * of another type, one for a migratetype to fall back to and a
2274 * second to avoid subsequent fallbacks of other types There are 3
2275 * MIGRATE_TYPES we care about.
2277 recommended_min
+= pageblock_nr_pages
* nr_zones
*
2278 MIGRATE_PCPTYPES
* MIGRATE_PCPTYPES
;
2280 /* don't ever allow to reserve more than 5% of the lowmem */
2281 recommended_min
= min(recommended_min
,
2282 (unsigned long) nr_free_buffer_pages() / 20);
2283 recommended_min
<<= (PAGE_SHIFT
-10);
2285 if (recommended_min
> min_free_kbytes
) {
2286 if (user_min_free_kbytes
>= 0)
2287 pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n",
2288 min_free_kbytes
, recommended_min
);
2290 min_free_kbytes
= recommended_min
;
2292 setup_per_zone_wmarks();
2295 int start_stop_khugepaged(void)
2297 static struct task_struct
*khugepaged_thread __read_mostly
;
2298 static DEFINE_MUTEX(khugepaged_mutex
);
2301 mutex_lock(&khugepaged_mutex
);
2302 if (khugepaged_enabled()) {
2303 if (!khugepaged_thread
)
2304 khugepaged_thread
= kthread_run(khugepaged
, NULL
,
2306 if (IS_ERR(khugepaged_thread
)) {
2307 pr_err("khugepaged: kthread_run(khugepaged) failed\n");
2308 err
= PTR_ERR(khugepaged_thread
);
2309 khugepaged_thread
= NULL
;
2313 if (!list_empty(&khugepaged_scan
.mm_head
))
2314 wake_up_interruptible(&khugepaged_wait
);
2316 set_recommended_min_free_kbytes();
2317 } else if (khugepaged_thread
) {
2318 kthread_stop(khugepaged_thread
);
2319 khugepaged_thread
= NULL
;
2322 mutex_unlock(&khugepaged_mutex
);