1 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
4 #include <linux/sched.h>
5 #include <linux/mmu_notifier.h>
6 #include <linux/rmap.h>
7 #include <linux/swap.h>
8 #include <linux/mm_inline.h>
9 #include <linux/kthread.h>
10 #include <linux/khugepaged.h>
11 #include <linux/freezer.h>
12 #include <linux/mman.h>
13 #include <linux/hashtable.h>
14 #include <linux/userfaultfd_k.h>
15 #include <linux/page_idle.h>
16 #include <linux/swapops.h>
17 #include <linux/shmem_fs.h>
20 #include <asm/pgalloc.h>
30 SCAN_LACK_REFERENCED_PAGE,
44 SCAN_ALLOC_HUGE_PAGE_FAIL,
45 SCAN_CGROUP_CHARGE_FAIL,
50 #define CREATE_TRACE_POINTS
51 #include <trace/events/huge_memory.h>
53 /* default scan 8*512 pte (or vmas) every 30 second */
54 static unsigned int khugepaged_pages_to_scan __read_mostly;
55 static unsigned int khugepaged_pages_collapsed;
56 static unsigned int khugepaged_full_scans;
57 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
58 /* during fragmentation poll the hugepage allocator once every minute */
59 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
60 static unsigned long khugepaged_sleep_expire;
61 static DEFINE_SPINLOCK(khugepaged_mm_lock);
62 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
64 * default collapse hugepages if there is at least one pte mapped like
65 * it would have happened if the vma was large enough during page
68 static unsigned int khugepaged_max_ptes_none __read_mostly;
69 static unsigned int khugepaged_max_ptes_swap __read_mostly;
71 #define MM_SLOTS_HASH_BITS 10
72 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
74 static struct kmem_cache *mm_slot_cache __read_mostly;
77 * struct mm_slot - hash lookup from mm to mm_slot
78 * @hash: hash collision list
79 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
80 * @mm: the mm that this information is valid for
83 struct hlist_node hash;
84 struct list_head mm_node;
89 * struct khugepaged_scan - cursor for scanning
90 * @mm_head: the head of the mm list to scan
91 * @mm_slot: the current mm_slot we are scanning
92 * @address: the next address inside that to be scanned
94 * There is only the one khugepaged_scan instance of this cursor structure.
96 struct khugepaged_scan {
97 struct list_head mm_head;
98 struct mm_slot *mm_slot;
99 unsigned long address;
102 static struct khugepaged_scan khugepaged_scan = {
103 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
107 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
108 struct kobj_attribute *attr,
111 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
114 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
115 struct kobj_attribute *attr,
116 const char *buf, size_t count)
121 err = kstrtoul(buf, 10, &msecs);
122 if (err || msecs > UINT_MAX)
125 khugepaged_scan_sleep_millisecs = msecs;
126 khugepaged_sleep_expire = 0;
127 wake_up_interruptible(&khugepaged_wait);
131 static struct kobj_attribute scan_sleep_millisecs_attr =
132 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
133 scan_sleep_millisecs_store);
135 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
136 struct kobj_attribute *attr,
139 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
142 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
143 struct kobj_attribute *attr,
144 const char *buf, size_t count)
149 err = kstrtoul(buf, 10, &msecs);
150 if (err || msecs > UINT_MAX)
153 khugepaged_alloc_sleep_millisecs = msecs;
154 khugepaged_sleep_expire = 0;
155 wake_up_interruptible(&khugepaged_wait);
159 static struct kobj_attribute alloc_sleep_millisecs_attr =
160 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
161 alloc_sleep_millisecs_store);
163 static ssize_t pages_to_scan_show(struct kobject *kobj,
164 struct kobj_attribute *attr,
167 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
169 static ssize_t pages_to_scan_store(struct kobject *kobj,
170 struct kobj_attribute *attr,
171 const char *buf, size_t count)
176 err = kstrtoul(buf, 10, &pages);
177 if (err || !pages || pages > UINT_MAX)
180 khugepaged_pages_to_scan = pages;
184 static struct kobj_attribute pages_to_scan_attr =
185 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
186 pages_to_scan_store);
188 static ssize_t pages_collapsed_show(struct kobject *kobj,
189 struct kobj_attribute *attr,
192 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
194 static struct kobj_attribute pages_collapsed_attr =
195 __ATTR_RO(pages_collapsed);
197 static ssize_t full_scans_show(struct kobject *kobj,
198 struct kobj_attribute *attr,
201 return sprintf(buf, "%u\n", khugepaged_full_scans);
203 static struct kobj_attribute full_scans_attr =
204 __ATTR_RO(full_scans);
206 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
207 struct kobj_attribute *attr, char *buf)
209 return single_hugepage_flag_show(kobj, attr, buf,
210 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
212 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
213 struct kobj_attribute *attr,
214 const char *buf, size_t count)
216 return single_hugepage_flag_store(kobj, attr, buf, count,
217 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
219 static struct kobj_attribute khugepaged_defrag_attr =
220 __ATTR(defrag, 0644, khugepaged_defrag_show,
221 khugepaged_defrag_store);
224 * max_ptes_none controls if khugepaged should collapse hugepages over
225 * any unmapped ptes in turn potentially increasing the memory
226 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
227 * reduce the available free memory in the system as it
228 * runs. Increasing max_ptes_none will instead potentially reduce the
229 * free memory in the system during the khugepaged scan.
231 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
232 struct kobj_attribute *attr,
235 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
237 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
238 struct kobj_attribute *attr,
239 const char *buf, size_t count)
242 unsigned long max_ptes_none;
244 err = kstrtoul(buf, 10, &max_ptes_none);
245 if (err || max_ptes_none > HPAGE_PMD_NR-1)
248 khugepaged_max_ptes_none = max_ptes_none;
252 static struct kobj_attribute khugepaged_max_ptes_none_attr =
253 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
254 khugepaged_max_ptes_none_store);
256 static ssize_t khugepaged_max_ptes_swap_show(struct kobject *kobj,
257 struct kobj_attribute *attr,
260 return sprintf(buf, "%u\n", khugepaged_max_ptes_swap);
263 static ssize_t khugepaged_max_ptes_swap_store(struct kobject *kobj,
264 struct kobj_attribute *attr,
265 const char *buf, size_t count)
268 unsigned long max_ptes_swap;
270 err = kstrtoul(buf, 10, &max_ptes_swap);
271 if (err || max_ptes_swap > HPAGE_PMD_NR-1)
274 khugepaged_max_ptes_swap = max_ptes_swap;
279 static struct kobj_attribute khugepaged_max_ptes_swap_attr =
280 __ATTR(max_ptes_swap, 0644, khugepaged_max_ptes_swap_show,
281 khugepaged_max_ptes_swap_store);
283 static struct attribute *khugepaged_attr[] = {
284 &khugepaged_defrag_attr.attr,
285 &khugepaged_max_ptes_none_attr.attr,
286 &pages_to_scan_attr.attr,
287 &pages_collapsed_attr.attr,
288 &full_scans_attr.attr,
289 &scan_sleep_millisecs_attr.attr,
290 &alloc_sleep_millisecs_attr.attr,
291 &khugepaged_max_ptes_swap_attr.attr,
295 struct attribute_group khugepaged_attr_group = {
296 .attrs = khugepaged_attr,
297 .name = "khugepaged",
299 #endif /* CONFIG_SYSFS */
301 #define VM_NO_KHUGEPAGED (VM_SPECIAL | VM_HUGETLB)
303 int hugepage_madvise(struct vm_area_struct *vma,
304 unsigned long *vm_flags, int advice)
310 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
311 * can't handle this properly after s390_enable_sie, so we simply
312 * ignore the madvise to prevent qemu from causing a SIGSEGV.
314 if (mm_has_pgste(vma->vm_mm))
317 *vm_flags &= ~VM_NOHUGEPAGE;
318 *vm_flags |= VM_HUGEPAGE;
320 * If the vma become good for khugepaged to scan,
321 * register it here without waiting a page fault that
322 * may not happen any time soon.
324 if (!(*vm_flags & VM_NO_KHUGEPAGED) &&
325 khugepaged_enter_vma_merge(vma, *vm_flags))
328 case MADV_NOHUGEPAGE:
329 *vm_flags &= ~VM_HUGEPAGE;
330 *vm_flags |= VM_NOHUGEPAGE;
332 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
333 * this vma even if we leave the mm registered in khugepaged if
334 * it got registered before VM_NOHUGEPAGE was set.
342 int __init khugepaged_init(void)
344 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
345 sizeof(struct mm_slot),
346 __alignof__(struct mm_slot), 0, NULL);
350 khugepaged_pages_to_scan = HPAGE_PMD_NR * 8;
351 khugepaged_max_ptes_none = HPAGE_PMD_NR - 1;
352 khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8;
357 void __init khugepaged_destroy(void)
359 kmem_cache_destroy(mm_slot_cache);
362 static inline struct mm_slot *alloc_mm_slot(void)
364 if (!mm_slot_cache) /* initialization failed */
366 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
369 static inline void free_mm_slot(struct mm_slot *mm_slot)
371 kmem_cache_free(mm_slot_cache, mm_slot);
374 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
376 struct mm_slot *mm_slot;
378 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
379 if (mm == mm_slot->mm)
385 static void insert_to_mm_slots_hash(struct mm_struct *mm,
386 struct mm_slot *mm_slot)
389 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
392 static inline int khugepaged_test_exit(struct mm_struct *mm)
394 return atomic_read(&mm->mm_users) == 0;
397 int __khugepaged_enter(struct mm_struct *mm)
399 struct mm_slot *mm_slot;
402 mm_slot = alloc_mm_slot();
406 /* __khugepaged_exit() must not run from under us */
407 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
408 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
409 free_mm_slot(mm_slot);
413 spin_lock(&khugepaged_mm_lock);
414 insert_to_mm_slots_hash(mm, mm_slot);
416 * Insert just behind the scanning cursor, to let the area settle
419 wakeup = list_empty(&khugepaged_scan.mm_head);
420 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
421 spin_unlock(&khugepaged_mm_lock);
423 atomic_inc(&mm->mm_count);
425 wake_up_interruptible(&khugepaged_wait);
430 int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
431 unsigned long vm_flags)
433 unsigned long hstart, hend;
436 * Not yet faulted in so we will register later in the
437 * page fault if needed.
440 if (vma->vm_ops || (vm_flags & VM_NO_KHUGEPAGED))
441 /* khugepaged not yet working on file or special mappings */
443 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
444 hend = vma->vm_end & HPAGE_PMD_MASK;
446 return khugepaged_enter(vma, vm_flags);
450 void __khugepaged_exit(struct mm_struct *mm)
452 struct mm_slot *mm_slot;
455 spin_lock(&khugepaged_mm_lock);
456 mm_slot = get_mm_slot(mm);
457 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
458 hash_del(&mm_slot->hash);
459 list_del(&mm_slot->mm_node);
462 spin_unlock(&khugepaged_mm_lock);
465 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
466 free_mm_slot(mm_slot);
468 } else if (mm_slot) {
470 * This is required to serialize against
471 * khugepaged_test_exit() (which is guaranteed to run
472 * under mmap sem read mode). Stop here (after we
473 * return all pagetables will be destroyed) until
474 * khugepaged has finished working on the pagetables
475 * under the mmap_sem.
477 down_write(&mm->mmap_sem);
478 up_write(&mm->mmap_sem);
482 static void release_pte_page(struct page *page)
484 /* 0 stands for page_is_file_cache(page) == false */
485 dec_node_page_state(page, NR_ISOLATED_ANON + 0);
487 putback_lru_page(page);
490 static void release_pte_pages(pte_t *pte, pte_t *_pte)
492 while (--_pte >= pte) {
493 pte_t pteval = *_pte;
494 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)))
495 release_pte_page(pte_page(pteval));
499 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
500 unsigned long address,
503 struct page *page = NULL;
505 int none_or_zero = 0, result = 0, referenced = 0;
506 bool writable = false;
508 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
509 _pte++, address += PAGE_SIZE) {
510 pte_t pteval = *_pte;
511 if (pte_none(pteval) || (pte_present(pteval) &&
512 is_zero_pfn(pte_pfn(pteval)))) {
513 if (!userfaultfd_armed(vma) &&
514 ++none_or_zero <= khugepaged_max_ptes_none) {
517 result = SCAN_EXCEED_NONE_PTE;
521 if (!pte_present(pteval)) {
522 result = SCAN_PTE_NON_PRESENT;
525 page = vm_normal_page(vma, address, pteval);
526 if (unlikely(!page)) {
527 result = SCAN_PAGE_NULL;
531 /* TODO: teach khugepaged to collapse THP mapped with pte */
532 if (PageCompound(page)) {
533 result = SCAN_PAGE_COMPOUND;
537 VM_BUG_ON_PAGE(!PageAnon(page), page);
538 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
541 * We can do it before isolate_lru_page because the
542 * page can't be freed from under us. NOTE: PG_lock
543 * is needed to serialize against split_huge_page
544 * when invoked from the VM.
546 if (!trylock_page(page)) {
547 result = SCAN_PAGE_LOCK;
552 * cannot use mapcount: can't collapse if there's a gup pin.
553 * The page must only be referenced by the scanned process
554 * and page swap cache.
556 if (page_count(page) != 1 + !!PageSwapCache(page)) {
558 result = SCAN_PAGE_COUNT;
561 if (pte_write(pteval)) {
564 if (PageSwapCache(page) &&
565 !reuse_swap_page(page, NULL)) {
567 result = SCAN_SWAP_CACHE_PAGE;
571 * Page is not in the swap cache. It can be collapsed
577 * Isolate the page to avoid collapsing an hugepage
578 * currently in use by the VM.
580 if (isolate_lru_page(page)) {
582 result = SCAN_DEL_PAGE_LRU;
585 /* 0 stands for page_is_file_cache(page) == false */
586 inc_node_page_state(page, NR_ISOLATED_ANON + 0);
587 VM_BUG_ON_PAGE(!PageLocked(page), page);
588 VM_BUG_ON_PAGE(PageLRU(page), page);
590 /* There should be enough young pte to collapse the page */
591 if (pte_young(pteval) ||
592 page_is_young(page) || PageReferenced(page) ||
593 mmu_notifier_test_young(vma->vm_mm, address))
596 if (likely(writable)) {
597 if (likely(referenced)) {
598 result = SCAN_SUCCEED;
599 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
600 referenced, writable, result);
604 result = SCAN_PAGE_RO;
608 release_pte_pages(pte, _pte);
609 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
610 referenced, writable, result);
614 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
615 struct vm_area_struct *vma,
616 unsigned long address,
620 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
621 pte_t pteval = *_pte;
622 struct page *src_page;
624 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
625 clear_user_highpage(page, address);
626 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
627 if (is_zero_pfn(pte_pfn(pteval))) {
629 * ptl mostly unnecessary.
633 * paravirt calls inside pte_clear here are
636 pte_clear(vma->vm_mm, address, _pte);
640 src_page = pte_page(pteval);
641 copy_user_highpage(page, src_page, address, vma);
642 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page);
643 release_pte_page(src_page);
645 * ptl mostly unnecessary, but preempt has to
646 * be disabled to update the per-cpu stats
647 * inside page_remove_rmap().
651 * paravirt calls inside pte_clear here are
654 pte_clear(vma->vm_mm, address, _pte);
655 page_remove_rmap(src_page, false);
657 free_page_and_swap_cache(src_page);
660 address += PAGE_SIZE;
665 static void khugepaged_alloc_sleep(void)
669 add_wait_queue(&khugepaged_wait, &wait);
670 freezable_schedule_timeout_interruptible(
671 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
672 remove_wait_queue(&khugepaged_wait, &wait);
675 static int khugepaged_node_load[MAX_NUMNODES];
677 static bool khugepaged_scan_abort(int nid)
682 * If node_reclaim_mode is disabled, then no extra effort is made to
683 * allocate memory locally.
685 if (!node_reclaim_mode)
688 /* If there is a count for this node already, it must be acceptable */
689 if (khugepaged_node_load[nid])
692 for (i = 0; i < MAX_NUMNODES; i++) {
693 if (!khugepaged_node_load[i])
695 if (node_distance(nid, i) > RECLAIM_DISTANCE)
701 /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */
702 static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void)
704 return khugepaged_defrag() ? GFP_TRANSHUGE : GFP_TRANSHUGE_LIGHT;
708 static int khugepaged_find_target_node(void)
710 static int last_khugepaged_target_node = NUMA_NO_NODE;
711 int nid, target_node = 0, max_value = 0;
713 /* find first node with max normal pages hit */
714 for (nid = 0; nid < MAX_NUMNODES; nid++)
715 if (khugepaged_node_load[nid] > max_value) {
716 max_value = khugepaged_node_load[nid];
720 /* do some balance if several nodes have the same hit record */
721 if (target_node <= last_khugepaged_target_node)
722 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
724 if (max_value == khugepaged_node_load[nid]) {
729 last_khugepaged_target_node = target_node;
733 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
735 if (IS_ERR(*hpage)) {
741 khugepaged_alloc_sleep();
751 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
753 VM_BUG_ON_PAGE(*hpage, *hpage);
755 *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
756 if (unlikely(!*hpage)) {
757 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
758 *hpage = ERR_PTR(-ENOMEM);
762 prep_transhuge_page(*hpage);
763 count_vm_event(THP_COLLAPSE_ALLOC);
767 static int khugepaged_find_target_node(void)
772 static inline struct page *alloc_khugepaged_hugepage(void)
776 page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(),
779 prep_transhuge_page(page);
783 static struct page *khugepaged_alloc_hugepage(bool *wait)
788 hpage = alloc_khugepaged_hugepage();
790 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
795 khugepaged_alloc_sleep();
797 count_vm_event(THP_COLLAPSE_ALLOC);
798 } while (unlikely(!hpage) && likely(khugepaged_enabled()));
803 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
806 *hpage = khugepaged_alloc_hugepage(wait);
808 if (unlikely(!*hpage))
815 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
823 static bool hugepage_vma_check(struct vm_area_struct *vma)
825 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
826 (vma->vm_flags & VM_NOHUGEPAGE))
828 if (shmem_file(vma->vm_file)) {
829 if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
831 return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff,
834 if (!vma->anon_vma || vma->vm_ops)
836 if (is_vma_temporary_stack(vma))
838 return !(vma->vm_flags & VM_NO_KHUGEPAGED);
842 * If mmap_sem temporarily dropped, revalidate vma
843 * before taking mmap_sem.
844 * Return 0 if succeeds, otherwise return none-zero
848 static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
849 struct vm_area_struct **vmap)
851 struct vm_area_struct *vma;
852 unsigned long hstart, hend;
854 if (unlikely(khugepaged_test_exit(mm)))
855 return SCAN_ANY_PROCESS;
857 *vmap = vma = find_vma(mm, address);
859 return SCAN_VMA_NULL;
861 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
862 hend = vma->vm_end & HPAGE_PMD_MASK;
863 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
864 return SCAN_ADDRESS_RANGE;
865 if (!hugepage_vma_check(vma))
866 return SCAN_VMA_CHECK;
871 * Bring missing pages in from swap, to complete THP collapse.
872 * Only done if khugepaged_scan_pmd believes it is worthwhile.
874 * Called and returns without pte mapped or spinlocks held,
875 * but with mmap_sem held to protect against vma changes.
878 static bool __collapse_huge_page_swapin(struct mm_struct *mm,
879 struct vm_area_struct *vma,
880 unsigned long address, pmd_t *pmd,
884 int swapped_in = 0, ret = 0;
885 struct fault_env fe = {
888 .flags = FAULT_FLAG_ALLOW_RETRY,
892 /* we only decide to swapin, if there is enough young ptes */
893 if (referenced < HPAGE_PMD_NR/2) {
894 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
897 fe.pte = pte_offset_map(pmd, address);
898 for (; fe.address < address + HPAGE_PMD_NR*PAGE_SIZE;
899 fe.pte++, fe.address += PAGE_SIZE) {
901 if (!is_swap_pte(pteval))
904 ret = do_swap_page(&fe, pteval);
906 /* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */
907 if (ret & VM_FAULT_RETRY) {
908 down_read(&mm->mmap_sem);
909 if (hugepage_vma_revalidate(mm, address, &fe.vma)) {
910 /* vma is no longer available, don't continue to swapin */
911 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
914 /* check if the pmd is still valid */
915 if (mm_find_pmd(mm, address) != pmd)
918 if (ret & VM_FAULT_ERROR) {
919 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
922 /* pte is unmapped now, we need to map it */
923 fe.pte = pte_offset_map(pmd, fe.address);
927 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1);
931 static void collapse_huge_page(struct mm_struct *mm,
932 unsigned long address,
934 int node, int referenced)
939 struct page *new_page;
940 spinlock_t *pmd_ptl, *pte_ptl;
941 int isolated = 0, result = 0;
942 struct mem_cgroup *memcg;
943 struct vm_area_struct *vma;
944 unsigned long mmun_start; /* For mmu_notifiers */
945 unsigned long mmun_end; /* For mmu_notifiers */
948 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
950 /* Only allocate from the target node */
951 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_OTHER_NODE | __GFP_THISNODE;
954 * Before allocating the hugepage, release the mmap_sem read lock.
955 * The allocation can take potentially a long time if it involves
956 * sync compaction, and we do not need to hold the mmap_sem during
957 * that. We will recheck the vma after taking it again in write mode.
959 up_read(&mm->mmap_sem);
960 new_page = khugepaged_alloc_page(hpage, gfp, node);
962 result = SCAN_ALLOC_HUGE_PAGE_FAIL;
966 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
967 result = SCAN_CGROUP_CHARGE_FAIL;
971 down_read(&mm->mmap_sem);
972 result = hugepage_vma_revalidate(mm, address, &vma);
974 mem_cgroup_cancel_charge(new_page, memcg, true);
975 up_read(&mm->mmap_sem);
979 pmd = mm_find_pmd(mm, address);
981 result = SCAN_PMD_NULL;
982 mem_cgroup_cancel_charge(new_page, memcg, true);
983 up_read(&mm->mmap_sem);
988 * __collapse_huge_page_swapin always returns with mmap_sem locked.
989 * If it fails, we release mmap_sem and jump out_nolock.
990 * Continuing to collapse causes inconsistency.
992 if (!__collapse_huge_page_swapin(mm, vma, address, pmd, referenced)) {
993 mem_cgroup_cancel_charge(new_page, memcg, true);
994 up_read(&mm->mmap_sem);
998 up_read(&mm->mmap_sem);
1000 * Prevent all access to pagetables with the exception of
1001 * gup_fast later handled by the ptep_clear_flush and the VM
1002 * handled by the anon_vma lock + PG_lock.
1004 down_write(&mm->mmap_sem);
1005 result = hugepage_vma_revalidate(mm, address, &vma);
1008 /* check if the pmd is still valid */
1009 if (mm_find_pmd(mm, address) != pmd)
1012 anon_vma_lock_write(vma->anon_vma);
1014 pte = pte_offset_map(pmd, address);
1015 pte_ptl = pte_lockptr(mm, pmd);
1017 mmun_start = address;
1018 mmun_end = address + HPAGE_PMD_SIZE;
1019 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1020 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
1022 * After this gup_fast can't run anymore. This also removes
1023 * any huge TLB entry from the CPU so we won't allow
1024 * huge and small TLB entries for the same virtual address
1025 * to avoid the risk of CPU bugs in that area.
1027 _pmd = pmdp_collapse_flush(vma, address, pmd);
1028 spin_unlock(pmd_ptl);
1029 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1032 isolated = __collapse_huge_page_isolate(vma, address, pte);
1033 spin_unlock(pte_ptl);
1035 if (unlikely(!isolated)) {
1038 BUG_ON(!pmd_none(*pmd));
1040 * We can only use set_pmd_at when establishing
1041 * hugepmds and never for establishing regular pmds that
1042 * points to regular pagetables. Use pmd_populate for that
1044 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
1045 spin_unlock(pmd_ptl);
1046 anon_vma_unlock_write(vma->anon_vma);
1052 * All pages are isolated and locked so anon_vma rmap
1053 * can't run anymore.
1055 anon_vma_unlock_write(vma->anon_vma);
1057 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl);
1059 __SetPageUptodate(new_page);
1060 pgtable = pmd_pgtable(_pmd);
1062 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
1063 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
1066 * spin_lock() below is not the equivalent of smp_wmb(), so
1067 * this is needed to avoid the copy_huge_page writes to become
1068 * visible after the set_pmd_at() write.
1073 BUG_ON(!pmd_none(*pmd));
1074 page_add_new_anon_rmap(new_page, vma, address, true);
1075 mem_cgroup_commit_charge(new_page, memcg, false, true);
1076 lru_cache_add_active_or_unevictable(new_page, vma);
1077 pgtable_trans_huge_deposit(mm, pmd, pgtable);
1078 set_pmd_at(mm, address, pmd, _pmd);
1079 update_mmu_cache_pmd(vma, address, pmd);
1080 spin_unlock(pmd_ptl);
1084 khugepaged_pages_collapsed++;
1085 result = SCAN_SUCCEED;
1087 up_write(&mm->mmap_sem);
1089 trace_mm_collapse_huge_page(mm, isolated, result);
1092 mem_cgroup_cancel_charge(new_page, memcg, true);
1096 static int khugepaged_scan_pmd(struct mm_struct *mm,
1097 struct vm_area_struct *vma,
1098 unsigned long address,
1099 struct page **hpage)
1103 int ret = 0, none_or_zero = 0, result = 0, referenced = 0;
1104 struct page *page = NULL;
1105 unsigned long _address;
1107 int node = NUMA_NO_NODE, unmapped = 0;
1108 bool writable = false;
1110 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1112 pmd = mm_find_pmd(mm, address);
1114 result = SCAN_PMD_NULL;
1118 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
1119 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1120 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
1121 _pte++, _address += PAGE_SIZE) {
1122 pte_t pteval = *_pte;
1123 if (is_swap_pte(pteval)) {
1124 if (++unmapped <= khugepaged_max_ptes_swap) {
1127 result = SCAN_EXCEED_SWAP_PTE;
1131 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
1132 if (!userfaultfd_armed(vma) &&
1133 ++none_or_zero <= khugepaged_max_ptes_none) {
1136 result = SCAN_EXCEED_NONE_PTE;
1140 if (!pte_present(pteval)) {
1141 result = SCAN_PTE_NON_PRESENT;
1144 if (pte_write(pteval))
1147 page = vm_normal_page(vma, _address, pteval);
1148 if (unlikely(!page)) {
1149 result = SCAN_PAGE_NULL;
1153 /* TODO: teach khugepaged to collapse THP mapped with pte */
1154 if (PageCompound(page)) {
1155 result = SCAN_PAGE_COMPOUND;
1160 * Record which node the original page is from and save this
1161 * information to khugepaged_node_load[].
1162 * Khupaged will allocate hugepage from the node has the max
1165 node = page_to_nid(page);
1166 if (khugepaged_scan_abort(node)) {
1167 result = SCAN_SCAN_ABORT;
1170 khugepaged_node_load[node]++;
1171 if (!PageLRU(page)) {
1172 result = SCAN_PAGE_LRU;
1175 if (PageLocked(page)) {
1176 result = SCAN_PAGE_LOCK;
1179 if (!PageAnon(page)) {
1180 result = SCAN_PAGE_ANON;
1185 * cannot use mapcount: can't collapse if there's a gup pin.
1186 * The page must only be referenced by the scanned process
1187 * and page swap cache.
1189 if (page_count(page) != 1 + !!PageSwapCache(page)) {
1190 result = SCAN_PAGE_COUNT;
1193 if (pte_young(pteval) ||
1194 page_is_young(page) || PageReferenced(page) ||
1195 mmu_notifier_test_young(vma->vm_mm, address))
1200 result = SCAN_SUCCEED;
1203 result = SCAN_LACK_REFERENCED_PAGE;
1206 result = SCAN_PAGE_RO;
1209 pte_unmap_unlock(pte, ptl);
1211 node = khugepaged_find_target_node();
1212 /* collapse_huge_page will return with the mmap_sem released */
1213 collapse_huge_page(mm, address, hpage, node, referenced);
1216 trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,
1217 none_or_zero, result, unmapped);
1221 static void collect_mm_slot(struct mm_slot *mm_slot)
1223 struct mm_struct *mm = mm_slot->mm;
1225 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
1227 if (khugepaged_test_exit(mm)) {
1229 hash_del(&mm_slot->hash);
1230 list_del(&mm_slot->mm_node);
1233 * Not strictly needed because the mm exited already.
1235 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1238 /* khugepaged_mm_lock actually not necessary for the below */
1239 free_mm_slot(mm_slot);
1244 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
1245 static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)
1247 struct vm_area_struct *vma;
1251 i_mmap_lock_write(mapping);
1252 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
1253 /* probably overkill */
1256 addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
1257 if (addr & ~HPAGE_PMD_MASK)
1259 if (vma->vm_end < addr + HPAGE_PMD_SIZE)
1261 pmd = mm_find_pmd(vma->vm_mm, addr);
1265 * We need exclusive mmap_sem to retract page table.
1266 * If trylock fails we would end up with pte-mapped THP after
1267 * re-fault. Not ideal, but it's more important to not disturb
1268 * the system too much.
1270 if (down_write_trylock(&vma->vm_mm->mmap_sem)) {
1271 spinlock_t *ptl = pmd_lock(vma->vm_mm, pmd);
1272 /* assume page table is clear */
1273 _pmd = pmdp_collapse_flush(vma, addr, pmd);
1275 up_write(&vma->vm_mm->mmap_sem);
1276 atomic_long_dec(&vma->vm_mm->nr_ptes);
1277 pte_free(vma->vm_mm, pmd_pgtable(_pmd));
1280 i_mmap_unlock_write(mapping);
1284 * collapse_shmem - collapse small tmpfs/shmem pages into huge one.
1286 * Basic scheme is simple, details are more complex:
1287 * - allocate and freeze a new huge page;
1288 * - scan over radix tree replacing old pages the new one
1289 * + swap in pages if necessary;
1291 * + keep old pages around in case if rollback is required;
1292 * - if replacing succeed:
1295 * + unfreeze huge page;
1296 * - if replacing failed;
1297 * + put all pages back and unfreeze them;
1298 * + restore gaps in the radix-tree;
1301 static void collapse_shmem(struct mm_struct *mm,
1302 struct address_space *mapping, pgoff_t start,
1303 struct page **hpage, int node)
1306 struct page *page, *new_page, *tmp;
1307 struct mem_cgroup *memcg;
1308 pgoff_t index, end = start + HPAGE_PMD_NR;
1309 LIST_HEAD(pagelist);
1310 struct radix_tree_iter iter;
1312 int nr_none = 0, result = SCAN_SUCCEED;
1314 VM_BUG_ON(start & (HPAGE_PMD_NR - 1));
1316 /* Only allocate from the target node */
1317 gfp = alloc_hugepage_khugepaged_gfpmask() |
1318 __GFP_OTHER_NODE | __GFP_THISNODE;
1320 new_page = khugepaged_alloc_page(hpage, gfp, node);
1322 result = SCAN_ALLOC_HUGE_PAGE_FAIL;
1326 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
1327 result = SCAN_CGROUP_CHARGE_FAIL;
1331 new_page->index = start;
1332 new_page->mapping = mapping;
1333 __SetPageSwapBacked(new_page);
1334 __SetPageLocked(new_page);
1335 BUG_ON(!page_ref_freeze(new_page, 1));
1339 * At this point the new_page is 'frozen' (page_count() is zero), locked
1340 * and not up-to-date. It's safe to insert it into radix tree, because
1341 * nobody would be able to map it or use it in other way until we
1346 spin_lock_irq(&mapping->tree_lock);
1347 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
1348 int n = min(iter.index, end) - index;
1351 * Handle holes in the radix tree: charge it from shmem and
1352 * insert relevant subpage of new_page into the radix-tree.
1354 if (n && !shmem_charge(mapping->host, n)) {
1359 for (; index < min(iter.index, end); index++) {
1360 radix_tree_insert(&mapping->page_tree, index,
1361 new_page + (index % HPAGE_PMD_NR));
1368 page = radix_tree_deref_slot_protected(slot,
1369 &mapping->tree_lock);
1370 if (radix_tree_exceptional_entry(page) || !PageUptodate(page)) {
1371 spin_unlock_irq(&mapping->tree_lock);
1372 /* swap in or instantiate fallocated page */
1373 if (shmem_getpage(mapping->host, index, &page,
1378 spin_lock_irq(&mapping->tree_lock);
1379 } else if (trylock_page(page)) {
1382 result = SCAN_PAGE_LOCK;
1387 * The page must be locked, so we can drop the tree_lock
1388 * without racing with truncate.
1390 VM_BUG_ON_PAGE(!PageLocked(page), page);
1391 VM_BUG_ON_PAGE(!PageUptodate(page), page);
1392 VM_BUG_ON_PAGE(PageTransCompound(page), page);
1394 if (page_mapping(page) != mapping) {
1395 result = SCAN_TRUNCATED;
1398 spin_unlock_irq(&mapping->tree_lock);
1400 if (isolate_lru_page(page)) {
1401 result = SCAN_DEL_PAGE_LRU;
1402 goto out_isolate_failed;
1405 if (page_mapped(page))
1406 unmap_mapping_range(mapping, index << PAGE_SHIFT,
1409 spin_lock_irq(&mapping->tree_lock);
1411 slot = radix_tree_lookup_slot(&mapping->page_tree, index);
1412 VM_BUG_ON_PAGE(page != radix_tree_deref_slot_protected(slot,
1413 &mapping->tree_lock), page);
1414 VM_BUG_ON_PAGE(page_mapped(page), page);
1417 * The page is expected to have page_count() == 3:
1418 * - we hold a pin on it;
1419 * - one reference from radix tree;
1420 * - one from isolate_lru_page;
1422 if (!page_ref_freeze(page, 3)) {
1423 result = SCAN_PAGE_COUNT;
1428 * Add the page to the list to be able to undo the collapse if
1429 * something go wrong.
1431 list_add_tail(&page->lru, &pagelist);
1433 /* Finally, replace with the new page. */
1434 radix_tree_replace_slot(slot,
1435 new_page + (index % HPAGE_PMD_NR));
1437 slot = radix_tree_iter_next(&iter);
1441 spin_unlock_irq(&mapping->tree_lock);
1442 putback_lru_page(page);
1454 * Handle hole in radix tree at the end of the range.
1455 * This code only triggers if there's nothing in radix tree
1458 if (result == SCAN_SUCCEED && index < end) {
1459 int n = end - index;
1461 if (!shmem_charge(mapping->host, n)) {
1466 for (; index < end; index++) {
1467 radix_tree_insert(&mapping->page_tree, index,
1468 new_page + (index % HPAGE_PMD_NR));
1474 spin_unlock_irq(&mapping->tree_lock);
1477 if (result == SCAN_SUCCEED) {
1478 unsigned long flags;
1479 struct zone *zone = page_zone(new_page);
1482 * Replacing old pages with new one has succeed, now we need to
1483 * copy the content and free old pages.
1485 list_for_each_entry_safe(page, tmp, &pagelist, lru) {
1486 copy_highpage(new_page + (page->index % HPAGE_PMD_NR),
1488 list_del(&page->lru);
1490 page_ref_unfreeze(page, 1);
1491 page->mapping = NULL;
1492 ClearPageActive(page);
1493 ClearPageUnevictable(page);
1497 local_irq_save(flags);
1498 __inc_node_page_state(new_page, NR_SHMEM_THPS);
1500 __mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none);
1501 __mod_node_page_state(zone->zone_pgdat, NR_SHMEM, nr_none);
1503 local_irq_restore(flags);
1506 * Remove pte page tables, so we can re-faulti
1509 retract_page_tables(mapping, start);
1511 /* Everything is ready, let's unfreeze the new_page */
1512 set_page_dirty(new_page);
1513 SetPageUptodate(new_page);
1514 page_ref_unfreeze(new_page, HPAGE_PMD_NR);
1515 mem_cgroup_commit_charge(new_page, memcg, false, true);
1516 lru_cache_add_anon(new_page);
1517 unlock_page(new_page);
1521 /* Something went wrong: rollback changes to the radix-tree */
1522 shmem_uncharge(mapping->host, nr_none);
1523 spin_lock_irq(&mapping->tree_lock);
1524 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter,
1526 if (iter.index >= end)
1528 page = list_first_entry_or_null(&pagelist,
1530 if (!page || iter.index < page->index) {
1534 /* Put holes back where they were */
1535 radix_tree_delete(&mapping->page_tree,
1537 slot = radix_tree_iter_next(&iter);
1541 VM_BUG_ON_PAGE(page->index != iter.index, page);
1543 /* Unfreeze the page. */
1544 list_del(&page->lru);
1545 page_ref_unfreeze(page, 2);
1546 radix_tree_replace_slot(slot, page);
1547 spin_unlock_irq(&mapping->tree_lock);
1548 putback_lru_page(page);
1550 spin_lock_irq(&mapping->tree_lock);
1551 slot = radix_tree_iter_next(&iter);
1554 spin_unlock_irq(&mapping->tree_lock);
1556 /* Unfreeze new_page, caller would take care about freeing it */
1557 page_ref_unfreeze(new_page, 1);
1558 mem_cgroup_cancel_charge(new_page, memcg, true);
1559 unlock_page(new_page);
1560 new_page->mapping = NULL;
1563 VM_BUG_ON(!list_empty(&pagelist));
1564 /* TODO: tracepoints */
1567 static void khugepaged_scan_shmem(struct mm_struct *mm,
1568 struct address_space *mapping,
1569 pgoff_t start, struct page **hpage)
1571 struct page *page = NULL;
1572 struct radix_tree_iter iter;
1575 int node = NUMA_NO_NODE;
1576 int result = SCAN_SUCCEED;
1580 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
1582 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
1583 if (iter.index >= start + HPAGE_PMD_NR)
1586 page = radix_tree_deref_slot(slot);
1587 if (radix_tree_deref_retry(page)) {
1588 slot = radix_tree_iter_retry(&iter);
1592 if (radix_tree_exception(page)) {
1593 if (++swap > khugepaged_max_ptes_swap) {
1594 result = SCAN_EXCEED_SWAP_PTE;
1600 if (PageTransCompound(page)) {
1601 result = SCAN_PAGE_COMPOUND;
1605 node = page_to_nid(page);
1606 if (khugepaged_scan_abort(node)) {
1607 result = SCAN_SCAN_ABORT;
1610 khugepaged_node_load[node]++;
1612 if (!PageLRU(page)) {
1613 result = SCAN_PAGE_LRU;
1617 if (page_count(page) != 1 + page_mapcount(page)) {
1618 result = SCAN_PAGE_COUNT;
1623 * We probably should check if the page is referenced here, but
1624 * nobody would transfer pte_young() to PageReferenced() for us.
1625 * And rmap walk here is just too costly...
1630 if (need_resched()) {
1632 slot = radix_tree_iter_next(&iter);
1637 if (result == SCAN_SUCCEED) {
1638 if (present < HPAGE_PMD_NR - khugepaged_max_ptes_none) {
1639 result = SCAN_EXCEED_NONE_PTE;
1641 node = khugepaged_find_target_node();
1642 collapse_shmem(mm, mapping, start, hpage, node);
1646 /* TODO: tracepoints */
1649 static void khugepaged_scan_shmem(struct mm_struct *mm,
1650 struct address_space *mapping,
1651 pgoff_t start, struct page **hpage)
1657 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
1658 struct page **hpage)
1659 __releases(&khugepaged_mm_lock)
1660 __acquires(&khugepaged_mm_lock)
1662 struct mm_slot *mm_slot;
1663 struct mm_struct *mm;
1664 struct vm_area_struct *vma;
1668 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
1670 if (khugepaged_scan.mm_slot)
1671 mm_slot = khugepaged_scan.mm_slot;
1673 mm_slot = list_entry(khugepaged_scan.mm_head.next,
1674 struct mm_slot, mm_node);
1675 khugepaged_scan.address = 0;
1676 khugepaged_scan.mm_slot = mm_slot;
1678 spin_unlock(&khugepaged_mm_lock);
1681 down_read(&mm->mmap_sem);
1682 if (unlikely(khugepaged_test_exit(mm)))
1685 vma = find_vma(mm, khugepaged_scan.address);
1688 for (; vma; vma = vma->vm_next) {
1689 unsigned long hstart, hend;
1692 if (unlikely(khugepaged_test_exit(mm))) {
1696 if (!hugepage_vma_check(vma)) {
1701 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1702 hend = vma->vm_end & HPAGE_PMD_MASK;
1705 if (khugepaged_scan.address > hend)
1707 if (khugepaged_scan.address < hstart)
1708 khugepaged_scan.address = hstart;
1709 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
1711 while (khugepaged_scan.address < hend) {
1714 if (unlikely(khugepaged_test_exit(mm)))
1715 goto breakouterloop;
1717 VM_BUG_ON(khugepaged_scan.address < hstart ||
1718 khugepaged_scan.address + HPAGE_PMD_SIZE >
1720 if (shmem_file(vma->vm_file)) {
1722 pgoff_t pgoff = linear_page_index(vma,
1723 khugepaged_scan.address);
1724 if (!shmem_huge_enabled(vma))
1726 file = get_file(vma->vm_file);
1727 up_read(&mm->mmap_sem);
1729 khugepaged_scan_shmem(mm, file->f_mapping,
1733 ret = khugepaged_scan_pmd(mm, vma,
1734 khugepaged_scan.address,
1737 /* move to next address */
1738 khugepaged_scan.address += HPAGE_PMD_SIZE;
1739 progress += HPAGE_PMD_NR;
1741 /* we released mmap_sem so break loop */
1742 goto breakouterloop_mmap_sem;
1743 if (progress >= pages)
1744 goto breakouterloop;
1748 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
1749 breakouterloop_mmap_sem:
1751 spin_lock(&khugepaged_mm_lock);
1752 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
1754 * Release the current mm_slot if this mm is about to die, or
1755 * if we scanned all vmas of this mm.
1757 if (khugepaged_test_exit(mm) || !vma) {
1759 * Make sure that if mm_users is reaching zero while
1760 * khugepaged runs here, khugepaged_exit will find
1761 * mm_slot not pointing to the exiting mm.
1763 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
1764 khugepaged_scan.mm_slot = list_entry(
1765 mm_slot->mm_node.next,
1766 struct mm_slot, mm_node);
1767 khugepaged_scan.address = 0;
1769 khugepaged_scan.mm_slot = NULL;
1770 khugepaged_full_scans++;
1773 collect_mm_slot(mm_slot);
1779 static int khugepaged_has_work(void)
1781 return !list_empty(&khugepaged_scan.mm_head) &&
1782 khugepaged_enabled();
1785 static int khugepaged_wait_event(void)
1787 return !list_empty(&khugepaged_scan.mm_head) ||
1788 kthread_should_stop();
1791 static void khugepaged_do_scan(void)
1793 struct page *hpage = NULL;
1794 unsigned int progress = 0, pass_through_head = 0;
1795 unsigned int pages = khugepaged_pages_to_scan;
1798 barrier(); /* write khugepaged_pages_to_scan to local stack */
1800 while (progress < pages) {
1801 if (!khugepaged_prealloc_page(&hpage, &wait))
1806 if (unlikely(kthread_should_stop() || try_to_freeze()))
1809 spin_lock(&khugepaged_mm_lock);
1810 if (!khugepaged_scan.mm_slot)
1811 pass_through_head++;
1812 if (khugepaged_has_work() &&
1813 pass_through_head < 2)
1814 progress += khugepaged_scan_mm_slot(pages - progress,
1818 spin_unlock(&khugepaged_mm_lock);
1821 if (!IS_ERR_OR_NULL(hpage))
1825 static bool khugepaged_should_wakeup(void)
1827 return kthread_should_stop() ||
1828 time_after_eq(jiffies, khugepaged_sleep_expire);
1831 static void khugepaged_wait_work(void)
1833 if (khugepaged_has_work()) {
1834 const unsigned long scan_sleep_jiffies =
1835 msecs_to_jiffies(khugepaged_scan_sleep_millisecs);
1837 if (!scan_sleep_jiffies)
1840 khugepaged_sleep_expire = jiffies + scan_sleep_jiffies;
1841 wait_event_freezable_timeout(khugepaged_wait,
1842 khugepaged_should_wakeup(),
1843 scan_sleep_jiffies);
1847 if (khugepaged_enabled())
1848 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
1851 static int khugepaged(void *none)
1853 struct mm_slot *mm_slot;
1856 set_user_nice(current, MAX_NICE);
1858 while (!kthread_should_stop()) {
1859 khugepaged_do_scan();
1860 khugepaged_wait_work();
1863 spin_lock(&khugepaged_mm_lock);
1864 mm_slot = khugepaged_scan.mm_slot;
1865 khugepaged_scan.mm_slot = NULL;
1867 collect_mm_slot(mm_slot);
1868 spin_unlock(&khugepaged_mm_lock);
1872 static void set_recommended_min_free_kbytes(void)
1876 unsigned long recommended_min;
1878 for_each_populated_zone(zone)
1881 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */
1882 recommended_min = pageblock_nr_pages * nr_zones * 2;
1885 * Make sure that on average at least two pageblocks are almost free
1886 * of another type, one for a migratetype to fall back to and a
1887 * second to avoid subsequent fallbacks of other types There are 3
1888 * MIGRATE_TYPES we care about.
1890 recommended_min += pageblock_nr_pages * nr_zones *
1891 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
1893 /* don't ever allow to reserve more than 5% of the lowmem */
1894 recommended_min = min(recommended_min,
1895 (unsigned long) nr_free_buffer_pages() / 20);
1896 recommended_min <<= (PAGE_SHIFT-10);
1898 if (recommended_min > min_free_kbytes) {
1899 if (user_min_free_kbytes >= 0)
1900 pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n",
1901 min_free_kbytes, recommended_min);
1903 min_free_kbytes = recommended_min;
1905 setup_per_zone_wmarks();
1908 int start_stop_khugepaged(void)
1910 static struct task_struct *khugepaged_thread __read_mostly;
1911 static DEFINE_MUTEX(khugepaged_mutex);
1914 mutex_lock(&khugepaged_mutex);
1915 if (khugepaged_enabled()) {
1916 if (!khugepaged_thread)
1917 khugepaged_thread = kthread_run(khugepaged, NULL,
1919 if (IS_ERR(khugepaged_thread)) {
1920 pr_err("khugepaged: kthread_run(khugepaged) failed\n");
1921 err = PTR_ERR(khugepaged_thread);
1922 khugepaged_thread = NULL;
1926 if (!list_empty(&khugepaged_scan.mm_head))
1927 wake_up_interruptible(&khugepaged_wait);
1929 set_recommended_min_free_kbytes();
1930 } else if (khugepaged_thread) {
1931 kthread_stop(khugepaged_thread);
1932 khugepaged_thread = NULL;
1935 mutex_unlock(&khugepaged_mutex);