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_NO_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
),
106 static ssize_t
scan_sleep_millisecs_show(struct kobject
*kobj
,
107 struct kobj_attribute
*attr
,
110 return sprintf(buf
, "%u\n", khugepaged_scan_sleep_millisecs
);
113 static ssize_t
scan_sleep_millisecs_store(struct kobject
*kobj
,
114 struct kobj_attribute
*attr
,
115 const char *buf
, size_t count
)
120 err
= kstrtoul(buf
, 10, &msecs
);
121 if (err
|| msecs
> UINT_MAX
)
124 khugepaged_scan_sleep_millisecs
= msecs
;
125 khugepaged_sleep_expire
= 0;
126 wake_up_interruptible(&khugepaged_wait
);
130 static struct kobj_attribute scan_sleep_millisecs_attr
=
131 __ATTR(scan_sleep_millisecs
, 0644, scan_sleep_millisecs_show
,
132 scan_sleep_millisecs_store
);
134 static ssize_t
alloc_sleep_millisecs_show(struct kobject
*kobj
,
135 struct kobj_attribute
*attr
,
138 return sprintf(buf
, "%u\n", khugepaged_alloc_sleep_millisecs
);
141 static ssize_t
alloc_sleep_millisecs_store(struct kobject
*kobj
,
142 struct kobj_attribute
*attr
,
143 const char *buf
, size_t count
)
148 err
= kstrtoul(buf
, 10, &msecs
);
149 if (err
|| msecs
> UINT_MAX
)
152 khugepaged_alloc_sleep_millisecs
= msecs
;
153 khugepaged_sleep_expire
= 0;
154 wake_up_interruptible(&khugepaged_wait
);
158 static struct kobj_attribute alloc_sleep_millisecs_attr
=
159 __ATTR(alloc_sleep_millisecs
, 0644, alloc_sleep_millisecs_show
,
160 alloc_sleep_millisecs_store
);
162 static ssize_t
pages_to_scan_show(struct kobject
*kobj
,
163 struct kobj_attribute
*attr
,
166 return sprintf(buf
, "%u\n", khugepaged_pages_to_scan
);
168 static ssize_t
pages_to_scan_store(struct kobject
*kobj
,
169 struct kobj_attribute
*attr
,
170 const char *buf
, size_t count
)
175 err
= kstrtoul(buf
, 10, &pages
);
176 if (err
|| !pages
|| pages
> UINT_MAX
)
179 khugepaged_pages_to_scan
= pages
;
183 static struct kobj_attribute pages_to_scan_attr
=
184 __ATTR(pages_to_scan
, 0644, pages_to_scan_show
,
185 pages_to_scan_store
);
187 static ssize_t
pages_collapsed_show(struct kobject
*kobj
,
188 struct kobj_attribute
*attr
,
191 return sprintf(buf
, "%u\n", khugepaged_pages_collapsed
);
193 static struct kobj_attribute pages_collapsed_attr
=
194 __ATTR_RO(pages_collapsed
);
196 static ssize_t
full_scans_show(struct kobject
*kobj
,
197 struct kobj_attribute
*attr
,
200 return sprintf(buf
, "%u\n", khugepaged_full_scans
);
202 static struct kobj_attribute full_scans_attr
=
203 __ATTR_RO(full_scans
);
205 static ssize_t
khugepaged_defrag_show(struct kobject
*kobj
,
206 struct kobj_attribute
*attr
, char *buf
)
208 return single_hugepage_flag_show(kobj
, attr
, buf
,
209 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG
);
211 static ssize_t
khugepaged_defrag_store(struct kobject
*kobj
,
212 struct kobj_attribute
*attr
,
213 const char *buf
, size_t count
)
215 return single_hugepage_flag_store(kobj
, attr
, buf
, count
,
216 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG
);
218 static struct kobj_attribute khugepaged_defrag_attr
=
219 __ATTR(defrag
, 0644, khugepaged_defrag_show
,
220 khugepaged_defrag_store
);
223 * max_ptes_none controls if khugepaged should collapse hugepages over
224 * any unmapped ptes in turn potentially increasing the memory
225 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
226 * reduce the available free memory in the system as it
227 * runs. Increasing max_ptes_none will instead potentially reduce the
228 * free memory in the system during the khugepaged scan.
230 static ssize_t
khugepaged_max_ptes_none_show(struct kobject
*kobj
,
231 struct kobj_attribute
*attr
,
234 return sprintf(buf
, "%u\n", khugepaged_max_ptes_none
);
236 static ssize_t
khugepaged_max_ptes_none_store(struct kobject
*kobj
,
237 struct kobj_attribute
*attr
,
238 const char *buf
, size_t count
)
241 unsigned long max_ptes_none
;
243 err
= kstrtoul(buf
, 10, &max_ptes_none
);
244 if (err
|| max_ptes_none
> HPAGE_PMD_NR
-1)
247 khugepaged_max_ptes_none
= max_ptes_none
;
251 static struct kobj_attribute khugepaged_max_ptes_none_attr
=
252 __ATTR(max_ptes_none
, 0644, khugepaged_max_ptes_none_show
,
253 khugepaged_max_ptes_none_store
);
255 static ssize_t
khugepaged_max_ptes_swap_show(struct kobject
*kobj
,
256 struct kobj_attribute
*attr
,
259 return sprintf(buf
, "%u\n", khugepaged_max_ptes_swap
);
262 static ssize_t
khugepaged_max_ptes_swap_store(struct kobject
*kobj
,
263 struct kobj_attribute
*attr
,
264 const char *buf
, size_t count
)
267 unsigned long max_ptes_swap
;
269 err
= kstrtoul(buf
, 10, &max_ptes_swap
);
270 if (err
|| max_ptes_swap
> HPAGE_PMD_NR
-1)
273 khugepaged_max_ptes_swap
= max_ptes_swap
;
278 static struct kobj_attribute khugepaged_max_ptes_swap_attr
=
279 __ATTR(max_ptes_swap
, 0644, khugepaged_max_ptes_swap_show
,
280 khugepaged_max_ptes_swap_store
);
282 static struct attribute
*khugepaged_attr
[] = {
283 &khugepaged_defrag_attr
.attr
,
284 &khugepaged_max_ptes_none_attr
.attr
,
285 &pages_to_scan_attr
.attr
,
286 &pages_collapsed_attr
.attr
,
287 &full_scans_attr
.attr
,
288 &scan_sleep_millisecs_attr
.attr
,
289 &alloc_sleep_millisecs_attr
.attr
,
290 &khugepaged_max_ptes_swap_attr
.attr
,
294 struct attribute_group khugepaged_attr_group
= {
295 .attrs
= khugepaged_attr
,
296 .name
= "khugepaged",
299 #define VM_NO_KHUGEPAGED (VM_SPECIAL | VM_HUGETLB)
301 int hugepage_madvise(struct vm_area_struct
*vma
,
302 unsigned long *vm_flags
, int advice
)
308 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
309 * can't handle this properly after s390_enable_sie, so we simply
310 * ignore the madvise to prevent qemu from causing a SIGSEGV.
312 if (mm_has_pgste(vma
->vm_mm
))
315 *vm_flags
&= ~VM_NOHUGEPAGE
;
316 *vm_flags
|= VM_HUGEPAGE
;
318 * If the vma become good for khugepaged to scan,
319 * register it here without waiting a page fault that
320 * may not happen any time soon.
322 if (!(*vm_flags
& VM_NO_KHUGEPAGED
) &&
323 khugepaged_enter_vma_merge(vma
, *vm_flags
))
326 case MADV_NOHUGEPAGE
:
327 *vm_flags
&= ~VM_HUGEPAGE
;
328 *vm_flags
|= VM_NOHUGEPAGE
;
330 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
331 * this vma even if we leave the mm registered in khugepaged if
332 * it got registered before VM_NOHUGEPAGE was set.
340 int __init
khugepaged_init(void)
342 mm_slot_cache
= kmem_cache_create("khugepaged_mm_slot",
343 sizeof(struct mm_slot
),
344 __alignof__(struct mm_slot
), 0, NULL
);
348 khugepaged_pages_to_scan
= HPAGE_PMD_NR
* 8;
349 khugepaged_max_ptes_none
= HPAGE_PMD_NR
- 1;
350 khugepaged_max_ptes_swap
= HPAGE_PMD_NR
/ 8;
355 void __init
khugepaged_destroy(void)
357 kmem_cache_destroy(mm_slot_cache
);
360 static inline struct mm_slot
*alloc_mm_slot(void)
362 if (!mm_slot_cache
) /* initialization failed */
364 return kmem_cache_zalloc(mm_slot_cache
, GFP_KERNEL
);
367 static inline void free_mm_slot(struct mm_slot
*mm_slot
)
369 kmem_cache_free(mm_slot_cache
, mm_slot
);
372 static struct mm_slot
*get_mm_slot(struct mm_struct
*mm
)
374 struct mm_slot
*mm_slot
;
376 hash_for_each_possible(mm_slots_hash
, mm_slot
, hash
, (unsigned long)mm
)
377 if (mm
== mm_slot
->mm
)
383 static void insert_to_mm_slots_hash(struct mm_struct
*mm
,
384 struct mm_slot
*mm_slot
)
387 hash_add(mm_slots_hash
, &mm_slot
->hash
, (long)mm
);
390 static inline int khugepaged_test_exit(struct mm_struct
*mm
)
392 return atomic_read(&mm
->mm_users
) == 0;
395 int __khugepaged_enter(struct mm_struct
*mm
)
397 struct mm_slot
*mm_slot
;
400 mm_slot
= alloc_mm_slot();
404 /* __khugepaged_exit() must not run from under us */
405 VM_BUG_ON_MM(khugepaged_test_exit(mm
), mm
);
406 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE
, &mm
->flags
))) {
407 free_mm_slot(mm_slot
);
411 spin_lock(&khugepaged_mm_lock
);
412 insert_to_mm_slots_hash(mm
, mm_slot
);
414 * Insert just behind the scanning cursor, to let the area settle
417 wakeup
= list_empty(&khugepaged_scan
.mm_head
);
418 list_add_tail(&mm_slot
->mm_node
, &khugepaged_scan
.mm_head
);
419 spin_unlock(&khugepaged_mm_lock
);
421 atomic_inc(&mm
->mm_count
);
423 wake_up_interruptible(&khugepaged_wait
);
428 int khugepaged_enter_vma_merge(struct vm_area_struct
*vma
,
429 unsigned long vm_flags
)
431 unsigned long hstart
, hend
;
434 * Not yet faulted in so we will register later in the
435 * page fault if needed.
438 if (vma
->vm_ops
|| (vm_flags
& VM_NO_KHUGEPAGED
))
439 /* khugepaged not yet working on file or special mappings */
441 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
442 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
444 return khugepaged_enter(vma
, vm_flags
);
448 void __khugepaged_exit(struct mm_struct
*mm
)
450 struct mm_slot
*mm_slot
;
453 spin_lock(&khugepaged_mm_lock
);
454 mm_slot
= get_mm_slot(mm
);
455 if (mm_slot
&& khugepaged_scan
.mm_slot
!= mm_slot
) {
456 hash_del(&mm_slot
->hash
);
457 list_del(&mm_slot
->mm_node
);
460 spin_unlock(&khugepaged_mm_lock
);
463 clear_bit(MMF_VM_HUGEPAGE
, &mm
->flags
);
464 free_mm_slot(mm_slot
);
466 } else if (mm_slot
) {
468 * This is required to serialize against
469 * khugepaged_test_exit() (which is guaranteed to run
470 * under mmap sem read mode). Stop here (after we
471 * return all pagetables will be destroyed) until
472 * khugepaged has finished working on the pagetables
473 * under the mmap_sem.
475 down_write(&mm
->mmap_sem
);
476 up_write(&mm
->mmap_sem
);
480 static void release_pte_page(struct page
*page
)
482 /* 0 stands for page_is_file_cache(page) == false */
483 dec_zone_page_state(page
, NR_ISOLATED_ANON
+ 0);
485 putback_lru_page(page
);
488 static void release_pte_pages(pte_t
*pte
, pte_t
*_pte
)
490 while (--_pte
>= pte
) {
491 pte_t pteval
= *_pte
;
492 if (!pte_none(pteval
) && !is_zero_pfn(pte_pfn(pteval
)))
493 release_pte_page(pte_page(pteval
));
497 static int __collapse_huge_page_isolate(struct vm_area_struct
*vma
,
498 unsigned long address
,
501 struct page
*page
= NULL
;
503 int none_or_zero
= 0, result
= 0;
504 bool referenced
= false, writable
= false;
506 for (_pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
;
507 _pte
++, address
+= PAGE_SIZE
) {
508 pte_t pteval
= *_pte
;
509 if (pte_none(pteval
) || (pte_present(pteval
) &&
510 is_zero_pfn(pte_pfn(pteval
)))) {
511 if (!userfaultfd_armed(vma
) &&
512 ++none_or_zero
<= khugepaged_max_ptes_none
) {
515 result
= SCAN_EXCEED_NONE_PTE
;
519 if (!pte_present(pteval
)) {
520 result
= SCAN_PTE_NON_PRESENT
;
523 page
= vm_normal_page(vma
, address
, pteval
);
524 if (unlikely(!page
)) {
525 result
= SCAN_PAGE_NULL
;
529 VM_BUG_ON_PAGE(PageCompound(page
), page
);
530 VM_BUG_ON_PAGE(!PageAnon(page
), page
);
531 VM_BUG_ON_PAGE(!PageSwapBacked(page
), page
);
534 * We can do it before isolate_lru_page because the
535 * page can't be freed from under us. NOTE: PG_lock
536 * is needed to serialize against split_huge_page
537 * when invoked from the VM.
539 if (!trylock_page(page
)) {
540 result
= SCAN_PAGE_LOCK
;
545 * cannot use mapcount: can't collapse if there's a gup pin.
546 * The page must only be referenced by the scanned process
547 * and page swap cache.
549 if (page_count(page
) != 1 + !!PageSwapCache(page
)) {
551 result
= SCAN_PAGE_COUNT
;
554 if (pte_write(pteval
)) {
557 if (PageSwapCache(page
) &&
558 !reuse_swap_page(page
, NULL
)) {
560 result
= SCAN_SWAP_CACHE_PAGE
;
564 * Page is not in the swap cache. It can be collapsed
570 * Isolate the page to avoid collapsing an hugepage
571 * currently in use by the VM.
573 if (isolate_lru_page(page
)) {
575 result
= SCAN_DEL_PAGE_LRU
;
578 /* 0 stands for page_is_file_cache(page) == false */
579 inc_zone_page_state(page
, NR_ISOLATED_ANON
+ 0);
580 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
581 VM_BUG_ON_PAGE(PageLRU(page
), page
);
583 /* If there is no mapped pte young don't collapse the page */
584 if (pte_young(pteval
) ||
585 page_is_young(page
) || PageReferenced(page
) ||
586 mmu_notifier_test_young(vma
->vm_mm
, address
))
589 if (likely(writable
)) {
590 if (likely(referenced
)) {
591 result
= SCAN_SUCCEED
;
592 trace_mm_collapse_huge_page_isolate(page
, none_or_zero
,
593 referenced
, writable
, result
);
597 result
= SCAN_PAGE_RO
;
601 release_pte_pages(pte
, _pte
);
602 trace_mm_collapse_huge_page_isolate(page
, none_or_zero
,
603 referenced
, writable
, result
);
607 static void __collapse_huge_page_copy(pte_t
*pte
, struct page
*page
,
608 struct vm_area_struct
*vma
,
609 unsigned long address
,
613 for (_pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
; _pte
++) {
614 pte_t pteval
= *_pte
;
615 struct page
*src_page
;
617 if (pte_none(pteval
) || is_zero_pfn(pte_pfn(pteval
))) {
618 clear_user_highpage(page
, address
);
619 add_mm_counter(vma
->vm_mm
, MM_ANONPAGES
, 1);
620 if (is_zero_pfn(pte_pfn(pteval
))) {
622 * ptl mostly unnecessary.
626 * paravirt calls inside pte_clear here are
629 pte_clear(vma
->vm_mm
, address
, _pte
);
633 src_page
= pte_page(pteval
);
634 copy_user_highpage(page
, src_page
, address
, vma
);
635 VM_BUG_ON_PAGE(page_mapcount(src_page
) != 1, src_page
);
636 release_pte_page(src_page
);
638 * ptl mostly unnecessary, but preempt has to
639 * be disabled to update the per-cpu stats
640 * inside page_remove_rmap().
644 * paravirt calls inside pte_clear here are
647 pte_clear(vma
->vm_mm
, address
, _pte
);
648 page_remove_rmap(src_page
, false);
650 free_page_and_swap_cache(src_page
);
653 address
+= PAGE_SIZE
;
658 static void khugepaged_alloc_sleep(void)
662 add_wait_queue(&khugepaged_wait
, &wait
);
663 freezable_schedule_timeout_interruptible(
664 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs
));
665 remove_wait_queue(&khugepaged_wait
, &wait
);
668 static int khugepaged_node_load
[MAX_NUMNODES
];
670 static bool khugepaged_scan_abort(int nid
)
675 * If zone_reclaim_mode is disabled, then no extra effort is made to
676 * allocate memory locally.
678 if (!zone_reclaim_mode
)
681 /* If there is a count for this node already, it must be acceptable */
682 if (khugepaged_node_load
[nid
])
685 for (i
= 0; i
< MAX_NUMNODES
; i
++) {
686 if (!khugepaged_node_load
[i
])
688 if (node_distance(nid
, i
) > RECLAIM_DISTANCE
)
694 /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */
695 static inline gfp_t
alloc_hugepage_khugepaged_gfpmask(void)
697 return GFP_TRANSHUGE
| (khugepaged_defrag() ? __GFP_DIRECT_RECLAIM
: 0);
701 static int khugepaged_find_target_node(void)
703 static int last_khugepaged_target_node
= NUMA_NO_NODE
;
704 int nid
, target_node
= 0, max_value
= 0;
706 /* find first node with max normal pages hit */
707 for (nid
= 0; nid
< MAX_NUMNODES
; nid
++)
708 if (khugepaged_node_load
[nid
] > max_value
) {
709 max_value
= khugepaged_node_load
[nid
];
713 /* do some balance if several nodes have the same hit record */
714 if (target_node
<= last_khugepaged_target_node
)
715 for (nid
= last_khugepaged_target_node
+ 1; nid
< MAX_NUMNODES
;
717 if (max_value
== khugepaged_node_load
[nid
]) {
722 last_khugepaged_target_node
= target_node
;
726 static bool khugepaged_prealloc_page(struct page
**hpage
, bool *wait
)
728 if (IS_ERR(*hpage
)) {
734 khugepaged_alloc_sleep();
744 khugepaged_alloc_page(struct page
**hpage
, gfp_t gfp
, int node
)
746 VM_BUG_ON_PAGE(*hpage
, *hpage
);
748 *hpage
= __alloc_pages_node(node
, gfp
, HPAGE_PMD_ORDER
);
749 if (unlikely(!*hpage
)) {
750 count_vm_event(THP_COLLAPSE_ALLOC_FAILED
);
751 *hpage
= ERR_PTR(-ENOMEM
);
755 prep_transhuge_page(*hpage
);
756 count_vm_event(THP_COLLAPSE_ALLOC
);
760 static int khugepaged_find_target_node(void)
765 static inline struct page
*alloc_khugepaged_hugepage(void)
769 page
= alloc_pages(alloc_hugepage_khugepaged_gfpmask(),
772 prep_transhuge_page(page
);
776 static struct page
*khugepaged_alloc_hugepage(bool *wait
)
781 hpage
= alloc_khugepaged_hugepage();
783 count_vm_event(THP_COLLAPSE_ALLOC_FAILED
);
788 khugepaged_alloc_sleep();
790 count_vm_event(THP_COLLAPSE_ALLOC
);
791 } while (unlikely(!hpage
) && likely(khugepaged_enabled()));
796 static bool khugepaged_prealloc_page(struct page
**hpage
, bool *wait
)
799 *hpage
= khugepaged_alloc_hugepage(wait
);
801 if (unlikely(!*hpage
))
808 khugepaged_alloc_page(struct page
**hpage
, gfp_t gfp
, int node
)
816 static bool hugepage_vma_check(struct vm_area_struct
*vma
)
818 if ((!(vma
->vm_flags
& VM_HUGEPAGE
) && !khugepaged_always()) ||
819 (vma
->vm_flags
& VM_NOHUGEPAGE
))
821 if (shmem_file(vma
->vm_file
)) {
822 if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE
))
824 return IS_ALIGNED((vma
->vm_start
>> PAGE_SHIFT
) - vma
->vm_pgoff
,
827 if (!vma
->anon_vma
|| vma
->vm_ops
)
829 if (is_vma_temporary_stack(vma
))
831 return !(vma
->vm_flags
& VM_NO_KHUGEPAGED
);
835 * If mmap_sem temporarily dropped, revalidate vma
836 * before taking mmap_sem.
837 * Return 0 if succeeds, otherwise return none-zero
841 static int hugepage_vma_revalidate(struct mm_struct
*mm
, unsigned long address
)
843 struct vm_area_struct
*vma
;
844 unsigned long hstart
, hend
;
846 if (unlikely(khugepaged_test_exit(mm
)))
847 return SCAN_ANY_PROCESS
;
849 vma
= find_vma(mm
, address
);
851 return SCAN_VMA_NULL
;
853 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
854 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
855 if (address
< hstart
|| address
+ HPAGE_PMD_SIZE
> hend
)
856 return SCAN_ADDRESS_RANGE
;
857 if (!hugepage_vma_check(vma
))
858 return SCAN_VMA_CHECK
;
863 * Bring missing pages in from swap, to complete THP collapse.
864 * Only done if khugepaged_scan_pmd believes it is worthwhile.
866 * Called and returns without pte mapped or spinlocks held,
867 * but with mmap_sem held to protect against vma changes.
870 static bool __collapse_huge_page_swapin(struct mm_struct
*mm
,
871 struct vm_area_struct
*vma
,
872 unsigned long address
, pmd_t
*pmd
)
875 int swapped_in
= 0, ret
= 0;
876 struct fault_env fe
= {
879 .flags
= FAULT_FLAG_ALLOW_RETRY
,
883 fe
.pte
= pte_offset_map(pmd
, address
);
884 for (; fe
.address
< address
+ HPAGE_PMD_NR
*PAGE_SIZE
;
885 fe
.pte
++, fe
.address
+= PAGE_SIZE
) {
887 if (!is_swap_pte(pteval
))
890 ret
= do_swap_page(&fe
, pteval
);
891 /* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */
892 if (ret
& VM_FAULT_RETRY
) {
893 down_read(&mm
->mmap_sem
);
894 /* vma is no longer available, don't continue to swapin */
895 if (hugepage_vma_revalidate(mm
, address
))
897 /* check if the pmd is still valid */
898 if (mm_find_pmd(mm
, address
) != pmd
)
901 if (ret
& VM_FAULT_ERROR
) {
902 trace_mm_collapse_huge_page_swapin(mm
, swapped_in
, 0);
905 /* pte is unmapped now, we need to map it */
906 fe
.pte
= pte_offset_map(pmd
, fe
.address
);
910 trace_mm_collapse_huge_page_swapin(mm
, swapped_in
, 1);
914 static void collapse_huge_page(struct mm_struct
*mm
,
915 unsigned long address
,
917 struct vm_area_struct
*vma
,
923 struct page
*new_page
;
924 spinlock_t
*pmd_ptl
, *pte_ptl
;
925 int isolated
= 0, result
= 0;
926 struct mem_cgroup
*memcg
;
927 unsigned long mmun_start
; /* For mmu_notifiers */
928 unsigned long mmun_end
; /* For mmu_notifiers */
931 VM_BUG_ON(address
& ~HPAGE_PMD_MASK
);
933 /* Only allocate from the target node */
934 gfp
= alloc_hugepage_khugepaged_gfpmask() | __GFP_OTHER_NODE
| __GFP_THISNODE
;
937 * Before allocating the hugepage, release the mmap_sem read lock.
938 * The allocation can take potentially a long time if it involves
939 * sync compaction, and we do not need to hold the mmap_sem during
940 * that. We will recheck the vma after taking it again in write mode.
942 up_read(&mm
->mmap_sem
);
943 new_page
= khugepaged_alloc_page(hpage
, gfp
, node
);
945 result
= SCAN_ALLOC_HUGE_PAGE_FAIL
;
949 if (unlikely(mem_cgroup_try_charge(new_page
, mm
, gfp
, &memcg
, true))) {
950 result
= SCAN_CGROUP_CHARGE_FAIL
;
954 down_read(&mm
->mmap_sem
);
955 result
= hugepage_vma_revalidate(mm
, address
);
957 mem_cgroup_cancel_charge(new_page
, memcg
, true);
958 up_read(&mm
->mmap_sem
);
962 pmd
= mm_find_pmd(mm
, address
);
964 result
= SCAN_PMD_NULL
;
965 mem_cgroup_cancel_charge(new_page
, memcg
, true);
966 up_read(&mm
->mmap_sem
);
971 * __collapse_huge_page_swapin always returns with mmap_sem locked.
972 * If it fails, release mmap_sem and jump directly out.
973 * Continuing to collapse causes inconsistency.
975 if (!__collapse_huge_page_swapin(mm
, vma
, address
, pmd
)) {
976 mem_cgroup_cancel_charge(new_page
, memcg
, true);
977 up_read(&mm
->mmap_sem
);
981 up_read(&mm
->mmap_sem
);
983 * Prevent all access to pagetables with the exception of
984 * gup_fast later handled by the ptep_clear_flush and the VM
985 * handled by the anon_vma lock + PG_lock.
987 down_write(&mm
->mmap_sem
);
988 result
= hugepage_vma_revalidate(mm
, address
);
991 /* check if the pmd is still valid */
992 if (mm_find_pmd(mm
, address
) != pmd
)
995 anon_vma_lock_write(vma
->anon_vma
);
997 pte
= pte_offset_map(pmd
, address
);
998 pte_ptl
= pte_lockptr(mm
, pmd
);
1000 mmun_start
= address
;
1001 mmun_end
= address
+ HPAGE_PMD_SIZE
;
1002 mmu_notifier_invalidate_range_start(mm
, mmun_start
, mmun_end
);
1003 pmd_ptl
= pmd_lock(mm
, pmd
); /* probably unnecessary */
1005 * After this gup_fast can't run anymore. This also removes
1006 * any huge TLB entry from the CPU so we won't allow
1007 * huge and small TLB entries for the same virtual address
1008 * to avoid the risk of CPU bugs in that area.
1010 _pmd
= pmdp_collapse_flush(vma
, address
, pmd
);
1011 spin_unlock(pmd_ptl
);
1012 mmu_notifier_invalidate_range_end(mm
, mmun_start
, mmun_end
);
1015 isolated
= __collapse_huge_page_isolate(vma
, address
, pte
);
1016 spin_unlock(pte_ptl
);
1018 if (unlikely(!isolated
)) {
1021 BUG_ON(!pmd_none(*pmd
));
1023 * We can only use set_pmd_at when establishing
1024 * hugepmds and never for establishing regular pmds that
1025 * points to regular pagetables. Use pmd_populate for that
1027 pmd_populate(mm
, pmd
, pmd_pgtable(_pmd
));
1028 spin_unlock(pmd_ptl
);
1029 anon_vma_unlock_write(vma
->anon_vma
);
1035 * All pages are isolated and locked so anon_vma rmap
1036 * can't run anymore.
1038 anon_vma_unlock_write(vma
->anon_vma
);
1040 __collapse_huge_page_copy(pte
, new_page
, vma
, address
, pte_ptl
);
1042 __SetPageUptodate(new_page
);
1043 pgtable
= pmd_pgtable(_pmd
);
1045 _pmd
= mk_huge_pmd(new_page
, vma
->vm_page_prot
);
1046 _pmd
= maybe_pmd_mkwrite(pmd_mkdirty(_pmd
), vma
);
1049 * spin_lock() below is not the equivalent of smp_wmb(), so
1050 * this is needed to avoid the copy_huge_page writes to become
1051 * visible after the set_pmd_at() write.
1056 BUG_ON(!pmd_none(*pmd
));
1057 page_add_new_anon_rmap(new_page
, vma
, address
, true);
1058 mem_cgroup_commit_charge(new_page
, memcg
, false, true);
1059 lru_cache_add_active_or_unevictable(new_page
, vma
);
1060 pgtable_trans_huge_deposit(mm
, pmd
, pgtable
);
1061 set_pmd_at(mm
, address
, pmd
, _pmd
);
1062 update_mmu_cache_pmd(vma
, address
, pmd
);
1063 spin_unlock(pmd_ptl
);
1067 khugepaged_pages_collapsed
++;
1068 result
= SCAN_SUCCEED
;
1070 up_write(&mm
->mmap_sem
);
1072 trace_mm_collapse_huge_page(mm
, isolated
, result
);
1075 mem_cgroup_cancel_charge(new_page
, memcg
, true);
1079 static int khugepaged_scan_pmd(struct mm_struct
*mm
,
1080 struct vm_area_struct
*vma
,
1081 unsigned long address
,
1082 struct page
**hpage
)
1086 int ret
= 0, none_or_zero
= 0, result
= 0;
1087 struct page
*page
= NULL
;
1088 unsigned long _address
;
1090 int node
= NUMA_NO_NODE
, unmapped
= 0;
1091 bool writable
= false, referenced
= false;
1093 VM_BUG_ON(address
& ~HPAGE_PMD_MASK
);
1095 pmd
= mm_find_pmd(mm
, address
);
1097 result
= SCAN_PMD_NULL
;
1101 memset(khugepaged_node_load
, 0, sizeof(khugepaged_node_load
));
1102 pte
= pte_offset_map_lock(mm
, pmd
, address
, &ptl
);
1103 for (_address
= address
, _pte
= pte
; _pte
< pte
+HPAGE_PMD_NR
;
1104 _pte
++, _address
+= PAGE_SIZE
) {
1105 pte_t pteval
= *_pte
;
1106 if (is_swap_pte(pteval
)) {
1107 if (++unmapped
<= khugepaged_max_ptes_swap
) {
1110 result
= SCAN_EXCEED_SWAP_PTE
;
1114 if (pte_none(pteval
) || is_zero_pfn(pte_pfn(pteval
))) {
1115 if (!userfaultfd_armed(vma
) &&
1116 ++none_or_zero
<= khugepaged_max_ptes_none
) {
1119 result
= SCAN_EXCEED_NONE_PTE
;
1123 if (!pte_present(pteval
)) {
1124 result
= SCAN_PTE_NON_PRESENT
;
1127 if (pte_write(pteval
))
1130 page
= vm_normal_page(vma
, _address
, pteval
);
1131 if (unlikely(!page
)) {
1132 result
= SCAN_PAGE_NULL
;
1136 /* TODO: teach khugepaged to collapse THP mapped with pte */
1137 if (PageCompound(page
)) {
1138 result
= SCAN_PAGE_COMPOUND
;
1143 * Record which node the original page is from and save this
1144 * information to khugepaged_node_load[].
1145 * Khupaged will allocate hugepage from the node has the max
1148 node
= page_to_nid(page
);
1149 if (khugepaged_scan_abort(node
)) {
1150 result
= SCAN_SCAN_ABORT
;
1153 khugepaged_node_load
[node
]++;
1154 if (!PageLRU(page
)) {
1155 result
= SCAN_PAGE_LRU
;
1158 if (PageLocked(page
)) {
1159 result
= SCAN_PAGE_LOCK
;
1162 if (!PageAnon(page
)) {
1163 result
= SCAN_PAGE_ANON
;
1168 * cannot use mapcount: can't collapse if there's a gup pin.
1169 * The page must only be referenced by the scanned process
1170 * and page swap cache.
1172 if (page_count(page
) != 1 + !!PageSwapCache(page
)) {
1173 result
= SCAN_PAGE_COUNT
;
1176 if (pte_young(pteval
) ||
1177 page_is_young(page
) || PageReferenced(page
) ||
1178 mmu_notifier_test_young(vma
->vm_mm
, address
))
1183 result
= SCAN_SUCCEED
;
1186 result
= SCAN_NO_REFERENCED_PAGE
;
1189 result
= SCAN_PAGE_RO
;
1192 pte_unmap_unlock(pte
, ptl
);
1194 node
= khugepaged_find_target_node();
1195 /* collapse_huge_page will return with the mmap_sem released */
1196 collapse_huge_page(mm
, address
, hpage
, vma
, node
);
1199 trace_mm_khugepaged_scan_pmd(mm
, page
, writable
, referenced
,
1200 none_or_zero
, result
, unmapped
);
1204 static void collect_mm_slot(struct mm_slot
*mm_slot
)
1206 struct mm_struct
*mm
= mm_slot
->mm
;
1208 VM_BUG_ON(NR_CPUS
!= 1 && !spin_is_locked(&khugepaged_mm_lock
));
1210 if (khugepaged_test_exit(mm
)) {
1212 hash_del(&mm_slot
->hash
);
1213 list_del(&mm_slot
->mm_node
);
1216 * Not strictly needed because the mm exited already.
1218 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1221 /* khugepaged_mm_lock actually not necessary for the below */
1222 free_mm_slot(mm_slot
);
1227 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
1228 static void retract_page_tables(struct address_space
*mapping
, pgoff_t pgoff
)
1230 struct vm_area_struct
*vma
;
1234 i_mmap_lock_write(mapping
);
1235 vma_interval_tree_foreach(vma
, &mapping
->i_mmap
, pgoff
, pgoff
) {
1236 /* probably overkill */
1239 addr
= vma
->vm_start
+ ((pgoff
- vma
->vm_pgoff
) << PAGE_SHIFT
);
1240 if (addr
& ~HPAGE_PMD_MASK
)
1242 if (vma
->vm_end
< addr
+ HPAGE_PMD_SIZE
)
1244 pmd
= mm_find_pmd(vma
->vm_mm
, addr
);
1248 * We need exclusive mmap_sem to retract page table.
1249 * If trylock fails we would end up with pte-mapped THP after
1250 * re-fault. Not ideal, but it's more important to not disturb
1251 * the system too much.
1253 if (down_write_trylock(&vma
->vm_mm
->mmap_sem
)) {
1254 spinlock_t
*ptl
= pmd_lock(vma
->vm_mm
, pmd
);
1255 /* assume page table is clear */
1256 _pmd
= pmdp_collapse_flush(vma
, addr
, pmd
);
1258 up_write(&vma
->vm_mm
->mmap_sem
);
1259 atomic_long_dec(&vma
->vm_mm
->nr_ptes
);
1260 pte_free(vma
->vm_mm
, pmd_pgtable(_pmd
));
1263 i_mmap_unlock_write(mapping
);
1267 * collapse_shmem - collapse small tmpfs/shmem pages into huge one.
1269 * Basic scheme is simple, details are more complex:
1270 * - allocate and freeze a new huge page;
1271 * - scan over radix tree replacing old pages the new one
1272 * + swap in pages if necessary;
1274 * + keep old pages around in case if rollback is required;
1275 * - if replacing succeed:
1278 * + unfreeze huge page;
1279 * - if replacing failed;
1280 * + put all pages back and unfreeze them;
1281 * + restore gaps in the radix-tree;
1284 static void collapse_shmem(struct mm_struct
*mm
,
1285 struct address_space
*mapping
, pgoff_t start
,
1286 struct page
**hpage
, int node
)
1289 struct page
*page
, *new_page
, *tmp
;
1290 struct mem_cgroup
*memcg
;
1291 pgoff_t index
, end
= start
+ HPAGE_PMD_NR
;
1292 LIST_HEAD(pagelist
);
1293 struct radix_tree_iter iter
;
1295 int nr_none
= 0, result
= SCAN_SUCCEED
;
1297 VM_BUG_ON(start
& (HPAGE_PMD_NR
- 1));
1299 /* Only allocate from the target node */
1300 gfp
= alloc_hugepage_khugepaged_gfpmask() |
1301 __GFP_OTHER_NODE
| __GFP_THISNODE
;
1303 new_page
= khugepaged_alloc_page(hpage
, gfp
, node
);
1305 result
= SCAN_ALLOC_HUGE_PAGE_FAIL
;
1309 if (unlikely(mem_cgroup_try_charge(new_page
, mm
, gfp
, &memcg
, true))) {
1310 result
= SCAN_CGROUP_CHARGE_FAIL
;
1314 new_page
->index
= start
;
1315 new_page
->mapping
= mapping
;
1316 __SetPageSwapBacked(new_page
);
1317 __SetPageLocked(new_page
);
1318 BUG_ON(!page_ref_freeze(new_page
, 1));
1322 * At this point the new_page is 'frozen' (page_count() is zero), locked
1323 * and not up-to-date. It's safe to insert it into radix tree, because
1324 * nobody would be able to map it or use it in other way until we
1329 spin_lock_irq(&mapping
->tree_lock
);
1330 radix_tree_for_each_slot(slot
, &mapping
->page_tree
, &iter
, start
) {
1331 int n
= min(iter
.index
, end
) - index
;
1334 * Handle holes in the radix tree: charge it from shmem and
1335 * insert relevant subpage of new_page into the radix-tree.
1337 if (n
&& !shmem_charge(mapping
->host
, n
)) {
1342 for (; index
< min(iter
.index
, end
); index
++) {
1343 radix_tree_insert(&mapping
->page_tree
, index
,
1344 new_page
+ (index
% HPAGE_PMD_NR
));
1351 page
= radix_tree_deref_slot_protected(slot
,
1352 &mapping
->tree_lock
);
1353 if (radix_tree_exceptional_entry(page
) || !PageUptodate(page
)) {
1354 spin_unlock_irq(&mapping
->tree_lock
);
1355 /* swap in or instantiate fallocated page */
1356 if (shmem_getpage(mapping
->host
, index
, &page
,
1361 spin_lock_irq(&mapping
->tree_lock
);
1362 } else if (trylock_page(page
)) {
1365 result
= SCAN_PAGE_LOCK
;
1370 * The page must be locked, so we can drop the tree_lock
1371 * without racing with truncate.
1373 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
1374 VM_BUG_ON_PAGE(!PageUptodate(page
), page
);
1375 VM_BUG_ON_PAGE(PageTransCompound(page
), page
);
1377 if (page_mapping(page
) != mapping
) {
1378 result
= SCAN_TRUNCATED
;
1381 spin_unlock_irq(&mapping
->tree_lock
);
1383 if (isolate_lru_page(page
)) {
1384 result
= SCAN_DEL_PAGE_LRU
;
1385 goto out_isolate_failed
;
1388 if (page_mapped(page
))
1389 unmap_mapping_range(mapping
, index
<< PAGE_SHIFT
,
1392 spin_lock_irq(&mapping
->tree_lock
);
1394 VM_BUG_ON_PAGE(page_mapped(page
), page
);
1397 * The page is expected to have page_count() == 3:
1398 * - we hold a pin on it;
1399 * - one reference from radix tree;
1400 * - one from isolate_lru_page;
1402 if (!page_ref_freeze(page
, 3)) {
1403 result
= SCAN_PAGE_COUNT
;
1408 * Add the page to the list to be able to undo the collapse if
1409 * something go wrong.
1411 list_add_tail(&page
->lru
, &pagelist
);
1413 /* Finally, replace with the new page. */
1414 radix_tree_replace_slot(slot
,
1415 new_page
+ (index
% HPAGE_PMD_NR
));
1420 spin_unlock_irq(&mapping
->tree_lock
);
1421 putback_lru_page(page
);
1433 * Handle hole in radix tree at the end of the range.
1434 * This code only triggers if there's nothing in radix tree
1437 if (result
== SCAN_SUCCEED
&& index
< end
) {
1438 int n
= end
- index
;
1440 if (!shmem_charge(mapping
->host
, n
)) {
1445 for (; index
< end
; index
++) {
1446 radix_tree_insert(&mapping
->page_tree
, index
,
1447 new_page
+ (index
% HPAGE_PMD_NR
));
1453 spin_unlock_irq(&mapping
->tree_lock
);
1456 if (result
== SCAN_SUCCEED
) {
1457 unsigned long flags
;
1458 struct zone
*zone
= page_zone(new_page
);
1461 * Replacing old pages with new one has succeed, now we need to
1462 * copy the content and free old pages.
1464 list_for_each_entry_safe(page
, tmp
, &pagelist
, lru
) {
1465 copy_highpage(new_page
+ (page
->index
% HPAGE_PMD_NR
),
1467 list_del(&page
->lru
);
1469 page_ref_unfreeze(page
, 1);
1470 page
->mapping
= NULL
;
1471 ClearPageActive(page
);
1472 ClearPageUnevictable(page
);
1476 local_irq_save(flags
);
1477 __inc_zone_page_state(new_page
, NR_SHMEM_THPS
);
1479 __mod_zone_page_state(zone
, NR_FILE_PAGES
, nr_none
);
1480 __mod_zone_page_state(zone
, NR_SHMEM
, nr_none
);
1482 local_irq_restore(flags
);
1485 * Remove pte page tables, so we can re-faulti
1488 retract_page_tables(mapping
, start
);
1490 /* Everything is ready, let's unfreeze the new_page */
1491 set_page_dirty(new_page
);
1492 SetPageUptodate(new_page
);
1493 page_ref_unfreeze(new_page
, HPAGE_PMD_NR
);
1494 mem_cgroup_commit_charge(new_page
, memcg
, false, true);
1495 lru_cache_add_anon(new_page
);
1496 unlock_page(new_page
);
1500 /* Something went wrong: rollback changes to the radix-tree */
1501 shmem_uncharge(mapping
->host
, nr_none
);
1502 spin_lock_irq(&mapping
->tree_lock
);
1503 radix_tree_for_each_slot(slot
, &mapping
->page_tree
, &iter
,
1505 if (iter
.index
>= end
)
1507 page
= list_first_entry_or_null(&pagelist
,
1509 if (!page
|| iter
.index
< page
->index
) {
1512 /* Put holes back where they were */
1513 radix_tree_replace_slot(slot
, NULL
);
1518 VM_BUG_ON_PAGE(page
->index
!= iter
.index
, page
);
1520 /* Unfreeze the page. */
1521 list_del(&page
->lru
);
1522 page_ref_unfreeze(page
, 2);
1523 radix_tree_replace_slot(slot
, page
);
1524 spin_unlock_irq(&mapping
->tree_lock
);
1525 putback_lru_page(page
);
1527 spin_lock_irq(&mapping
->tree_lock
);
1530 spin_unlock_irq(&mapping
->tree_lock
);
1532 /* Unfreeze new_page, caller would take care about freeing it */
1533 page_ref_unfreeze(new_page
, 1);
1534 mem_cgroup_cancel_charge(new_page
, memcg
, true);
1535 unlock_page(new_page
);
1536 new_page
->mapping
= NULL
;
1539 VM_BUG_ON(!list_empty(&pagelist
));
1540 /* TODO: tracepoints */
1543 static void khugepaged_scan_shmem(struct mm_struct
*mm
,
1544 struct address_space
*mapping
,
1545 pgoff_t start
, struct page
**hpage
)
1547 struct page
*page
= NULL
;
1548 struct radix_tree_iter iter
;
1551 int node
= NUMA_NO_NODE
;
1552 int result
= SCAN_SUCCEED
;
1556 memset(khugepaged_node_load
, 0, sizeof(khugepaged_node_load
));
1558 radix_tree_for_each_slot(slot
, &mapping
->page_tree
, &iter
, start
) {
1559 if (iter
.index
>= start
+ HPAGE_PMD_NR
)
1562 page
= radix_tree_deref_slot(slot
);
1563 if (radix_tree_deref_retry(page
)) {
1564 slot
= radix_tree_iter_retry(&iter
);
1568 if (radix_tree_exception(page
)) {
1569 if (++swap
> khugepaged_max_ptes_swap
) {
1570 result
= SCAN_EXCEED_SWAP_PTE
;
1576 if (PageTransCompound(page
)) {
1577 result
= SCAN_PAGE_COMPOUND
;
1581 node
= page_to_nid(page
);
1582 if (khugepaged_scan_abort(node
)) {
1583 result
= SCAN_SCAN_ABORT
;
1586 khugepaged_node_load
[node
]++;
1588 if (!PageLRU(page
)) {
1589 result
= SCAN_PAGE_LRU
;
1593 if (page_count(page
) != 1 + page_mapcount(page
)) {
1594 result
= SCAN_PAGE_COUNT
;
1599 * We probably should check if the page is referenced here, but
1600 * nobody would transfer pte_young() to PageReferenced() for us.
1601 * And rmap walk here is just too costly...
1606 if (need_resched()) {
1608 slot
= radix_tree_iter_next(&iter
);
1613 if (result
== SCAN_SUCCEED
) {
1614 if (present
< HPAGE_PMD_NR
- khugepaged_max_ptes_none
) {
1615 result
= SCAN_EXCEED_NONE_PTE
;
1617 node
= khugepaged_find_target_node();
1618 collapse_shmem(mm
, mapping
, start
, hpage
, node
);
1622 /* TODO: tracepoints */
1625 static void khugepaged_scan_shmem(struct mm_struct
*mm
,
1626 struct address_space
*mapping
,
1627 pgoff_t start
, struct page
**hpage
)
1633 static unsigned int khugepaged_scan_mm_slot(unsigned int pages
,
1634 struct page
**hpage
)
1635 __releases(&khugepaged_mm_lock
)
1636 __acquires(&khugepaged_mm_lock
)
1638 struct mm_slot
*mm_slot
;
1639 struct mm_struct
*mm
;
1640 struct vm_area_struct
*vma
;
1644 VM_BUG_ON(NR_CPUS
!= 1 && !spin_is_locked(&khugepaged_mm_lock
));
1646 if (khugepaged_scan
.mm_slot
)
1647 mm_slot
= khugepaged_scan
.mm_slot
;
1649 mm_slot
= list_entry(khugepaged_scan
.mm_head
.next
,
1650 struct mm_slot
, mm_node
);
1651 khugepaged_scan
.address
= 0;
1652 khugepaged_scan
.mm_slot
= mm_slot
;
1654 spin_unlock(&khugepaged_mm_lock
);
1657 down_read(&mm
->mmap_sem
);
1658 if (unlikely(khugepaged_test_exit(mm
)))
1661 vma
= find_vma(mm
, khugepaged_scan
.address
);
1664 for (; vma
; vma
= vma
->vm_next
) {
1665 unsigned long hstart
, hend
;
1668 if (unlikely(khugepaged_test_exit(mm
))) {
1672 if (!hugepage_vma_check(vma
)) {
1677 hstart
= (vma
->vm_start
+ ~HPAGE_PMD_MASK
) & HPAGE_PMD_MASK
;
1678 hend
= vma
->vm_end
& HPAGE_PMD_MASK
;
1681 if (khugepaged_scan
.address
> hend
)
1683 if (khugepaged_scan
.address
< hstart
)
1684 khugepaged_scan
.address
= hstart
;
1685 VM_BUG_ON(khugepaged_scan
.address
& ~HPAGE_PMD_MASK
);
1687 while (khugepaged_scan
.address
< hend
) {
1690 if (unlikely(khugepaged_test_exit(mm
)))
1691 goto breakouterloop
;
1693 VM_BUG_ON(khugepaged_scan
.address
< hstart
||
1694 khugepaged_scan
.address
+ HPAGE_PMD_SIZE
>
1696 if (shmem_file(vma
->vm_file
)) {
1698 pgoff_t pgoff
= linear_page_index(vma
,
1699 khugepaged_scan
.address
);
1700 if (!shmem_huge_enabled(vma
))
1702 file
= get_file(vma
->vm_file
);
1703 up_read(&mm
->mmap_sem
);
1705 khugepaged_scan_shmem(mm
, file
->f_mapping
,
1709 ret
= khugepaged_scan_pmd(mm
, vma
,
1710 khugepaged_scan
.address
,
1713 /* move to next address */
1714 khugepaged_scan
.address
+= HPAGE_PMD_SIZE
;
1715 progress
+= HPAGE_PMD_NR
;
1717 /* we released mmap_sem so break loop */
1718 goto breakouterloop_mmap_sem
;
1719 if (progress
>= pages
)
1720 goto breakouterloop
;
1724 up_read(&mm
->mmap_sem
); /* exit_mmap will destroy ptes after this */
1725 breakouterloop_mmap_sem
:
1727 spin_lock(&khugepaged_mm_lock
);
1728 VM_BUG_ON(khugepaged_scan
.mm_slot
!= mm_slot
);
1730 * Release the current mm_slot if this mm is about to die, or
1731 * if we scanned all vmas of this mm.
1733 if (khugepaged_test_exit(mm
) || !vma
) {
1735 * Make sure that if mm_users is reaching zero while
1736 * khugepaged runs here, khugepaged_exit will find
1737 * mm_slot not pointing to the exiting mm.
1739 if (mm_slot
->mm_node
.next
!= &khugepaged_scan
.mm_head
) {
1740 khugepaged_scan
.mm_slot
= list_entry(
1741 mm_slot
->mm_node
.next
,
1742 struct mm_slot
, mm_node
);
1743 khugepaged_scan
.address
= 0;
1745 khugepaged_scan
.mm_slot
= NULL
;
1746 khugepaged_full_scans
++;
1749 collect_mm_slot(mm_slot
);
1755 static int khugepaged_has_work(void)
1757 return !list_empty(&khugepaged_scan
.mm_head
) &&
1758 khugepaged_enabled();
1761 static int khugepaged_wait_event(void)
1763 return !list_empty(&khugepaged_scan
.mm_head
) ||
1764 kthread_should_stop();
1767 static void khugepaged_do_scan(void)
1769 struct page
*hpage
= NULL
;
1770 unsigned int progress
= 0, pass_through_head
= 0;
1771 unsigned int pages
= khugepaged_pages_to_scan
;
1774 barrier(); /* write khugepaged_pages_to_scan to local stack */
1776 while (progress
< pages
) {
1777 if (!khugepaged_prealloc_page(&hpage
, &wait
))
1782 if (unlikely(kthread_should_stop() || try_to_freeze()))
1785 spin_lock(&khugepaged_mm_lock
);
1786 if (!khugepaged_scan
.mm_slot
)
1787 pass_through_head
++;
1788 if (khugepaged_has_work() &&
1789 pass_through_head
< 2)
1790 progress
+= khugepaged_scan_mm_slot(pages
- progress
,
1794 spin_unlock(&khugepaged_mm_lock
);
1797 if (!IS_ERR_OR_NULL(hpage
))
1801 static bool khugepaged_should_wakeup(void)
1803 return kthread_should_stop() ||
1804 time_after_eq(jiffies
, khugepaged_sleep_expire
);
1807 static void khugepaged_wait_work(void)
1809 if (khugepaged_has_work()) {
1810 const unsigned long scan_sleep_jiffies
=
1811 msecs_to_jiffies(khugepaged_scan_sleep_millisecs
);
1813 if (!scan_sleep_jiffies
)
1816 khugepaged_sleep_expire
= jiffies
+ scan_sleep_jiffies
;
1817 wait_event_freezable_timeout(khugepaged_wait
,
1818 khugepaged_should_wakeup(),
1819 scan_sleep_jiffies
);
1823 if (khugepaged_enabled())
1824 wait_event_freezable(khugepaged_wait
, khugepaged_wait_event());
1827 static int khugepaged(void *none
)
1829 struct mm_slot
*mm_slot
;
1832 set_user_nice(current
, MAX_NICE
);
1834 while (!kthread_should_stop()) {
1835 khugepaged_do_scan();
1836 khugepaged_wait_work();
1839 spin_lock(&khugepaged_mm_lock
);
1840 mm_slot
= khugepaged_scan
.mm_slot
;
1841 khugepaged_scan
.mm_slot
= NULL
;
1843 collect_mm_slot(mm_slot
);
1844 spin_unlock(&khugepaged_mm_lock
);
1848 static void set_recommended_min_free_kbytes(void)
1852 unsigned long recommended_min
;
1854 for_each_populated_zone(zone
)
1857 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */
1858 recommended_min
= pageblock_nr_pages
* nr_zones
* 2;
1861 * Make sure that on average at least two pageblocks are almost free
1862 * of another type, one for a migratetype to fall back to and a
1863 * second to avoid subsequent fallbacks of other types There are 3
1864 * MIGRATE_TYPES we care about.
1866 recommended_min
+= pageblock_nr_pages
* nr_zones
*
1867 MIGRATE_PCPTYPES
* MIGRATE_PCPTYPES
;
1869 /* don't ever allow to reserve more than 5% of the lowmem */
1870 recommended_min
= min(recommended_min
,
1871 (unsigned long) nr_free_buffer_pages() / 20);
1872 recommended_min
<<= (PAGE_SHIFT
-10);
1874 if (recommended_min
> min_free_kbytes
) {
1875 if (user_min_free_kbytes
>= 0)
1876 pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n",
1877 min_free_kbytes
, recommended_min
);
1879 min_free_kbytes
= recommended_min
;
1881 setup_per_zone_wmarks();
1884 int start_stop_khugepaged(void)
1886 static struct task_struct
*khugepaged_thread __read_mostly
;
1887 static DEFINE_MUTEX(khugepaged_mutex
);
1890 mutex_lock(&khugepaged_mutex
);
1891 if (khugepaged_enabled()) {
1892 if (!khugepaged_thread
)
1893 khugepaged_thread
= kthread_run(khugepaged
, NULL
,
1895 if (IS_ERR(khugepaged_thread
)) {
1896 pr_err("khugepaged: kthread_run(khugepaged) failed\n");
1897 err
= PTR_ERR(khugepaged_thread
);
1898 khugepaged_thread
= NULL
;
1902 if (!list_empty(&khugepaged_scan
.mm_head
))
1903 wake_up_interruptible(&khugepaged_wait
);
1905 set_recommended_min_free_kbytes();
1906 } else if (khugepaged_thread
) {
1907 kthread_stop(khugepaged_thread
);
1908 khugepaged_thread
= NULL
;
1911 mutex_unlock(&khugepaged_mutex
);