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
93 * @nr_pte_mapped_thp: number of pte mapped THP
94 * @pte_mapped_thp: address array corresponding pte mapped THP
97 struct hlist_node hash
;
98 struct list_head mm_node
;
101 /* pte-mapped THP in this mm */
102 int nr_pte_mapped_thp
;
103 unsigned long pte_mapped_thp
[MAX_PTE_MAPPED_THP
];
107 * struct khugepaged_scan - cursor for scanning
108 * @mm_head: the head of the mm list to scan
109 * @mm_slot: the current mm_slot we are scanning
110 * @address: the next address inside that to be scanned
112 * There is only the one khugepaged_scan instance of this cursor structure.
114 struct khugepaged_scan
{
115 struct list_head mm_head
;
116 struct mm_slot
*mm_slot
;
117 unsigned long address
;
120 static struct khugepaged_scan khugepaged_scan
= {
121 .mm_head
= LIST_HEAD_INIT(khugepaged_scan
.mm_head
),
125 static ssize_t
scan_sleep_millisecs_show(struct kobject
*kobj
,
126 struct kobj_attribute
*attr
,
129 return sysfs_emit(buf
, "%u\n", khugepaged_scan_sleep_millisecs
);
132 static ssize_t
scan_sleep_millisecs_store(struct kobject
*kobj
,
133 struct kobj_attribute
*attr
,
134 const char *buf
, size_t count
)
139 err
= kstrtouint(buf
, 10, &msecs
);
143 khugepaged_scan_sleep_millisecs
= msecs
;
144 khugepaged_sleep_expire
= 0;
145 wake_up_interruptible(&khugepaged_wait
);
149 static struct kobj_attribute scan_sleep_millisecs_attr
=
150 __ATTR(scan_sleep_millisecs
, 0644, scan_sleep_millisecs_show
,
151 scan_sleep_millisecs_store
);
153 static ssize_t
alloc_sleep_millisecs_show(struct kobject
*kobj
,
154 struct kobj_attribute
*attr
,
157 return sysfs_emit(buf
, "%u\n", khugepaged_alloc_sleep_millisecs
);
160 static ssize_t
alloc_sleep_millisecs_store(struct kobject
*kobj
,
161 struct kobj_attribute
*attr
,
162 const char *buf
, size_t count
)
167 err
= kstrtouint(buf
, 10, &msecs
);
171 khugepaged_alloc_sleep_millisecs
= msecs
;
172 khugepaged_sleep_expire
= 0;
173 wake_up_interruptible(&khugepaged_wait
);
177 static struct kobj_attribute alloc_sleep_millisecs_attr
=
178 __ATTR(alloc_sleep_millisecs
, 0644, alloc_sleep_millisecs_show
,
179 alloc_sleep_millisecs_store
);
181 static ssize_t
pages_to_scan_show(struct kobject
*kobj
,
182 struct kobj_attribute
*attr
,
185 return sysfs_emit(buf
, "%u\n", khugepaged_pages_to_scan
);
187 static ssize_t
pages_to_scan_store(struct kobject
*kobj
,
188 struct kobj_attribute
*attr
,
189 const char *buf
, size_t count
)
194 err
= kstrtouint(buf
, 10, &pages
);
198 khugepaged_pages_to_scan
= pages
;
202 static struct kobj_attribute pages_to_scan_attr
=
203 __ATTR(pages_to_scan
, 0644, pages_to_scan_show
,
204 pages_to_scan_store
);
206 static ssize_t
pages_collapsed_show(struct kobject
*kobj
,
207 struct kobj_attribute
*attr
,
210 return sysfs_emit(buf
, "%u\n", khugepaged_pages_collapsed
);
212 static struct kobj_attribute pages_collapsed_attr
=
213 __ATTR_RO(pages_collapsed
);
215 static ssize_t
full_scans_show(struct kobject
*kobj
,
216 struct kobj_attribute
*attr
,
219 return sysfs_emit(buf
, "%u\n", khugepaged_full_scans
);
221 static struct kobj_attribute full_scans_attr
=
222 __ATTR_RO(full_scans
);
224 static ssize_t
khugepaged_defrag_show(struct kobject
*kobj
,
225 struct kobj_attribute
*attr
, char *buf
)
227 return single_hugepage_flag_show(kobj
, attr
, buf
,
228 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG
);
230 static ssize_t
khugepaged_defrag_store(struct kobject
*kobj
,
231 struct kobj_attribute
*attr
,
232 const char *buf
, size_t count
)
234 return single_hugepage_flag_store(kobj
, attr
, buf
, count
,
235 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG
);
237 static struct kobj_attribute khugepaged_defrag_attr
=
238 __ATTR(defrag
, 0644, khugepaged_defrag_show
,
239 khugepaged_defrag_store
);
242 * max_ptes_none controls if khugepaged should collapse hugepages over
243 * any unmapped ptes in turn potentially increasing the memory
244 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
245 * reduce the available free memory in the system as it
246 * runs. Increasing max_ptes_none will instead potentially reduce the
247 * free memory in the system during the khugepaged scan.
249 static ssize_t
khugepaged_max_ptes_none_show(struct kobject
*kobj
,
250 struct kobj_attribute
*attr
,
253 return sysfs_emit(buf
, "%u\n", khugepaged_max_ptes_none
);
255 static ssize_t
khugepaged_max_ptes_none_store(struct kobject
*kobj
,
256 struct kobj_attribute
*attr
,
257 const char *buf
, size_t count
)
260 unsigned long max_ptes_none
;
262 err
= kstrtoul(buf
, 10, &max_ptes_none
);
263 if (err
|| max_ptes_none
> HPAGE_PMD_NR
-1)
266 khugepaged_max_ptes_none
= max_ptes_none
;
270 static struct kobj_attribute khugepaged_max_ptes_none_attr
=
271 __ATTR(max_ptes_none
, 0644, khugepaged_max_ptes_none_show
,
272 khugepaged_max_ptes_none_store
);
274 static ssize_t
khugepaged_max_ptes_swap_show(struct kobject
*kobj
,
275 struct kobj_attribute
*attr
,
278 return sysfs_emit(buf
, "%u\n", khugepaged_max_ptes_swap
);
281 static ssize_t
khugepaged_max_ptes_swap_store(struct kobject
*kobj
,
282 struct kobj_attribute
*attr
,
283 const char *buf
, size_t count
)
286 unsigned long max_ptes_swap
;
288 err
= kstrtoul(buf
, 10, &max_ptes_swap
);
289 if (err
|| max_ptes_swap
> HPAGE_PMD_NR
-1)
292 khugepaged_max_ptes_swap
= max_ptes_swap
;
297 static struct kobj_attribute khugepaged_max_ptes_swap_attr
=
298 __ATTR(max_ptes_swap
, 0644, khugepaged_max_ptes_swap_show
,
299 khugepaged_max_ptes_swap_store
);
301 static ssize_t
khugepaged_max_ptes_shared_show(struct kobject
*kobj
,
302 struct kobj_attribute
*attr
,
305 return sysfs_emit(buf
, "%u\n", khugepaged_max_ptes_shared
);
308 static ssize_t
khugepaged_max_ptes_shared_store(struct kobject
*kobj
,
309 struct kobj_attribute
*attr
,
310 const char *buf
, size_t count
)
313 unsigned long max_ptes_shared
;
315 err
= kstrtoul(buf
, 10, &max_ptes_shared
);
316 if (err
|| max_ptes_shared
> HPAGE_PMD_NR
-1)
319 khugepaged_max_ptes_shared
= max_ptes_shared
;
324 static struct kobj_attribute khugepaged_max_ptes_shared_attr
=
325 __ATTR(max_ptes_shared
, 0644, khugepaged_max_ptes_shared_show
,
326 khugepaged_max_ptes_shared_store
);
328 static struct attribute
*khugepaged_attr
[] = {
329 &khugepaged_defrag_attr
.attr
,
330 &khugepaged_max_ptes_none_attr
.attr
,
331 &khugepaged_max_ptes_swap_attr
.attr
,
332 &khugepaged_max_ptes_shared_attr
.attr
,
333 &pages_to_scan_attr
.attr
,
334 &pages_collapsed_attr
.attr
,
335 &full_scans_attr
.attr
,
336 &scan_sleep_millisecs_attr
.attr
,
337 &alloc_sleep_millisecs_attr
.attr
,
341 struct attribute_group khugepaged_attr_group
= {
342 .attrs
= khugepaged_attr
,
343 .name
= "khugepaged",
345 #endif /* CONFIG_SYSFS */
347 int hugepage_madvise(struct vm_area_struct
*vma
,
348 unsigned long *vm_flags
, int advice
)
354 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
355 * can't handle this properly after s390_enable_sie, so we simply
356 * ignore the madvise to prevent qemu from causing a SIGSEGV.
358 if (mm_has_pgste(vma
->vm_mm
))
361 *vm_flags
&= ~VM_NOHUGEPAGE
;
362 *vm_flags
|= VM_HUGEPAGE
;
364 * If the vma become good for khugepaged to scan,
365 * register it here without waiting a page fault that
366 * may not happen any time soon.
368 if (!(*vm_flags
& VM_NO_KHUGEPAGED
) &&
369 khugepaged_enter_vma_merge(vma
, *vm_flags
))
372 case MADV_NOHUGEPAGE
:
373 *vm_flags
&= ~VM_HUGEPAGE
;
374 *vm_flags
|= VM_NOHUGEPAGE
;
376 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
377 * this vma even if we leave the mm registered in khugepaged if
378 * it got registered before VM_NOHUGEPAGE was set.
386 int __init
khugepaged_init(void)
388 mm_slot_cache
= kmem_cache_create("khugepaged_mm_slot",
389 sizeof(struct mm_slot
),
390 __alignof__(struct mm_slot
), 0, NULL
);
394 khugepaged_pages_to_scan
= HPAGE_PMD_NR
* 8;
395 khugepaged_max_ptes_none
= HPAGE_PMD_NR
- 1;
396 khugepaged_max_ptes_swap
= HPAGE_PMD_NR
/ 8;
397 khugepaged_max_ptes_shared
= HPAGE_PMD_NR
/ 2;
402 void __init
khugepaged_destroy(void)
404 kmem_cache_destroy(mm_slot_cache
);
407 static inline struct mm_slot
*alloc_mm_slot(void)
409 if (!mm_slot_cache
) /* initialization failed */
411 return kmem_cache_zalloc(mm_slot_cache
, GFP_KERNEL
);
414 static inline void free_mm_slot(struct mm_slot
*mm_slot
)
416 kmem_cache_free(mm_slot_cache
, mm_slot
);
419 static struct mm_slot
*get_mm_slot(struct mm_struct
*mm
)
421 struct mm_slot
*mm_slot
;
423 hash_for_each_possible(mm_slots_hash
, mm_slot
, hash
, (unsigned long)mm
)
424 if (mm
== mm_slot
->mm
)
430 static void insert_to_mm_slots_hash(struct mm_struct
*mm
,
431 struct mm_slot
*mm_slot
)
434 hash_add(mm_slots_hash
, &mm_slot
->hash
, (long)mm
);
437 static inline int khugepaged_test_exit(struct mm_struct
*mm
)
439 return atomic_read(&mm
->mm_users
) == 0;
442 static bool hugepage_vma_check(struct vm_area_struct
*vma
,
443 unsigned long vm_flags
)
445 if (!transhuge_vma_enabled(vma
, vm_flags
))
448 /* Enabled via shmem mount options or sysfs settings. */
449 if (shmem_file(vma
->vm_file
) && shmem_huge_enabled(vma
)) {
450 return IS_ALIGNED((vma
->vm_start
>> PAGE_SHIFT
) - vma
->vm_pgoff
,
454 /* THP settings require madvise. */
455 if (!(vm_flags
& VM_HUGEPAGE
) && !khugepaged_always())
458 /* Read-only file mappings need to be aligned for THP to work. */
459 if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS
) && vma
->vm_file
&&
460 !inode_is_open_for_write(vma
->vm_file
->f_inode
) &&
461 (vm_flags
& VM_EXEC
)) {
462 return IS_ALIGNED((vma
->vm_start
>> PAGE_SHIFT
) - vma
->vm_pgoff
,
466 if (!vma
->anon_vma
|| vma
->vm_ops
)
468 if (vma_is_temporary_stack(vma
))
470 return !(vm_flags
& VM_NO_KHUGEPAGED
);
473 int __khugepaged_enter(struct mm_struct
*mm
)
475 struct mm_slot
*mm_slot
;
478 mm_slot
= alloc_mm_slot();
482 /* __khugepaged_exit() must not run from under us */
483 VM_BUG_ON_MM(khugepaged_test_exit(mm
), mm
);
484 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE
, &mm
->flags
))) {
485 free_mm_slot(mm_slot
);
489 spin_lock(&khugepaged_mm_lock
);
490 insert_to_mm_slots_hash(mm
, mm_slot
);
492 * Insert just behind the scanning cursor, to let the area settle
495 wakeup
= list_empty(&khugepaged_scan
.mm_head
);
496 list_add_tail(&mm_slot
->mm_node
, &khugepaged_scan
.mm_head
);
497 spin_unlock(&khugepaged_mm_lock
);
501 wake_up_interruptible(&khugepaged_wait
);
506 int khugepaged_enter_vma_merge(struct vm_area_struct
*vma
,
507 unsigned long vm_flags
)
509 unsigned long hstart
, hend
;
512 * khugepaged only supports read-only files for non-shmem files.
513 * khugepaged does not yet work on special mappings. And
514 * file-private shmem THP is not supported.
516 if (!hugepage_vma_check(vma
, vm_flags
))
519 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
520 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
522 return khugepaged_enter(vma
, vm_flags
);
526 void __khugepaged_exit(struct mm_struct
*mm
)
528 struct mm_slot
*mm_slot
;
531 spin_lock(&khugepaged_mm_lock
);
532 mm_slot
= get_mm_slot(mm
);
533 if (mm_slot
&& khugepaged_scan
.mm_slot
!= mm_slot
) {
534 hash_del(&mm_slot
->hash
);
535 list_del(&mm_slot
->mm_node
);
538 spin_unlock(&khugepaged_mm_lock
);
541 clear_bit(MMF_VM_HUGEPAGE
, &mm
->flags
);
542 free_mm_slot(mm_slot
);
544 } else if (mm_slot
) {
546 * This is required to serialize against
547 * khugepaged_test_exit() (which is guaranteed to run
548 * under mmap sem read mode). Stop here (after we
549 * return all pagetables will be destroyed) until
550 * khugepaged has finished working on the pagetables
551 * under the mmap_lock.
554 mmap_write_unlock(mm
);
558 static void release_pte_page(struct page
*page
)
560 mod_node_page_state(page_pgdat(page
),
561 NR_ISOLATED_ANON
+ page_is_file_lru(page
),
564 putback_lru_page(page
);
567 static void release_pte_pages(pte_t
*pte
, pte_t
*_pte
,
568 struct list_head
*compound_pagelist
)
570 struct page
*page
, *tmp
;
572 while (--_pte
>= pte
) {
573 pte_t pteval
= *_pte
;
575 page
= pte_page(pteval
);
576 if (!pte_none(pteval
) && !is_zero_pfn(pte_pfn(pteval
)) &&
578 release_pte_page(page
);
581 list_for_each_entry_safe(page
, tmp
, compound_pagelist
, lru
) {
582 list_del(&page
->lru
);
583 release_pte_page(page
);
587 static bool is_refcount_suitable(struct page
*page
)
589 int expected_refcount
;
591 expected_refcount
= total_mapcount(page
);
592 if (PageSwapCache(page
))
593 expected_refcount
+= compound_nr(page
);
595 return page_count(page
) == expected_refcount
;
598 static int __collapse_huge_page_isolate(struct vm_area_struct
*vma
,
599 unsigned long address
,
601 struct list_head
*compound_pagelist
)
603 struct page
*page
= NULL
;
605 int none_or_zero
= 0, shared
= 0, result
= 0, referenced
= 0;
606 bool writable
= false;
608 for (_pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
;
609 _pte
++, address
+= PAGE_SIZE
) {
610 pte_t pteval
= *_pte
;
611 if (pte_none(pteval
) || (pte_present(pteval
) &&
612 is_zero_pfn(pte_pfn(pteval
)))) {
613 if (!userfaultfd_armed(vma
) &&
614 ++none_or_zero
<= khugepaged_max_ptes_none
) {
617 result
= SCAN_EXCEED_NONE_PTE
;
621 if (!pte_present(pteval
)) {
622 result
= SCAN_PTE_NON_PRESENT
;
625 page
= vm_normal_page(vma
, address
, pteval
);
626 if (unlikely(!page
)) {
627 result
= SCAN_PAGE_NULL
;
631 VM_BUG_ON_PAGE(!PageAnon(page
), page
);
633 if (page_mapcount(page
) > 1 &&
634 ++shared
> khugepaged_max_ptes_shared
) {
635 result
= SCAN_EXCEED_SHARED_PTE
;
639 if (PageCompound(page
)) {
641 page
= compound_head(page
);
644 * Check if we have dealt with the compound page
647 list_for_each_entry(p
, compound_pagelist
, lru
) {
654 * We can do it before isolate_lru_page because the
655 * page can't be freed from under us. NOTE: PG_lock
656 * is needed to serialize against split_huge_page
657 * when invoked from the VM.
659 if (!trylock_page(page
)) {
660 result
= SCAN_PAGE_LOCK
;
665 * Check if the page has any GUP (or other external) pins.
667 * The page table that maps the page has been already unlinked
668 * from the page table tree and this process cannot get
669 * an additional pin on the page.
671 * New pins can come later if the page is shared across fork,
672 * but not from this process. The other process cannot write to
673 * the page, only trigger CoW.
675 if (!is_refcount_suitable(page
)) {
677 result
= SCAN_PAGE_COUNT
;
680 if (!pte_write(pteval
) && PageSwapCache(page
) &&
681 !reuse_swap_page(page
, NULL
)) {
683 * Page is in the swap cache and cannot be re-used.
684 * It cannot be collapsed into a THP.
687 result
= SCAN_SWAP_CACHE_PAGE
;
692 * Isolate the page to avoid collapsing an hugepage
693 * currently in use by the VM.
695 if (isolate_lru_page(page
)) {
697 result
= SCAN_DEL_PAGE_LRU
;
700 mod_node_page_state(page_pgdat(page
),
701 NR_ISOLATED_ANON
+ page_is_file_lru(page
),
703 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
704 VM_BUG_ON_PAGE(PageLRU(page
), page
);
706 if (PageCompound(page
))
707 list_add_tail(&page
->lru
, compound_pagelist
);
709 /* There should be enough young pte to collapse the page */
710 if (pte_young(pteval
) ||
711 page_is_young(page
) || PageReferenced(page
) ||
712 mmu_notifier_test_young(vma
->vm_mm
, address
))
715 if (pte_write(pteval
))
719 if (unlikely(!writable
)) {
720 result
= SCAN_PAGE_RO
;
721 } else if (unlikely(!referenced
)) {
722 result
= SCAN_LACK_REFERENCED_PAGE
;
724 result
= SCAN_SUCCEED
;
725 trace_mm_collapse_huge_page_isolate(page
, none_or_zero
,
726 referenced
, writable
, result
);
730 release_pte_pages(pte
, _pte
, compound_pagelist
);
731 trace_mm_collapse_huge_page_isolate(page
, none_or_zero
,
732 referenced
, writable
, result
);
736 static void __collapse_huge_page_copy(pte_t
*pte
, struct page
*page
,
737 struct vm_area_struct
*vma
,
738 unsigned long address
,
740 struct list_head
*compound_pagelist
)
742 struct page
*src_page
, *tmp
;
744 for (_pte
= pte
; _pte
< pte
+ HPAGE_PMD_NR
;
745 _pte
++, page
++, address
+= PAGE_SIZE
) {
746 pte_t pteval
= *_pte
;
748 if (pte_none(pteval
) || is_zero_pfn(pte_pfn(pteval
))) {
749 clear_user_highpage(page
, address
);
750 add_mm_counter(vma
->vm_mm
, MM_ANONPAGES
, 1);
751 if (is_zero_pfn(pte_pfn(pteval
))) {
753 * ptl mostly unnecessary.
757 * paravirt calls inside pte_clear here are
760 pte_clear(vma
->vm_mm
, address
, _pte
);
764 src_page
= pte_page(pteval
);
765 copy_user_highpage(page
, src_page
, address
, vma
);
766 if (!PageCompound(src_page
))
767 release_pte_page(src_page
);
769 * ptl mostly unnecessary, but preempt has to
770 * be disabled to update the per-cpu stats
771 * inside page_remove_rmap().
775 * paravirt calls inside pte_clear here are
778 pte_clear(vma
->vm_mm
, address
, _pte
);
779 page_remove_rmap(src_page
, false);
781 free_page_and_swap_cache(src_page
);
785 list_for_each_entry_safe(src_page
, tmp
, compound_pagelist
, lru
) {
786 list_del(&src_page
->lru
);
787 release_pte_page(src_page
);
791 static void khugepaged_alloc_sleep(void)
795 add_wait_queue(&khugepaged_wait
, &wait
);
796 freezable_schedule_timeout_interruptible(
797 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs
));
798 remove_wait_queue(&khugepaged_wait
, &wait
);
801 static int khugepaged_node_load
[MAX_NUMNODES
];
803 static bool khugepaged_scan_abort(int nid
)
808 * If node_reclaim_mode is disabled, then no extra effort is made to
809 * allocate memory locally.
811 if (!node_reclaim_enabled())
814 /* If there is a count for this node already, it must be acceptable */
815 if (khugepaged_node_load
[nid
])
818 for (i
= 0; i
< MAX_NUMNODES
; i
++) {
819 if (!khugepaged_node_load
[i
])
821 if (node_distance(nid
, i
) > node_reclaim_distance
)
827 /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */
828 static inline gfp_t
alloc_hugepage_khugepaged_gfpmask(void)
830 return khugepaged_defrag() ? GFP_TRANSHUGE
: GFP_TRANSHUGE_LIGHT
;
834 static int khugepaged_find_target_node(void)
836 static int last_khugepaged_target_node
= NUMA_NO_NODE
;
837 int nid
, target_node
= 0, max_value
= 0;
839 /* find first node with max normal pages hit */
840 for (nid
= 0; nid
< MAX_NUMNODES
; nid
++)
841 if (khugepaged_node_load
[nid
] > max_value
) {
842 max_value
= khugepaged_node_load
[nid
];
846 /* do some balance if several nodes have the same hit record */
847 if (target_node
<= last_khugepaged_target_node
)
848 for (nid
= last_khugepaged_target_node
+ 1; nid
< MAX_NUMNODES
;
850 if (max_value
== khugepaged_node_load
[nid
]) {
855 last_khugepaged_target_node
= target_node
;
859 static bool khugepaged_prealloc_page(struct page
**hpage
, bool *wait
)
861 if (IS_ERR(*hpage
)) {
867 khugepaged_alloc_sleep();
877 khugepaged_alloc_page(struct page
**hpage
, gfp_t gfp
, int node
)
879 VM_BUG_ON_PAGE(*hpage
, *hpage
);
881 *hpage
= __alloc_pages_node(node
, gfp
, HPAGE_PMD_ORDER
);
882 if (unlikely(!*hpage
)) {
883 count_vm_event(THP_COLLAPSE_ALLOC_FAILED
);
884 *hpage
= ERR_PTR(-ENOMEM
);
888 prep_transhuge_page(*hpage
);
889 count_vm_event(THP_COLLAPSE_ALLOC
);
893 static int khugepaged_find_target_node(void)
898 static inline struct page
*alloc_khugepaged_hugepage(void)
902 page
= alloc_pages(alloc_hugepage_khugepaged_gfpmask(),
905 prep_transhuge_page(page
);
909 static struct page
*khugepaged_alloc_hugepage(bool *wait
)
914 hpage
= alloc_khugepaged_hugepage();
916 count_vm_event(THP_COLLAPSE_ALLOC_FAILED
);
921 khugepaged_alloc_sleep();
923 count_vm_event(THP_COLLAPSE_ALLOC
);
924 } while (unlikely(!hpage
) && likely(khugepaged_enabled()));
929 static bool khugepaged_prealloc_page(struct page
**hpage
, bool *wait
)
932 * If the hpage allocated earlier was briefly exposed in page cache
933 * before collapse_file() failed, it is possible that racing lookups
934 * have not yet completed, and would then be unpleasantly surprised by
935 * finding the hpage reused for the same mapping at a different offset.
936 * Just release the previous allocation if there is any danger of that.
938 if (*hpage
&& page_count(*hpage
) > 1) {
944 *hpage
= khugepaged_alloc_hugepage(wait
);
946 if (unlikely(!*hpage
))
953 khugepaged_alloc_page(struct page
**hpage
, gfp_t gfp
, int node
)
962 * If mmap_lock temporarily dropped, revalidate vma
963 * before taking mmap_lock.
964 * Return 0 if succeeds, otherwise return none-zero
968 static int hugepage_vma_revalidate(struct mm_struct
*mm
, unsigned long address
,
969 struct vm_area_struct
**vmap
)
971 struct vm_area_struct
*vma
;
972 unsigned long hstart
, hend
;
974 if (unlikely(khugepaged_test_exit(mm
)))
975 return SCAN_ANY_PROCESS
;
977 *vmap
= vma
= find_vma(mm
, address
);
979 return SCAN_VMA_NULL
;
981 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
982 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
983 if (address
< hstart
|| address
+ HPAGE_PMD_SIZE
> hend
)
984 return SCAN_ADDRESS_RANGE
;
985 if (!hugepage_vma_check(vma
, vma
->vm_flags
))
986 return SCAN_VMA_CHECK
;
987 /* Anon VMA expected */
988 if (!vma
->anon_vma
|| vma
->vm_ops
)
989 return SCAN_VMA_CHECK
;
994 * Bring missing pages in from swap, to complete THP collapse.
995 * Only done if khugepaged_scan_pmd believes it is worthwhile.
997 * Called and returns without pte mapped or spinlocks held,
998 * but with mmap_lock held to protect against vma changes.
1001 static bool __collapse_huge_page_swapin(struct mm_struct
*mm
,
1002 struct vm_area_struct
*vma
,
1003 unsigned long haddr
, pmd_t
*pmd
,
1008 unsigned long address
, end
= haddr
+ (HPAGE_PMD_NR
* PAGE_SIZE
);
1010 for (address
= haddr
; address
< end
; address
+= PAGE_SIZE
) {
1011 struct vm_fault vmf
= {
1014 .pgoff
= linear_page_index(vma
, haddr
),
1015 .flags
= FAULT_FLAG_ALLOW_RETRY
,
1019 vmf
.pte
= pte_offset_map(pmd
, address
);
1020 vmf
.orig_pte
= *vmf
.pte
;
1021 if (!is_swap_pte(vmf
.orig_pte
)) {
1026 ret
= do_swap_page(&vmf
);
1028 /* do_swap_page returns VM_FAULT_RETRY with released mmap_lock */
1029 if (ret
& VM_FAULT_RETRY
) {
1031 if (hugepage_vma_revalidate(mm
, haddr
, &vma
)) {
1032 /* vma is no longer available, don't continue to swapin */
1033 trace_mm_collapse_huge_page_swapin(mm
, swapped_in
, referenced
, 0);
1036 /* check if the pmd is still valid */
1037 if (mm_find_pmd(mm
, haddr
) != pmd
) {
1038 trace_mm_collapse_huge_page_swapin(mm
, swapped_in
, referenced
, 0);
1042 if (ret
& VM_FAULT_ERROR
) {
1043 trace_mm_collapse_huge_page_swapin(mm
, swapped_in
, referenced
, 0);
1048 /* Drain LRU add pagevec to remove extra pin on the swapped in pages */
1052 trace_mm_collapse_huge_page_swapin(mm
, swapped_in
, referenced
, 1);
1056 static void collapse_huge_page(struct mm_struct
*mm
,
1057 unsigned long address
,
1058 struct page
**hpage
,
1059 int node
, int referenced
, int unmapped
)
1061 LIST_HEAD(compound_pagelist
);
1065 struct page
*new_page
;
1066 spinlock_t
*pmd_ptl
, *pte_ptl
;
1067 int isolated
= 0, result
= 0;
1068 struct vm_area_struct
*vma
;
1069 struct mmu_notifier_range range
;
1072 VM_BUG_ON(address
& ~HPAGE_PMD_MASK
);
1074 /* Only allocate from the target node */
1075 gfp
= alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE
;
1078 * Before allocating the hugepage, release the mmap_lock read lock.
1079 * The allocation can take potentially a long time if it involves
1080 * sync compaction, and we do not need to hold the mmap_lock during
1081 * that. We will recheck the vma after taking it again in write mode.
1083 mmap_read_unlock(mm
);
1084 new_page
= khugepaged_alloc_page(hpage
, gfp
, node
);
1086 result
= SCAN_ALLOC_HUGE_PAGE_FAIL
;
1090 if (unlikely(mem_cgroup_charge(new_page
, mm
, gfp
))) {
1091 result
= SCAN_CGROUP_CHARGE_FAIL
;
1094 count_memcg_page_event(new_page
, THP_COLLAPSE_ALLOC
);
1097 result
= hugepage_vma_revalidate(mm
, address
, &vma
);
1099 mmap_read_unlock(mm
);
1103 pmd
= mm_find_pmd(mm
, address
);
1105 result
= SCAN_PMD_NULL
;
1106 mmap_read_unlock(mm
);
1111 * __collapse_huge_page_swapin always returns with mmap_lock locked.
1112 * If it fails, we release mmap_lock and jump out_nolock.
1113 * Continuing to collapse causes inconsistency.
1115 if (unmapped
&& !__collapse_huge_page_swapin(mm
, vma
, address
,
1117 mmap_read_unlock(mm
);
1121 mmap_read_unlock(mm
);
1123 * Prevent all access to pagetables with the exception of
1124 * gup_fast later handled by the ptep_clear_flush and the VM
1125 * handled by the anon_vma lock + PG_lock.
1127 mmap_write_lock(mm
);
1128 result
= hugepage_vma_revalidate(mm
, address
, &vma
);
1131 /* check if the pmd is still valid */
1132 if (mm_find_pmd(mm
, address
) != pmd
)
1135 anon_vma_lock_write(vma
->anon_vma
);
1137 mmu_notifier_range_init(&range
, MMU_NOTIFY_CLEAR
, 0, NULL
, mm
,
1138 address
, address
+ HPAGE_PMD_SIZE
);
1139 mmu_notifier_invalidate_range_start(&range
);
1141 pte
= pte_offset_map(pmd
, address
);
1142 pte_ptl
= pte_lockptr(mm
, pmd
);
1144 pmd_ptl
= pmd_lock(mm
, pmd
); /* probably unnecessary */
1146 * After this gup_fast can't run anymore. This also removes
1147 * any huge TLB entry from the CPU so we won't allow
1148 * huge and small TLB entries for the same virtual address
1149 * to avoid the risk of CPU bugs in that area.
1151 _pmd
= pmdp_collapse_flush(vma
, address
, pmd
);
1152 spin_unlock(pmd_ptl
);
1153 mmu_notifier_invalidate_range_end(&range
);
1156 isolated
= __collapse_huge_page_isolate(vma
, address
, pte
,
1157 &compound_pagelist
);
1158 spin_unlock(pte_ptl
);
1160 if (unlikely(!isolated
)) {
1163 BUG_ON(!pmd_none(*pmd
));
1165 * We can only use set_pmd_at when establishing
1166 * hugepmds and never for establishing regular pmds that
1167 * points to regular pagetables. Use pmd_populate for that
1169 pmd_populate(mm
, pmd
, pmd_pgtable(_pmd
));
1170 spin_unlock(pmd_ptl
);
1171 anon_vma_unlock_write(vma
->anon_vma
);
1177 * All pages are isolated and locked so anon_vma rmap
1178 * can't run anymore.
1180 anon_vma_unlock_write(vma
->anon_vma
);
1182 __collapse_huge_page_copy(pte
, new_page
, vma
, address
, pte_ptl
,
1183 &compound_pagelist
);
1186 * spin_lock() below is not the equivalent of smp_wmb(), but
1187 * the smp_wmb() inside __SetPageUptodate() can be reused to
1188 * avoid the copy_huge_page writes to become visible after
1189 * the set_pmd_at() write.
1191 __SetPageUptodate(new_page
);
1192 pgtable
= pmd_pgtable(_pmd
);
1194 _pmd
= mk_huge_pmd(new_page
, vma
->vm_page_prot
);
1195 _pmd
= maybe_pmd_mkwrite(pmd_mkdirty(_pmd
), vma
);
1198 BUG_ON(!pmd_none(*pmd
));
1199 page_add_new_anon_rmap(new_page
, vma
, address
, true);
1200 lru_cache_add_inactive_or_unevictable(new_page
, vma
);
1201 pgtable_trans_huge_deposit(mm
, pmd
, pgtable
);
1202 set_pmd_at(mm
, address
, pmd
, _pmd
);
1203 update_mmu_cache_pmd(vma
, address
, pmd
);
1204 spin_unlock(pmd_ptl
);
1208 khugepaged_pages_collapsed
++;
1209 result
= SCAN_SUCCEED
;
1211 mmap_write_unlock(mm
);
1213 if (!IS_ERR_OR_NULL(*hpage
))
1214 mem_cgroup_uncharge(*hpage
);
1215 trace_mm_collapse_huge_page(mm
, isolated
, result
);
1219 static int khugepaged_scan_pmd(struct mm_struct
*mm
,
1220 struct vm_area_struct
*vma
,
1221 unsigned long address
,
1222 struct page
**hpage
)
1226 int ret
= 0, result
= 0, referenced
= 0;
1227 int none_or_zero
= 0, shared
= 0;
1228 struct page
*page
= NULL
;
1229 unsigned long _address
;
1231 int node
= NUMA_NO_NODE
, unmapped
= 0;
1232 bool writable
= false;
1234 VM_BUG_ON(address
& ~HPAGE_PMD_MASK
);
1236 pmd
= mm_find_pmd(mm
, address
);
1238 result
= SCAN_PMD_NULL
;
1242 memset(khugepaged_node_load
, 0, sizeof(khugepaged_node_load
));
1243 pte
= pte_offset_map_lock(mm
, pmd
, address
, &ptl
);
1244 for (_address
= address
, _pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
;
1245 _pte
++, _address
+= PAGE_SIZE
) {
1246 pte_t pteval
= *_pte
;
1247 if (is_swap_pte(pteval
)) {
1248 if (++unmapped
<= khugepaged_max_ptes_swap
) {
1250 * Always be strict with uffd-wp
1251 * enabled swap entries. Please see
1252 * comment below for pte_uffd_wp().
1254 if (pte_swp_uffd_wp(pteval
)) {
1255 result
= SCAN_PTE_UFFD_WP
;
1260 result
= SCAN_EXCEED_SWAP_PTE
;
1264 if (pte_none(pteval
) || is_zero_pfn(pte_pfn(pteval
))) {
1265 if (!userfaultfd_armed(vma
) &&
1266 ++none_or_zero
<= khugepaged_max_ptes_none
) {
1269 result
= SCAN_EXCEED_NONE_PTE
;
1273 if (pte_uffd_wp(pteval
)) {
1275 * Don't collapse the page if any of the small
1276 * PTEs are armed with uffd write protection.
1277 * Here we can also mark the new huge pmd as
1278 * write protected if any of the small ones is
1279 * marked but that could bring unknown
1280 * userfault messages that falls outside of
1281 * the registered range. So, just be simple.
1283 result
= SCAN_PTE_UFFD_WP
;
1286 if (pte_write(pteval
))
1289 page
= vm_normal_page(vma
, _address
, pteval
);
1290 if (unlikely(!page
)) {
1291 result
= SCAN_PAGE_NULL
;
1295 if (page_mapcount(page
) > 1 &&
1296 ++shared
> khugepaged_max_ptes_shared
) {
1297 result
= SCAN_EXCEED_SHARED_PTE
;
1301 page
= compound_head(page
);
1304 * Record which node the original page is from and save this
1305 * information to khugepaged_node_load[].
1306 * Khupaged will allocate hugepage from the node has the max
1309 node
= page_to_nid(page
);
1310 if (khugepaged_scan_abort(node
)) {
1311 result
= SCAN_SCAN_ABORT
;
1314 khugepaged_node_load
[node
]++;
1315 if (!PageLRU(page
)) {
1316 result
= SCAN_PAGE_LRU
;
1319 if (PageLocked(page
)) {
1320 result
= SCAN_PAGE_LOCK
;
1323 if (!PageAnon(page
)) {
1324 result
= SCAN_PAGE_ANON
;
1329 * Check if the page has any GUP (or other external) pins.
1331 * Here the check is racy it may see totmal_mapcount > refcount
1333 * For example, one process with one forked child process.
1334 * The parent has the PMD split due to MADV_DONTNEED, then
1335 * the child is trying unmap the whole PMD, but khugepaged
1336 * may be scanning the parent between the child has
1337 * PageDoubleMap flag cleared and dec the mapcount. So
1338 * khugepaged may see total_mapcount > refcount.
1340 * But such case is ephemeral we could always retry collapse
1341 * later. However it may report false positive if the page
1342 * has excessive GUP pins (i.e. 512). Anyway the same check
1343 * will be done again later the risk seems low.
1345 if (!is_refcount_suitable(page
)) {
1346 result
= SCAN_PAGE_COUNT
;
1349 if (pte_young(pteval
) ||
1350 page_is_young(page
) || PageReferenced(page
) ||
1351 mmu_notifier_test_young(vma
->vm_mm
, address
))
1355 result
= SCAN_PAGE_RO
;
1356 } else if (!referenced
|| (unmapped
&& referenced
< HPAGE_PMD_NR
/2)) {
1357 result
= SCAN_LACK_REFERENCED_PAGE
;
1359 result
= SCAN_SUCCEED
;
1363 pte_unmap_unlock(pte
, ptl
);
1365 node
= khugepaged_find_target_node();
1366 /* collapse_huge_page will return with the mmap_lock released */
1367 collapse_huge_page(mm
, address
, hpage
, node
,
1368 referenced
, unmapped
);
1371 trace_mm_khugepaged_scan_pmd(mm
, page
, writable
, referenced
,
1372 none_or_zero
, result
, unmapped
);
1376 static void collect_mm_slot(struct mm_slot
*mm_slot
)
1378 struct mm_struct
*mm
= mm_slot
->mm
;
1380 lockdep_assert_held(&khugepaged_mm_lock
);
1382 if (khugepaged_test_exit(mm
)) {
1384 hash_del(&mm_slot
->hash
);
1385 list_del(&mm_slot
->mm_node
);
1388 * Not strictly needed because the mm exited already.
1390 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1393 /* khugepaged_mm_lock actually not necessary for the below */
1394 free_mm_slot(mm_slot
);
1401 * Notify khugepaged that given addr of the mm is pte-mapped THP. Then
1402 * khugepaged should try to collapse the page table.
1404 static int khugepaged_add_pte_mapped_thp(struct mm_struct
*mm
,
1407 struct mm_slot
*mm_slot
;
1409 VM_BUG_ON(addr
& ~HPAGE_PMD_MASK
);
1411 spin_lock(&khugepaged_mm_lock
);
1412 mm_slot
= get_mm_slot(mm
);
1413 if (likely(mm_slot
&& mm_slot
->nr_pte_mapped_thp
< MAX_PTE_MAPPED_THP
))
1414 mm_slot
->pte_mapped_thp
[mm_slot
->nr_pte_mapped_thp
++] = addr
;
1415 spin_unlock(&khugepaged_mm_lock
);
1420 * collapse_pte_mapped_thp - Try to collapse a pte-mapped THP for mm at
1423 * @mm: process address space where collapse happens
1424 * @addr: THP collapse address
1426 * This function checks whether all the PTEs in the PMD are pointing to the
1427 * right THP. If so, retract the page table so the THP can refault in with
1430 void collapse_pte_mapped_thp(struct mm_struct
*mm
, unsigned long addr
)
1432 unsigned long haddr
= addr
& HPAGE_PMD_MASK
;
1433 struct vm_area_struct
*vma
= find_vma(mm
, haddr
);
1435 pte_t
*start_pte
, *pte
;
1441 if (!vma
|| !vma
->vm_file
||
1442 !range_in_vma(vma
, haddr
, haddr
+ HPAGE_PMD_SIZE
))
1446 * This vm_flags may not have VM_HUGEPAGE if the page was not
1447 * collapsed by this mm. But we can still collapse if the page is
1448 * the valid THP. Add extra VM_HUGEPAGE so hugepage_vma_check()
1449 * will not fail the vma for missing VM_HUGEPAGE
1451 if (!hugepage_vma_check(vma
, vma
->vm_flags
| VM_HUGEPAGE
))
1454 hpage
= find_lock_page(vma
->vm_file
->f_mapping
,
1455 linear_page_index(vma
, haddr
));
1459 if (!PageHead(hpage
))
1462 pmd
= mm_find_pmd(mm
, haddr
);
1466 start_pte
= pte_offset_map_lock(mm
, pmd
, haddr
, &ptl
);
1468 /* step 1: check all mapped PTEs are to the right huge page */
1469 for (i
= 0, addr
= haddr
, pte
= start_pte
;
1470 i
< HPAGE_PMD_NR
; i
++, addr
+= PAGE_SIZE
, pte
++) {
1473 /* empty pte, skip */
1477 /* page swapped out, abort */
1478 if (!pte_present(*pte
))
1481 page
= vm_normal_page(vma
, addr
, *pte
);
1484 * Note that uprobe, debugger, or MAP_PRIVATE may change the
1485 * page table, but the new page will not be a subpage of hpage.
1487 if (hpage
+ i
!= page
)
1492 /* step 2: adjust rmap */
1493 for (i
= 0, addr
= haddr
, pte
= start_pte
;
1494 i
< HPAGE_PMD_NR
; i
++, addr
+= PAGE_SIZE
, pte
++) {
1499 page
= vm_normal_page(vma
, addr
, *pte
);
1500 page_remove_rmap(page
, false);
1503 pte_unmap_unlock(start_pte
, ptl
);
1505 /* step 3: set proper refcount and mm_counters. */
1507 page_ref_sub(hpage
, count
);
1508 add_mm_counter(vma
->vm_mm
, mm_counter_file(hpage
), -count
);
1511 /* step 4: collapse pmd */
1512 ptl
= pmd_lock(vma
->vm_mm
, pmd
);
1513 _pmd
= pmdp_collapse_flush(vma
, haddr
, pmd
);
1516 pte_free(mm
, pmd_pgtable(_pmd
));
1524 pte_unmap_unlock(start_pte
, ptl
);
1528 static void khugepaged_collapse_pte_mapped_thps(struct mm_slot
*mm_slot
)
1530 struct mm_struct
*mm
= mm_slot
->mm
;
1533 if (likely(mm_slot
->nr_pte_mapped_thp
== 0))
1536 if (!mmap_write_trylock(mm
))
1539 if (unlikely(khugepaged_test_exit(mm
)))
1542 for (i
= 0; i
< mm_slot
->nr_pte_mapped_thp
; i
++)
1543 collapse_pte_mapped_thp(mm
, mm_slot
->pte_mapped_thp
[i
]);
1546 mm_slot
->nr_pte_mapped_thp
= 0;
1547 mmap_write_unlock(mm
);
1550 static void retract_page_tables(struct address_space
*mapping
, pgoff_t pgoff
)
1552 struct vm_area_struct
*vma
;
1553 struct mm_struct
*mm
;
1557 i_mmap_lock_write(mapping
);
1558 vma_interval_tree_foreach(vma
, &mapping
->i_mmap
, pgoff
, pgoff
) {
1560 * Check vma->anon_vma to exclude MAP_PRIVATE mappings that
1561 * got written to. These VMAs are likely not worth investing
1562 * mmap_write_lock(mm) as PMD-mapping is likely to be split
1565 * Not that vma->anon_vma check is racy: it can be set up after
1566 * the check but before we took mmap_lock by the fault path.
1567 * But page lock would prevent establishing any new ptes of the
1568 * page, so we are safe.
1570 * An alternative would be drop the check, but check that page
1571 * table is clear before calling pmdp_collapse_flush() under
1572 * ptl. It has higher chance to recover THP for the VMA, but
1573 * has higher cost too.
1577 addr
= vma
->vm_start
+ ((pgoff
- vma
->vm_pgoff
) << PAGE_SHIFT
);
1578 if (addr
& ~HPAGE_PMD_MASK
)
1580 if (vma
->vm_end
< addr
+ HPAGE_PMD_SIZE
)
1583 pmd
= mm_find_pmd(mm
, addr
);
1587 * We need exclusive mmap_lock to retract page table.
1589 * We use trylock due to lock inversion: we need to acquire
1590 * mmap_lock while holding page lock. Fault path does it in
1591 * reverse order. Trylock is a way to avoid deadlock.
1593 if (mmap_write_trylock(mm
)) {
1594 if (!khugepaged_test_exit(mm
)) {
1595 spinlock_t
*ptl
= pmd_lock(mm
, pmd
);
1596 /* assume page table is clear */
1597 _pmd
= pmdp_collapse_flush(vma
, addr
, pmd
);
1600 pte_free(mm
, pmd_pgtable(_pmd
));
1602 mmap_write_unlock(mm
);
1604 /* Try again later */
1605 khugepaged_add_pte_mapped_thp(mm
, addr
);
1608 i_mmap_unlock_write(mapping
);
1612 * collapse_file - collapse filemap/tmpfs/shmem pages into huge one.
1614 * @mm: process address space where collapse happens
1615 * @file: file that collapse on
1616 * @start: collapse start address
1617 * @hpage: new allocated huge page for collapse
1618 * @node: appointed node the new huge page allocate from
1620 * Basic scheme is simple, details are more complex:
1621 * - allocate and lock a new huge page;
1622 * - scan page cache replacing old pages with the new one
1623 * + swap/gup in pages if necessary;
1625 * + keep old pages around in case rollback is required;
1626 * - if replacing succeeds:
1629 * + unlock huge page;
1630 * - if replacing failed;
1631 * + put all pages back and unfreeze them;
1632 * + restore gaps in the page cache;
1633 * + unlock and free huge page;
1635 static void collapse_file(struct mm_struct
*mm
,
1636 struct file
*file
, pgoff_t start
,
1637 struct page
**hpage
, int node
)
1639 struct address_space
*mapping
= file
->f_mapping
;
1641 struct page
*new_page
;
1642 pgoff_t index
, end
= start
+ HPAGE_PMD_NR
;
1643 LIST_HEAD(pagelist
);
1644 XA_STATE_ORDER(xas
, &mapping
->i_pages
, start
, HPAGE_PMD_ORDER
);
1645 int nr_none
= 0, result
= SCAN_SUCCEED
;
1646 bool is_shmem
= shmem_file(file
);
1649 VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS
) && !is_shmem
);
1650 VM_BUG_ON(start
& (HPAGE_PMD_NR
- 1));
1652 /* Only allocate from the target node */
1653 gfp
= alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE
;
1655 new_page
= khugepaged_alloc_page(hpage
, gfp
, node
);
1657 result
= SCAN_ALLOC_HUGE_PAGE_FAIL
;
1661 if (unlikely(mem_cgroup_charge(new_page
, mm
, gfp
))) {
1662 result
= SCAN_CGROUP_CHARGE_FAIL
;
1665 count_memcg_page_event(new_page
, THP_COLLAPSE_ALLOC
);
1667 /* This will be less messy when we use multi-index entries */
1670 xas_create_range(&xas
);
1671 if (!xas_error(&xas
))
1673 xas_unlock_irq(&xas
);
1674 if (!xas_nomem(&xas
, GFP_KERNEL
)) {
1680 __SetPageLocked(new_page
);
1682 __SetPageSwapBacked(new_page
);
1683 new_page
->index
= start
;
1684 new_page
->mapping
= mapping
;
1687 * At this point the new_page is locked and not up-to-date.
1688 * It's safe to insert it into the page cache, because nobody would
1689 * be able to map it or use it in another way until we unlock it.
1692 xas_set(&xas
, start
);
1693 for (index
= start
; index
< end
; index
++) {
1694 struct page
*page
= xas_next(&xas
);
1696 VM_BUG_ON(index
!= xas
.xa_index
);
1700 * Stop if extent has been truncated or
1701 * hole-punched, and is now completely
1704 if (index
== start
) {
1705 if (!xas_next_entry(&xas
, end
- 1)) {
1706 result
= SCAN_TRUNCATED
;
1709 xas_set(&xas
, index
);
1711 if (!shmem_charge(mapping
->host
, 1)) {
1715 xas_store(&xas
, new_page
);
1720 if (xa_is_value(page
) || !PageUptodate(page
)) {
1721 xas_unlock_irq(&xas
);
1722 /* swap in or instantiate fallocated page */
1723 if (shmem_getpage(mapping
->host
, index
, &page
,
1728 } else if (trylock_page(page
)) {
1730 xas_unlock_irq(&xas
);
1732 result
= SCAN_PAGE_LOCK
;
1735 } else { /* !is_shmem */
1736 if (!page
|| xa_is_value(page
)) {
1737 xas_unlock_irq(&xas
);
1738 page_cache_sync_readahead(mapping
, &file
->f_ra
,
1741 /* drain pagevecs to help isolate_lru_page() */
1743 page
= find_lock_page(mapping
, index
);
1744 if (unlikely(page
== NULL
)) {
1748 } else if (PageDirty(page
)) {
1750 * khugepaged only works on read-only fd,
1751 * so this page is dirty because it hasn't
1752 * been flushed since first write. There
1753 * won't be new dirty pages.
1755 * Trigger async flush here and hope the
1756 * writeback is done when khugepaged
1757 * revisits this page.
1759 * This is a one-off situation. We are not
1760 * forcing writeback in loop.
1762 xas_unlock_irq(&xas
);
1763 filemap_flush(mapping
);
1766 } else if (trylock_page(page
)) {
1768 xas_unlock_irq(&xas
);
1770 result
= SCAN_PAGE_LOCK
;
1776 * The page must be locked, so we can drop the i_pages lock
1777 * without racing with truncate.
1779 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
1781 /* make sure the page is up to date */
1782 if (unlikely(!PageUptodate(page
))) {
1788 * If file was truncated then extended, or hole-punched, before
1789 * we locked the first page, then a THP might be there already.
1791 if (PageTransCompound(page
)) {
1792 result
= SCAN_PAGE_COMPOUND
;
1796 if (page_mapping(page
) != mapping
) {
1797 result
= SCAN_TRUNCATED
;
1801 if (!is_shmem
&& PageDirty(page
)) {
1803 * khugepaged only works on read-only fd, so this
1804 * page is dirty because it hasn't been flushed
1805 * since first write.
1811 if (isolate_lru_page(page
)) {
1812 result
= SCAN_DEL_PAGE_LRU
;
1816 if (page_has_private(page
) &&
1817 !try_to_release_page(page
, GFP_KERNEL
)) {
1818 result
= SCAN_PAGE_HAS_PRIVATE
;
1819 putback_lru_page(page
);
1823 if (page_mapped(page
))
1824 unmap_mapping_pages(mapping
, index
, 1, false);
1827 xas_set(&xas
, index
);
1829 VM_BUG_ON_PAGE(page
!= xas_load(&xas
), page
);
1830 VM_BUG_ON_PAGE(page_mapped(page
), page
);
1833 * The page is expected to have page_count() == 3:
1834 * - we hold a pin on it;
1835 * - one reference from page cache;
1836 * - one from isolate_lru_page;
1838 if (!page_ref_freeze(page
, 3)) {
1839 result
= SCAN_PAGE_COUNT
;
1840 xas_unlock_irq(&xas
);
1841 putback_lru_page(page
);
1846 * Add the page to the list to be able to undo the collapse if
1847 * something go wrong.
1849 list_add_tail(&page
->lru
, &pagelist
);
1851 /* Finally, replace with the new page. */
1852 xas_store(&xas
, new_page
);
1859 nr
= thp_nr_pages(new_page
);
1862 __mod_lruvec_page_state(new_page
, NR_SHMEM_THPS
, nr
);
1864 __mod_lruvec_page_state(new_page
, NR_FILE_THPS
, nr
);
1865 filemap_nr_thps_inc(mapping
);
1867 * Paired with smp_mb() in do_dentry_open() to ensure
1868 * i_writecount is up to date and the update to nr_thps is
1869 * visible. Ensures the page cache will be truncated if the
1870 * file is opened writable.
1873 if (inode_is_open_for_write(mapping
->host
)) {
1875 __mod_lruvec_page_state(new_page
, NR_FILE_THPS
, -nr
);
1876 filemap_nr_thps_dec(mapping
);
1882 __mod_lruvec_page_state(new_page
, NR_FILE_PAGES
, nr_none
);
1884 __mod_lruvec_page_state(new_page
, NR_SHMEM
, nr_none
);
1888 xas_unlock_irq(&xas
);
1891 if (result
== SCAN_SUCCEED
) {
1892 struct page
*page
, *tmp
;
1895 * Replacing old pages with new one has succeeded, now we
1896 * need to copy the content and free the old pages.
1899 list_for_each_entry_safe(page
, tmp
, &pagelist
, lru
) {
1900 while (index
< page
->index
) {
1901 clear_highpage(new_page
+ (index
% HPAGE_PMD_NR
));
1904 copy_highpage(new_page
+ (page
->index
% HPAGE_PMD_NR
),
1906 list_del(&page
->lru
);
1907 page
->mapping
= NULL
;
1908 page_ref_unfreeze(page
, 1);
1909 ClearPageActive(page
);
1910 ClearPageUnevictable(page
);
1915 while (index
< end
) {
1916 clear_highpage(new_page
+ (index
% HPAGE_PMD_NR
));
1920 SetPageUptodate(new_page
);
1921 page_ref_add(new_page
, HPAGE_PMD_NR
- 1);
1923 set_page_dirty(new_page
);
1924 lru_cache_add(new_page
);
1927 * Remove pte page tables, so we can re-fault the page as huge.
1929 retract_page_tables(mapping
, start
);
1932 khugepaged_pages_collapsed
++;
1936 /* Something went wrong: roll back page cache changes */
1938 mapping
->nrpages
-= nr_none
;
1941 shmem_uncharge(mapping
->host
, nr_none
);
1943 xas_set(&xas
, start
);
1944 xas_for_each(&xas
, page
, end
- 1) {
1945 page
= list_first_entry_or_null(&pagelist
,
1947 if (!page
|| xas
.xa_index
< page
->index
) {
1951 /* Put holes back where they were */
1952 xas_store(&xas
, NULL
);
1956 VM_BUG_ON_PAGE(page
->index
!= xas
.xa_index
, page
);
1958 /* Unfreeze the page. */
1959 list_del(&page
->lru
);
1960 page_ref_unfreeze(page
, 2);
1961 xas_store(&xas
, page
);
1963 xas_unlock_irq(&xas
);
1965 putback_lru_page(page
);
1969 xas_unlock_irq(&xas
);
1971 new_page
->mapping
= NULL
;
1974 unlock_page(new_page
);
1976 VM_BUG_ON(!list_empty(&pagelist
));
1977 if (!IS_ERR_OR_NULL(*hpage
))
1978 mem_cgroup_uncharge(*hpage
);
1979 /* TODO: tracepoints */
1982 static void khugepaged_scan_file(struct mm_struct
*mm
,
1983 struct file
*file
, pgoff_t start
, struct page
**hpage
)
1985 struct page
*page
= NULL
;
1986 struct address_space
*mapping
= file
->f_mapping
;
1987 XA_STATE(xas
, &mapping
->i_pages
, start
);
1989 int node
= NUMA_NO_NODE
;
1990 int result
= SCAN_SUCCEED
;
1994 memset(khugepaged_node_load
, 0, sizeof(khugepaged_node_load
));
1996 xas_for_each(&xas
, page
, start
+ HPAGE_PMD_NR
- 1) {
1997 if (xas_retry(&xas
, page
))
2000 if (xa_is_value(page
)) {
2001 if (++swap
> khugepaged_max_ptes_swap
) {
2002 result
= SCAN_EXCEED_SWAP_PTE
;
2008 if (PageTransCompound(page
)) {
2009 result
= SCAN_PAGE_COMPOUND
;
2013 node
= page_to_nid(page
);
2014 if (khugepaged_scan_abort(node
)) {
2015 result
= SCAN_SCAN_ABORT
;
2018 khugepaged_node_load
[node
]++;
2020 if (!PageLRU(page
)) {
2021 result
= SCAN_PAGE_LRU
;
2025 if (page_count(page
) !=
2026 1 + page_mapcount(page
) + page_has_private(page
)) {
2027 result
= SCAN_PAGE_COUNT
;
2032 * We probably should check if the page is referenced here, but
2033 * nobody would transfer pte_young() to PageReferenced() for us.
2034 * And rmap walk here is just too costly...
2039 if (need_resched()) {
2046 if (result
== SCAN_SUCCEED
) {
2047 if (present
< HPAGE_PMD_NR
- khugepaged_max_ptes_none
) {
2048 result
= SCAN_EXCEED_NONE_PTE
;
2050 node
= khugepaged_find_target_node();
2051 collapse_file(mm
, file
, start
, hpage
, node
);
2055 /* TODO: tracepoints */
2058 static void khugepaged_scan_file(struct mm_struct
*mm
,
2059 struct file
*file
, pgoff_t start
, struct page
**hpage
)
2064 static void khugepaged_collapse_pte_mapped_thps(struct mm_slot
*mm_slot
)
2069 static unsigned int khugepaged_scan_mm_slot(unsigned int pages
,
2070 struct page
**hpage
)
2071 __releases(&khugepaged_mm_lock
)
2072 __acquires(&khugepaged_mm_lock
)
2074 struct mm_slot
*mm_slot
;
2075 struct mm_struct
*mm
;
2076 struct vm_area_struct
*vma
;
2080 lockdep_assert_held(&khugepaged_mm_lock
);
2082 if (khugepaged_scan
.mm_slot
)
2083 mm_slot
= khugepaged_scan
.mm_slot
;
2085 mm_slot
= list_entry(khugepaged_scan
.mm_head
.next
,
2086 struct mm_slot
, mm_node
);
2087 khugepaged_scan
.address
= 0;
2088 khugepaged_scan
.mm_slot
= mm_slot
;
2090 spin_unlock(&khugepaged_mm_lock
);
2091 khugepaged_collapse_pte_mapped_thps(mm_slot
);
2095 * Don't wait for semaphore (to avoid long wait times). Just move to
2096 * the next mm on the list.
2099 if (unlikely(!mmap_read_trylock(mm
)))
2100 goto breakouterloop_mmap_lock
;
2101 if (likely(!khugepaged_test_exit(mm
)))
2102 vma
= find_vma(mm
, khugepaged_scan
.address
);
2105 for (; vma
; vma
= vma
->vm_next
) {
2106 unsigned long hstart
, hend
;
2109 if (unlikely(khugepaged_test_exit(mm
))) {
2113 if (!hugepage_vma_check(vma
, vma
->vm_flags
)) {
2118 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
2119 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
2122 if (khugepaged_scan
.address
> hend
)
2124 if (khugepaged_scan
.address
< hstart
)
2125 khugepaged_scan
.address
= hstart
;
2126 VM_BUG_ON(khugepaged_scan
.address
& ~HPAGE_PMD_MASK
);
2127 if (shmem_file(vma
->vm_file
) && !shmem_huge_enabled(vma
))
2130 while (khugepaged_scan
.address
< hend
) {
2133 if (unlikely(khugepaged_test_exit(mm
)))
2134 goto breakouterloop
;
2136 VM_BUG_ON(khugepaged_scan
.address
< hstart
||
2137 khugepaged_scan
.address
+ HPAGE_PMD_SIZE
>
2139 if (IS_ENABLED(CONFIG_SHMEM
) && vma
->vm_file
) {
2140 struct file
*file
= get_file(vma
->vm_file
);
2141 pgoff_t pgoff
= linear_page_index(vma
,
2142 khugepaged_scan
.address
);
2144 mmap_read_unlock(mm
);
2146 khugepaged_scan_file(mm
, file
, pgoff
, hpage
);
2149 ret
= khugepaged_scan_pmd(mm
, vma
,
2150 khugepaged_scan
.address
,
2153 /* move to next address */
2154 khugepaged_scan
.address
+= HPAGE_PMD_SIZE
;
2155 progress
+= HPAGE_PMD_NR
;
2157 /* we released mmap_lock so break loop */
2158 goto breakouterloop_mmap_lock
;
2159 if (progress
>= pages
)
2160 goto breakouterloop
;
2164 mmap_read_unlock(mm
); /* exit_mmap will destroy ptes after this */
2165 breakouterloop_mmap_lock
:
2167 spin_lock(&khugepaged_mm_lock
);
2168 VM_BUG_ON(khugepaged_scan
.mm_slot
!= mm_slot
);
2170 * Release the current mm_slot if this mm is about to die, or
2171 * if we scanned all vmas of this mm.
2173 if (khugepaged_test_exit(mm
) || !vma
) {
2175 * Make sure that if mm_users is reaching zero while
2176 * khugepaged runs here, khugepaged_exit will find
2177 * mm_slot not pointing to the exiting mm.
2179 if (mm_slot
->mm_node
.next
!= &khugepaged_scan
.mm_head
) {
2180 khugepaged_scan
.mm_slot
= list_entry(
2181 mm_slot
->mm_node
.next
,
2182 struct mm_slot
, mm_node
);
2183 khugepaged_scan
.address
= 0;
2185 khugepaged_scan
.mm_slot
= NULL
;
2186 khugepaged_full_scans
++;
2189 collect_mm_slot(mm_slot
);
2195 static int khugepaged_has_work(void)
2197 return !list_empty(&khugepaged_scan
.mm_head
) &&
2198 khugepaged_enabled();
2201 static int khugepaged_wait_event(void)
2203 return !list_empty(&khugepaged_scan
.mm_head
) ||
2204 kthread_should_stop();
2207 static void khugepaged_do_scan(void)
2209 struct page
*hpage
= NULL
;
2210 unsigned int progress
= 0, pass_through_head
= 0;
2211 unsigned int pages
= READ_ONCE(khugepaged_pages_to_scan
);
2214 lru_add_drain_all();
2216 while (progress
< pages
) {
2217 if (!khugepaged_prealloc_page(&hpage
, &wait
))
2222 if (unlikely(kthread_should_stop() || try_to_freeze()))
2225 spin_lock(&khugepaged_mm_lock
);
2226 if (!khugepaged_scan
.mm_slot
)
2227 pass_through_head
++;
2228 if (khugepaged_has_work() &&
2229 pass_through_head
< 2)
2230 progress
+= khugepaged_scan_mm_slot(pages
- progress
,
2234 spin_unlock(&khugepaged_mm_lock
);
2237 if (!IS_ERR_OR_NULL(hpage
))
2241 static bool khugepaged_should_wakeup(void)
2243 return kthread_should_stop() ||
2244 time_after_eq(jiffies
, khugepaged_sleep_expire
);
2247 static void khugepaged_wait_work(void)
2249 if (khugepaged_has_work()) {
2250 const unsigned long scan_sleep_jiffies
=
2251 msecs_to_jiffies(khugepaged_scan_sleep_millisecs
);
2253 if (!scan_sleep_jiffies
)
2256 khugepaged_sleep_expire
= jiffies
+ scan_sleep_jiffies
;
2257 wait_event_freezable_timeout(khugepaged_wait
,
2258 khugepaged_should_wakeup(),
2259 scan_sleep_jiffies
);
2263 if (khugepaged_enabled())
2264 wait_event_freezable(khugepaged_wait
, khugepaged_wait_event());
2267 static int khugepaged(void *none
)
2269 struct mm_slot
*mm_slot
;
2272 set_user_nice(current
, MAX_NICE
);
2274 while (!kthread_should_stop()) {
2275 khugepaged_do_scan();
2276 khugepaged_wait_work();
2279 spin_lock(&khugepaged_mm_lock
);
2280 mm_slot
= khugepaged_scan
.mm_slot
;
2281 khugepaged_scan
.mm_slot
= NULL
;
2283 collect_mm_slot(mm_slot
);
2284 spin_unlock(&khugepaged_mm_lock
);
2288 static void set_recommended_min_free_kbytes(void)
2292 unsigned long recommended_min
;
2294 for_each_populated_zone(zone
) {
2296 * We don't need to worry about fragmentation of
2297 * ZONE_MOVABLE since it only has movable pages.
2299 if (zone_idx(zone
) > gfp_zone(GFP_USER
))
2305 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */
2306 recommended_min
= pageblock_nr_pages
* nr_zones
* 2;
2309 * Make sure that on average at least two pageblocks are almost free
2310 * of another type, one for a migratetype to fall back to and a
2311 * second to avoid subsequent fallbacks of other types There are 3
2312 * MIGRATE_TYPES we care about.
2314 recommended_min
+= pageblock_nr_pages
* nr_zones
*
2315 MIGRATE_PCPTYPES
* MIGRATE_PCPTYPES
;
2317 /* don't ever allow to reserve more than 5% of the lowmem */
2318 recommended_min
= min(recommended_min
,
2319 (unsigned long) nr_free_buffer_pages() / 20);
2320 recommended_min
<<= (PAGE_SHIFT
-10);
2322 if (recommended_min
> min_free_kbytes
) {
2323 if (user_min_free_kbytes
>= 0)
2324 pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n",
2325 min_free_kbytes
, recommended_min
);
2327 min_free_kbytes
= recommended_min
;
2329 setup_per_zone_wmarks();
2332 int start_stop_khugepaged(void)
2336 mutex_lock(&khugepaged_mutex
);
2337 if (khugepaged_enabled()) {
2338 if (!khugepaged_thread
)
2339 khugepaged_thread
= kthread_run(khugepaged
, NULL
,
2341 if (IS_ERR(khugepaged_thread
)) {
2342 pr_err("khugepaged: kthread_run(khugepaged) failed\n");
2343 err
= PTR_ERR(khugepaged_thread
);
2344 khugepaged_thread
= NULL
;
2348 if (!list_empty(&khugepaged_scan
.mm_head
))
2349 wake_up_interruptible(&khugepaged_wait
);
2351 set_recommended_min_free_kbytes();
2352 } else if (khugepaged_thread
) {
2353 kthread_stop(khugepaged_thread
);
2354 khugepaged_thread
= NULL
;
2357 mutex_unlock(&khugepaged_mutex
);
2361 void khugepaged_min_free_kbytes_update(void)
2363 mutex_lock(&khugepaged_mutex
);
2364 if (khugepaged_enabled() && khugepaged_thread
)
2365 set_recommended_min_free_kbytes();
2366 mutex_unlock(&khugepaged_mutex
);