2 * Copyright (c) 1991 Regents of the University of California.
5 * This code is derived from software contributed to Berkeley by
6 * The Mach Operating System project at Carnegie-Mellon University.
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 4. Neither the name of the University nor the names of its contributors
17 * may be used to endorse or promote products derived from this software
18 * without specific prior written permission.
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * from: @(#)vm_page.c 7.4 (Berkeley) 5/7/91
36 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
37 * All rights reserved.
39 * Authors: Avadis Tevanian, Jr., Michael Wayne Young
41 * Permission to use, copy, modify and distribute this software and
42 * its documentation is hereby granted, provided that both the copyright
43 * notice and this permission notice appear in all copies of the
44 * software, derivative works or modified versions, and any portions
45 * thereof, and that both notices appear in supporting documentation.
47 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
48 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
49 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
51 * Carnegie Mellon requests users of this software to return to
53 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
54 * School of Computer Science
55 * Carnegie Mellon University
56 * Pittsburgh PA 15213-3890
58 * any improvements or extensions that they make and grant Carnegie the
59 * rights to redistribute these changes.
63 * GENERAL RULES ON VM_PAGE MANIPULATION
65 * - a pageq mutex is required when adding or removing a page from a
66 * page queue (vm_page_queue[]), regardless of other mutexes or the
67 * busy state of a page.
69 * - a hash chain mutex is required when associating or disassociating
70 * a page from the VM PAGE CACHE hash table (vm_page_buckets),
71 * regardless of other mutexes or the busy state of a page.
73 * - either a hash chain mutex OR a busied page is required in order
74 * to modify the page flags. A hash chain mutex must be obtained in
75 * order to busy a page. A page's flags cannot be modified by a
76 * hash chain mutex if the page is marked busy.
78 * - The object memq mutex is held when inserting or removing
79 * pages from an object (vm_page_insert() or vm_page_remove()). This
80 * is different from the object's main mutex.
82 * Generally speaking, you have to be aware of side effects when running
83 * vm_page ops. A vm_page_lookup() will return with the hash chain
84 * locked, whether it was able to lookup the page or not. vm_page_free(),
85 * vm_page_cache(), vm_page_activate(), and a number of other routines
86 * will release the hash chain mutex for you. Intermediate manipulation
87 * routines such as vm_page_flag_set() expect the hash chain to be held
88 * on entry and the hash chain will remain held on return.
90 * pageq scanning can only occur with the pageq in question locked.
91 * We have a known bottleneck with the active queue, but the cache
92 * and free queues are actually arrays already.
96 * Resident memory management module.
99 #include <sys/cdefs.h>
100 __FBSDID("$FreeBSD$");
102 #include <sys/param.h>
103 #include <sys/systm.h>
104 #include <sys/lock.h>
105 #include <sys/malloc.h>
106 #include <sys/mutex.h>
107 #include <sys/proc.h>
108 #include <sys/vmmeter.h>
109 #include <sys/vnode.h>
112 #include <vm/vm_param.h>
113 #include <vm/vm_kern.h>
114 #include <vm/vm_object.h>
115 #include <vm/vm_page.h>
116 #include <vm/vm_pageout.h>
117 #include <vm/vm_pager.h>
118 #include <vm/vm_extern.h>
120 #include <vm/uma_int.h>
123 * Associated with page of user-allocatable memory is a
127 struct mtx vm_page_queue_mtx;
128 struct mtx vm_page_queue_free_mtx;
130 vm_page_t vm_page_array = 0;
131 int vm_page_array_size = 0;
133 int vm_page_zero_count = 0;
138 * Sets the page size, perhaps based upon the memory
139 * size. Must be called before any use of page-size
140 * dependent functions.
143 vm_set_page_size(void)
145 if (cnt.v_page_size == 0)
146 cnt.v_page_size = PAGE_SIZE;
147 if (((cnt.v_page_size - 1) & cnt.v_page_size) != 0)
148 panic("vm_set_page_size: page size not a power of two");
154 * Initializes the resident memory module.
156 * Allocates memory for the page cells, and
157 * for the object/offset-to-page hash table headers.
158 * Each page cell is initialized and placed on the free list.
161 vm_page_startup(vm_offset_t vaddr)
165 vm_paddr_t page_range;
172 /* the biggest memory array is the second group of pages */
174 vm_paddr_t biggestsize;
184 vaddr = round_page(vaddr);
186 for (i = 0; phys_avail[i + 1]; i += 2) {
187 phys_avail[i] = round_page(phys_avail[i]);
188 phys_avail[i + 1] = trunc_page(phys_avail[i + 1]);
191 for (i = 0; phys_avail[i + 1]; i += 2) {
192 vm_paddr_t size = phys_avail[i + 1] - phys_avail[i];
194 if (size > biggestsize) {
202 end = phys_avail[biggestone+1];
205 * Initialize the locks.
207 mtx_init(&vm_page_queue_mtx, "vm page queue mutex", NULL, MTX_DEF |
209 mtx_init(&vm_page_queue_free_mtx, "vm page queue free mutex", NULL,
213 * Initialize the queue headers for the free queue, the active queue
214 * and the inactive queue.
219 * Allocate memory for use when boot strapping the kernel memory
222 bootpages = UMA_BOOT_PAGES * UMA_SLAB_SIZE;
223 new_end = end - bootpages;
224 new_end = trunc_page(new_end);
225 mapped = pmap_map(&vaddr, new_end, end,
226 VM_PROT_READ | VM_PROT_WRITE);
227 bzero((caddr_t) mapped, end - new_end);
228 uma_startup((caddr_t)mapped);
231 * Compute the number of pages of memory that will be available for
232 * use (taking into account the overhead of a page structure per
235 first_page = phys_avail[0] / PAGE_SIZE;
236 page_range = phys_avail[(nblocks - 1) * 2 + 1] / PAGE_SIZE - first_page;
237 npages = (total - (page_range * sizeof(struct vm_page)) -
238 (end - new_end)) / PAGE_SIZE;
242 * Reserve an unmapped guard page to trap access to vm_page_array[-1].
247 * Initialize the mem entry structures now, and put them in the free
250 new_end = trunc_page(end - page_range * sizeof(struct vm_page));
251 mapped = pmap_map(&vaddr, new_end, end,
252 VM_PROT_READ | VM_PROT_WRITE);
253 vm_page_array = (vm_page_t) mapped;
254 phys_avail[biggestone + 1] = new_end;
257 * Clear all of the page structures
259 bzero((caddr_t) vm_page_array, page_range * sizeof(struct vm_page));
260 vm_page_array_size = page_range;
263 * Construct the free queue(s) in descending order (by physical
264 * address) so that the first 16MB of physical memory is allocated
265 * last rather than first. On large-memory machines, this avoids
266 * the exhaustion of low physical memory before isa_dma_init has run.
268 cnt.v_page_count = 0;
269 cnt.v_free_count = 0;
270 for (i = 0; phys_avail[i + 1] && npages > 0; i += 2) {
272 last_pa = phys_avail[i + 1];
273 while (pa < last_pa && npages-- > 0) {
274 vm_pageq_add_new_page(pa);
282 vm_page_flag_set(vm_page_t m, unsigned short bits)
285 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
290 vm_page_flag_clear(vm_page_t m, unsigned short bits)
293 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
298 vm_page_busy(vm_page_t m)
301 VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
302 KASSERT((m->flags & PG_BUSY) == 0,
303 ("vm_page_busy: page already busy!!!"));
304 vm_page_flag_set(m, PG_BUSY);
310 * wakeup anyone waiting for the page.
313 vm_page_flash(vm_page_t m)
315 if (m->flags & PG_WANTED) {
316 vm_page_flag_clear(m, PG_WANTED);
324 * clear the PG_BUSY flag and wakeup anyone waiting for the
329 vm_page_wakeup(vm_page_t m)
332 VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
333 KASSERT(m->flags & PG_BUSY, ("vm_page_wakeup: page not busy!!!"));
334 vm_page_flag_clear(m, PG_BUSY);
339 vm_page_io_start(vm_page_t m)
342 VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
343 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
348 vm_page_io_finish(vm_page_t m)
351 VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
352 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
359 * Keep page from being freed by the page daemon
360 * much of the same effect as wiring, except much lower
361 * overhead and should be used only for *very* temporary
362 * holding ("wiring").
365 vm_page_hold(vm_page_t mem)
368 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
373 vm_page_unhold(vm_page_t mem)
376 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
378 KASSERT(mem->hold_count >= 0, ("vm_page_unhold: hold count < 0!!!"));
379 if (mem->hold_count == 0 && mem->queue == PQ_HOLD)
380 vm_page_free_toq(mem);
388 * The clearing of PG_ZERO is a temporary safety until the code can be
389 * reviewed to determine that PG_ZERO is being properly cleared on
390 * write faults or maps. PG_ZERO was previously cleared in
394 vm_page_free(vm_page_t m)
396 vm_page_flag_clear(m, PG_ZERO);
398 vm_page_zero_idle_wakeup();
404 * Free a page to the zerod-pages queue
407 vm_page_free_zero(vm_page_t m)
409 vm_page_flag_set(m, PG_ZERO);
414 * vm_page_sleep_if_busy:
416 * Sleep and release the page queues lock if PG_BUSY is set or,
417 * if also_m_busy is TRUE, busy is non-zero. Returns TRUE if the
418 * thread slept and the page queues lock was released.
419 * Otherwise, retains the page queues lock and returns FALSE.
422 vm_page_sleep_if_busy(vm_page_t m, int also_m_busy, const char *msg)
425 int is_object_locked;
427 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
428 if ((m->flags & PG_BUSY) || (also_m_busy && m->busy)) {
429 vm_page_flag_set(m, PG_WANTED | PG_REFERENCED);
431 * It's possible that while we sleep, the page will get
432 * unbusied and freed. If we are holding the object
433 * lock, we will assume we hold a reference to the object
434 * such that even if m->object changes, we can re-lock
437 * Remove mtx_owned() after vm_object locking is finished.
440 if ((is_object_locked = object != NULL &&
441 mtx_owned(&object->mtx)))
442 mtx_unlock(&object->mtx);
443 msleep(m, &vm_page_queue_mtx, PDROP | PVM, msg, 0);
444 if (is_object_locked)
445 mtx_lock(&object->mtx);
454 * make page all dirty
457 vm_page_dirty(vm_page_t m)
459 KASSERT(m->queue - m->pc != PQ_CACHE,
460 ("vm_page_dirty: page in cache!"));
461 KASSERT(m->queue - m->pc != PQ_FREE,
462 ("vm_page_dirty: page is free!"));
463 m->dirty = VM_PAGE_BITS_ALL;
469 * Implements Sleator and Tarjan's top-down splay algorithm. Returns
470 * the vm_page containing the given pindex. If, however, that
471 * pindex is not found in the vm_object, returns a vm_page that is
472 * adjacent to the pindex, coming before or after it.
475 vm_page_splay(vm_pindex_t pindex, vm_page_t root)
477 struct vm_page dummy;
478 vm_page_t lefttreemax, righttreemin, y;
482 lefttreemax = righttreemin = &dummy;
484 if (pindex < root->pindex) {
485 if ((y = root->left) == NULL)
487 if (pindex < y->pindex) {
489 root->left = y->right;
492 if ((y = root->left) == NULL)
495 /* Link into the new root's right tree. */
496 righttreemin->left = root;
498 } else if (pindex > root->pindex) {
499 if ((y = root->right) == NULL)
501 if (pindex > y->pindex) {
503 root->right = y->left;
506 if ((y = root->right) == NULL)
509 /* Link into the new root's left tree. */
510 lefttreemax->right = root;
515 /* Assemble the new root. */
516 lefttreemax->right = root->left;
517 righttreemin->left = root->right;
518 root->left = dummy.right;
519 root->right = dummy.left;
524 * vm_page_insert: [ internal use only ]
526 * Inserts the given mem entry into the object and object list.
528 * The pagetables are not updated but will presumably fault the page
529 * in if necessary, or if a kernel page the caller will at some point
530 * enter the page into the kernel's pmap. We are not allowed to block
531 * here so we *can't* do this anyway.
533 * The object and page must be locked.
534 * This routine may not block.
537 vm_page_insert(vm_page_t m, vm_object_t object, vm_pindex_t pindex)
541 VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
542 if (m->object != NULL)
543 panic("vm_page_insert: page already inserted");
546 * Record the object/offset pair in this page
552 * Now link into the object's ordered list of backed pages.
558 TAILQ_INSERT_TAIL(&object->memq, m, listq);
560 root = vm_page_splay(pindex, root);
561 if (pindex < root->pindex) {
562 m->left = root->left;
565 TAILQ_INSERT_BEFORE(root, m, listq);
566 } else if (pindex == root->pindex)
567 panic("vm_page_insert: offset already allocated");
569 m->right = root->right;
572 TAILQ_INSERT_AFTER(&object->memq, root, m, listq);
576 object->generation++;
579 * show that the object has one more resident page.
581 object->resident_page_count++;
584 * Since we are inserting a new and possibly dirty page,
585 * update the object's OBJ_WRITEABLE and OBJ_MIGHTBEDIRTY flags.
587 if (m->flags & PG_WRITEABLE)
588 vm_object_set_writeable_dirty(object);
593 * NOTE: used by device pager as well -wfj
595 * Removes the given mem entry from the object/offset-page
596 * table and the object page list, but do not invalidate/terminate
599 * The object and page must be locked.
600 * The underlying pmap entry (if any) is NOT removed here.
601 * This routine may not block.
604 vm_page_remove(vm_page_t m)
609 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
610 if (m->object == NULL)
612 VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
613 if ((m->flags & PG_BUSY) == 0) {
614 panic("vm_page_remove: page not busy");
618 * Basically destroy the page.
625 * Now remove from the object's list of backed pages.
627 if (m != object->root)
628 vm_page_splay(m->pindex, object->root);
632 root = vm_page_splay(m->pindex, m->left);
633 root->right = m->right;
636 TAILQ_REMOVE(&object->memq, m, listq);
639 * And show that the object has one fewer resident page.
641 object->resident_page_count--;
642 object->generation++;
650 * Returns the page associated with the object/offset
651 * pair specified; if none is found, NULL is returned.
653 * The object must be locked.
654 * This routine may not block.
655 * This is a critical path routine
658 vm_page_lookup(vm_object_t object, vm_pindex_t pindex)
662 VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
663 if ((m = object->root) != NULL && m->pindex != pindex) {
664 m = vm_page_splay(pindex, m);
665 if ((object->root = m)->pindex != pindex)
674 * Move the given memory entry from its
675 * current object to the specified target object/offset.
677 * The object must be locked.
678 * This routine may not block.
680 * Note: swap associated with the page must be invalidated by the move. We
681 * have to do this for several reasons: (1) we aren't freeing the
682 * page, (2) we are dirtying the page, (3) the VM system is probably
683 * moving the page from object A to B, and will then later move
684 * the backing store from A to B and we can't have a conflict.
686 * Note: we *always* dirty the page. It is necessary both for the
687 * fact that we moved it, and because we may be invalidating
688 * swap. If the page is on the cache, we have to deactivate it
689 * or vm_page_dirty() will panic. Dirty pages are not allowed
693 vm_page_rename(vm_page_t m, vm_object_t new_object, vm_pindex_t new_pindex)
697 vm_page_insert(m, new_object, new_pindex);
698 if (m->queue - m->pc == PQ_CACHE)
699 vm_page_deactivate(m);
704 * vm_page_select_cache:
706 * Find a page on the cache queue with color optimization. As pages
707 * might be found, but not applicable, they are deactivated. This
708 * keeps us from using potentially busy cached pages.
710 * This routine may not block.
713 vm_page_select_cache(int color)
717 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
718 while ((m = vm_pageq_find(PQ_CACHE, color, FALSE)) != NULL) {
719 if ((m->flags & PG_BUSY) == 0 && m->busy == 0 &&
720 m->hold_count == 0 && (VM_OBJECT_TRYLOCK(m->object) ||
721 VM_OBJECT_LOCKED(m->object))) {
722 KASSERT(m->dirty == 0,
723 ("Found dirty cache page %p", m));
724 KASSERT(!pmap_page_is_mapped(m),
725 ("Found mapped cache page %p", m));
726 KASSERT((m->flags & PG_UNMANAGED) == 0,
727 ("Found unmanaged cache page %p", m));
728 KASSERT(m->wire_count == 0,
729 ("Found wired cache page %p", m));
732 vm_page_deactivate(m);
740 * Allocate and return a memory cell associated
741 * with this VM object/offset pair.
744 * VM_ALLOC_NORMAL normal process request
745 * VM_ALLOC_SYSTEM system *really* needs a page
746 * VM_ALLOC_INTERRUPT interrupt time request
747 * VM_ALLOC_ZERO zero page
749 * This routine may not block.
751 * Additional special handling is required when called from an
752 * interrupt (VM_ALLOC_INTERRUPT). We are not allowed to mess with
753 * the page cache in this case.
756 vm_page_alloc(vm_object_t object, vm_pindex_t pindex, int req)
758 vm_object_t m_object;
760 int color, flags, page_req;
762 page_req = req & VM_ALLOC_CLASS_MASK;
764 if ((req & VM_ALLOC_NOOBJ) == 0) {
765 KASSERT(object != NULL,
766 ("vm_page_alloc: NULL object."));
767 VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
768 color = (pindex + object->pg_color) & PQ_L2_MASK;
770 color = pindex & PQ_L2_MASK;
773 * The pager is allowed to eat deeper into the free page list.
775 if ((curproc == pageproc) && (page_req != VM_ALLOC_INTERRUPT)) {
776 page_req = VM_ALLOC_SYSTEM;
780 mtx_lock_spin(&vm_page_queue_free_mtx);
781 if (cnt.v_free_count > cnt.v_free_reserved ||
782 (page_req == VM_ALLOC_SYSTEM &&
783 cnt.v_cache_count == 0 &&
784 cnt.v_free_count > cnt.v_interrupt_free_min) ||
785 (page_req == VM_ALLOC_INTERRUPT && cnt.v_free_count > 0)) {
787 * Allocate from the free queue if the number of free pages
788 * exceeds the minimum for the request class.
790 m = vm_pageq_find(PQ_FREE, color, (req & VM_ALLOC_ZERO) != 0);
791 } else if (page_req != VM_ALLOC_INTERRUPT) {
792 mtx_unlock_spin(&vm_page_queue_free_mtx);
794 * Allocatable from cache (non-interrupt only). On success,
795 * we must free the page and try again, thus ensuring that
796 * cnt.v_*_free_min counters are replenished.
798 vm_page_lock_queues();
799 if ((m = vm_page_select_cache(color)) == NULL) {
800 #if defined(DIAGNOSTIC)
801 if (cnt.v_cache_count > 0)
802 printf("vm_page_alloc(NORMAL): missing pages on cache queue: %d\n", cnt.v_cache_count);
804 vm_page_unlock_queues();
805 atomic_add_int(&vm_pageout_deficit, 1);
809 m_object = m->object;
810 VM_OBJECT_LOCK_ASSERT(m_object, MA_OWNED);
813 vm_page_unlock_queues();
814 if (m_object != object)
815 VM_OBJECT_UNLOCK(m_object);
819 * Not allocatable from cache from interrupt, give up.
821 mtx_unlock_spin(&vm_page_queue_free_mtx);
822 atomic_add_int(&vm_pageout_deficit, 1);
828 * At this point we had better have found a good page.
833 ("vm_page_alloc(): missing page on free queue")
837 * Remove from free queue
839 vm_pageq_remove_nowakeup(m);
842 * Initialize structure. Only the PG_ZERO flag is inherited.
845 if (m->flags & PG_ZERO) {
846 vm_page_zero_count--;
847 if (req & VM_ALLOC_ZERO)
848 flags = PG_ZERO | PG_BUSY;
850 if (req & (VM_ALLOC_NOBUSY | VM_ALLOC_NOOBJ))
853 if (req & VM_ALLOC_WIRED) {
854 atomic_add_int(&cnt.v_wire_count, 1);
862 KASSERT(m->dirty == 0, ("vm_page_alloc: free/cache page %p was dirty", m));
863 mtx_unlock_spin(&vm_page_queue_free_mtx);
865 if ((req & VM_ALLOC_NOOBJ) == 0)
866 vm_page_insert(m, object, pindex);
871 * Don't wakeup too often - wakeup the pageout daemon when
872 * we would be nearly out of memory.
874 if (vm_paging_needed())
881 * vm_wait: (also see VM_WAIT macro)
883 * Block until free pages are available for allocation
884 * - Called in various places before memory allocations.
890 vm_page_lock_queues();
891 if (curproc == pageproc) {
892 vm_pageout_pages_needed = 1;
893 msleep(&vm_pageout_pages_needed, &vm_page_queue_mtx,
894 PDROP | PSWP, "VMWait", 0);
896 if (!vm_pages_needed) {
898 wakeup(&vm_pages_needed);
900 msleep(&cnt.v_free_count, &vm_page_queue_mtx, PDROP | PVM,
906 * vm_waitpfault: (also see VM_WAITPFAULT macro)
908 * Block until free pages are available for allocation
909 * - Called only in vm_fault so that processes page faulting
910 * can be easily tracked.
911 * - Sleeps at a lower priority than vm_wait() so that vm_wait()ing
912 * processes will be able to grab memory first. Do not change
913 * this balance without careful testing first.
919 vm_page_lock_queues();
920 if (!vm_pages_needed) {
922 wakeup(&vm_pages_needed);
924 msleep(&cnt.v_free_count, &vm_page_queue_mtx, PDROP | PUSER,
931 * Put the specified page on the active list (if appropriate).
932 * Ensure that act_count is at least ACT_INIT but do not otherwise
935 * The page queues must be locked.
936 * This routine may not block.
939 vm_page_activate(vm_page_t m)
942 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
943 if (m->queue != PQ_ACTIVE) {
944 if ((m->queue - m->pc) == PQ_CACHE)
947 if (m->wire_count == 0 && (m->flags & PG_UNMANAGED) == 0) {
948 if (m->act_count < ACT_INIT)
949 m->act_count = ACT_INIT;
950 vm_pageq_enqueue(PQ_ACTIVE, m);
953 if (m->act_count < ACT_INIT)
954 m->act_count = ACT_INIT;
959 * vm_page_free_wakeup:
961 * Helper routine for vm_page_free_toq() and vm_page_cache(). This
962 * routine is called when a page has been added to the cache or free
965 * The page queues must be locked.
966 * This routine may not block.
969 vm_page_free_wakeup(void)
972 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
974 * if pageout daemon needs pages, then tell it that there are
977 if (vm_pageout_pages_needed &&
978 cnt.v_cache_count + cnt.v_free_count >= cnt.v_pageout_free_min) {
979 wakeup(&vm_pageout_pages_needed);
980 vm_pageout_pages_needed = 0;
983 * wakeup processes that are waiting on memory if we hit a
984 * high water mark. And wakeup scheduler process if we have
985 * lots of memory. this process will swapin processes.
987 if (vm_pages_needed && !vm_page_count_min()) {
989 wakeup(&cnt.v_free_count);
996 * Returns the given page to the PQ_FREE list,
997 * disassociating it with any VM object.
999 * Object and page must be locked prior to entry.
1000 * This routine may not block.
1004 vm_page_free_toq(vm_page_t m)
1006 struct vpgqueues *pq;
1007 vm_object_t object = m->object;
1009 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
1012 if (m->busy || ((m->queue - m->pc) == PQ_FREE)) {
1014 "vm_page_free: pindex(%lu), busy(%d), PG_BUSY(%d), hold(%d)\n",
1015 (u_long)m->pindex, m->busy, (m->flags & PG_BUSY) ? 1 : 0,
1017 if ((m->queue - m->pc) == PQ_FREE)
1018 panic("vm_page_free: freeing free page");
1020 panic("vm_page_free: freeing busy page");
1024 * unqueue, then remove page. Note that we cannot destroy
1025 * the page here because we do not want to call the pager's
1026 * callback routine until after we've put the page on the
1027 * appropriate free queue.
1029 vm_pageq_remove_nowakeup(m);
1033 * If fictitious remove object association and
1034 * return, otherwise delay object association removal.
1036 if ((m->flags & PG_FICTITIOUS) != 0) {
1043 if (m->wire_count != 0) {
1044 if (m->wire_count > 1) {
1045 panic("vm_page_free: invalid wire count (%d), pindex: 0x%lx",
1046 m->wire_count, (long)m->pindex);
1048 panic("vm_page_free: freeing wired page");
1052 * If we've exhausted the object's resident pages we want to free
1056 (object->type == OBJT_VNODE) &&
1057 ((object->flags & OBJ_DEAD) == 0)
1059 struct vnode *vp = (struct vnode *)object->handle;
1063 if (VSHOULDFREE(vp))
1070 * Clear the UNMANAGED flag when freeing an unmanaged page.
1072 if (m->flags & PG_UNMANAGED) {
1073 m->flags &= ~PG_UNMANAGED;
1076 if (m->hold_count != 0) {
1077 m->flags &= ~PG_ZERO;
1080 m->queue = PQ_FREE + m->pc;
1081 pq = &vm_page_queues[m->queue];
1082 mtx_lock_spin(&vm_page_queue_free_mtx);
1087 * Put zero'd pages on the end ( where we look for zero'd pages
1088 * first ) and non-zerod pages at the head.
1090 if (m->flags & PG_ZERO) {
1091 TAILQ_INSERT_TAIL(&pq->pl, m, pageq);
1092 ++vm_page_zero_count;
1094 TAILQ_INSERT_HEAD(&pq->pl, m, pageq);
1096 mtx_unlock_spin(&vm_page_queue_free_mtx);
1097 vm_page_free_wakeup();
1103 * Prevent PV management from being done on the page. The page is
1104 * removed from the paging queues as if it were wired, and as a
1105 * consequence of no longer being managed the pageout daemon will not
1106 * touch it (since there is no way to locate the pte mappings for the
1107 * page). madvise() calls that mess with the pmap will also no longer
1108 * operate on the page.
1110 * Beyond that the page is still reasonably 'normal'. Freeing the page
1111 * will clear the flag.
1113 * This routine is used by OBJT_PHYS objects - objects using unswappable
1114 * physical memory as backing store rather then swap-backed memory and
1115 * will eventually be extended to support 4MB unmanaged physical
1119 vm_page_unmanage(vm_page_t m)
1122 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
1123 if ((m->flags & PG_UNMANAGED) == 0) {
1124 if (m->wire_count == 0)
1127 vm_page_flag_set(m, PG_UNMANAGED);
1133 * Mark this page as wired down by yet
1134 * another map, removing it from paging queues
1137 * The page queues must be locked.
1138 * This routine may not block.
1141 vm_page_wire(vm_page_t m)
1145 * Only bump the wire statistics if the page is not already wired,
1146 * and only unqueue the page if it is on some queue (if it is unmanaged
1147 * it is already off the queues).
1149 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
1150 if (m->flags & PG_FICTITIOUS)
1152 if (m->wire_count == 0) {
1153 if ((m->flags & PG_UNMANAGED) == 0)
1155 atomic_add_int(&cnt.v_wire_count, 1);
1158 KASSERT(m->wire_count != 0, ("vm_page_wire: wire_count overflow m=%p", m));
1164 * Release one wiring of this page, potentially
1165 * enabling it to be paged again.
1167 * Many pages placed on the inactive queue should actually go
1168 * into the cache, but it is difficult to figure out which. What
1169 * we do instead, if the inactive target is well met, is to put
1170 * clean pages at the head of the inactive queue instead of the tail.
1171 * This will cause them to be moved to the cache more quickly and
1172 * if not actively re-referenced, freed more quickly. If we just
1173 * stick these pages at the end of the inactive queue, heavy filesystem
1174 * meta-data accesses can cause an unnecessary paging load on memory bound
1175 * processes. This optimization causes one-time-use metadata to be
1176 * reused more quickly.
1178 * BUT, if we are in a low-memory situation we have no choice but to
1179 * put clean pages on the cache queue.
1181 * A number of routines use vm_page_unwire() to guarantee that the page
1182 * will go into either the inactive or active queues, and will NEVER
1183 * be placed in the cache - for example, just after dirtying a page.
1184 * dirty pages in the cache are not allowed.
1186 * The page queues must be locked.
1187 * This routine may not block.
1190 vm_page_unwire(vm_page_t m, int activate)
1193 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
1194 if (m->flags & PG_FICTITIOUS)
1196 if (m->wire_count > 0) {
1198 if (m->wire_count == 0) {
1199 atomic_subtract_int(&cnt.v_wire_count, 1);
1200 if (m->flags & PG_UNMANAGED) {
1202 } else if (activate)
1203 vm_pageq_enqueue(PQ_ACTIVE, m);
1205 vm_page_flag_clear(m, PG_WINATCFLS);
1206 vm_pageq_enqueue(PQ_INACTIVE, m);
1210 panic("vm_page_unwire: invalid wire count: %d", m->wire_count);
1216 * Move the specified page to the inactive queue. If the page has
1217 * any associated swap, the swap is deallocated.
1219 * Normally athead is 0 resulting in LRU operation. athead is set
1220 * to 1 if we want this page to be 'as if it were placed in the cache',
1221 * except without unmapping it from the process address space.
1223 * This routine may not block.
1225 static __inline void
1226 _vm_page_deactivate(vm_page_t m, int athead)
1229 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
1232 * Ignore if already inactive.
1234 if (m->queue == PQ_INACTIVE)
1236 if (m->wire_count == 0 && (m->flags & PG_UNMANAGED) == 0) {
1237 if ((m->queue - m->pc) == PQ_CACHE)
1238 cnt.v_reactivated++;
1239 vm_page_flag_clear(m, PG_WINATCFLS);
1242 TAILQ_INSERT_HEAD(&vm_page_queues[PQ_INACTIVE].pl, m, pageq);
1244 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_INACTIVE].pl, m, pageq);
1245 m->queue = PQ_INACTIVE;
1246 vm_page_queues[PQ_INACTIVE].lcnt++;
1247 cnt.v_inactive_count++;
1252 vm_page_deactivate(vm_page_t m)
1254 _vm_page_deactivate(m, 0);
1258 * vm_page_try_to_cache:
1260 * Returns 0 on failure, 1 on success
1263 vm_page_try_to_cache(vm_page_t m)
1266 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
1267 if (m->dirty || m->hold_count || m->busy || m->wire_count ||
1268 (m->flags & (PG_BUSY|PG_UNMANAGED))) {
1279 * vm_page_try_to_free()
1281 * Attempt to free the page. If we cannot free it, we do nothing.
1282 * 1 is returned on success, 0 on failure.
1285 vm_page_try_to_free(vm_page_t m)
1288 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
1289 if (m->object != NULL)
1290 VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
1291 if (m->dirty || m->hold_count || m->busy || m->wire_count ||
1292 (m->flags & (PG_BUSY|PG_UNMANAGED))) {
1306 * Put the specified page onto the page cache queue (if appropriate).
1308 * This routine may not block.
1311 vm_page_cache(vm_page_t m)
1314 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
1315 if ((m->flags & (PG_BUSY|PG_UNMANAGED)) || m->busy ||
1316 m->hold_count || m->wire_count) {
1317 printf("vm_page_cache: attempting to cache busy page\n");
1320 if ((m->queue - m->pc) == PQ_CACHE)
1324 * Remove all pmaps and indicate that the page is not
1325 * writeable or mapped.
1328 if (m->dirty != 0) {
1329 panic("vm_page_cache: caching a dirty page, pindex: %ld",
1332 vm_pageq_remove_nowakeup(m);
1333 vm_pageq_enqueue(PQ_CACHE + m->pc, m);
1334 vm_page_free_wakeup();
1340 * Cache, deactivate, or do nothing as appropriate. This routine
1341 * is typically used by madvise() MADV_DONTNEED.
1343 * Generally speaking we want to move the page into the cache so
1344 * it gets reused quickly. However, this can result in a silly syndrome
1345 * due to the page recycling too quickly. Small objects will not be
1346 * fully cached. On the otherhand, if we move the page to the inactive
1347 * queue we wind up with a problem whereby very large objects
1348 * unnecessarily blow away our inactive and cache queues.
1350 * The solution is to move the pages based on a fixed weighting. We
1351 * either leave them alone, deactivate them, or move them to the cache,
1352 * where moving them to the cache has the highest weighting.
1353 * By forcing some pages into other queues we eventually force the
1354 * system to balance the queues, potentially recovering other unrelated
1355 * space from active. The idea is to not force this to happen too
1359 vm_page_dontneed(vm_page_t m)
1361 static int dnweight;
1365 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
1369 * occassionally leave the page alone
1371 if ((dnw & 0x01F0) == 0 ||
1372 m->queue == PQ_INACTIVE ||
1373 m->queue - m->pc == PQ_CACHE
1375 if (m->act_count >= ACT_INIT)
1380 if (m->dirty == 0 && pmap_is_modified(m))
1383 if (m->dirty || (dnw & 0x0070) == 0) {
1385 * Deactivate the page 3 times out of 32.
1390 * Cache the page 28 times out of every 32. Note that
1391 * the page is deactivated instead of cached, but placed
1392 * at the head of the queue instead of the tail.
1396 _vm_page_deactivate(m, head);
1400 * Grab a page, waiting until we are waken up due to the page
1401 * changing state. We keep on waiting, if the page continues
1402 * to be in the object. If the page doesn't exist, first allocate it
1403 * and then conditionally zero it.
1405 * This routine may block.
1408 vm_page_grab(vm_object_t object, vm_pindex_t pindex, int allocflags)
1412 VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
1414 if ((m = vm_page_lookup(object, pindex)) != NULL) {
1415 vm_page_lock_queues();
1416 if (m->busy || (m->flags & PG_BUSY)) {
1417 vm_page_flag_set(m, PG_WANTED | PG_REFERENCED);
1418 VM_OBJECT_UNLOCK(object);
1419 msleep(m, &vm_page_queue_mtx, PDROP | PVM, "pgrbwt", 0);
1420 VM_OBJECT_LOCK(object);
1421 if ((allocflags & VM_ALLOC_RETRY) == 0)
1425 if (allocflags & VM_ALLOC_WIRED)
1427 if ((allocflags & VM_ALLOC_NOBUSY) == 0)
1429 vm_page_unlock_queues();
1433 m = vm_page_alloc(object, pindex, allocflags & ~VM_ALLOC_RETRY);
1435 VM_OBJECT_UNLOCK(object);
1437 VM_OBJECT_LOCK(object);
1438 if ((allocflags & VM_ALLOC_RETRY) == 0)
1442 if (allocflags & VM_ALLOC_ZERO && (m->flags & PG_ZERO) == 0)
1448 * Mapping function for valid bits or for dirty bits in
1449 * a page. May not block.
1451 * Inputs are required to range within a page.
1454 vm_page_bits(int base, int size)
1460 base + size <= PAGE_SIZE,
1461 ("vm_page_bits: illegal base/size %d/%d", base, size)
1464 if (size == 0) /* handle degenerate case */
1467 first_bit = base >> DEV_BSHIFT;
1468 last_bit = (base + size - 1) >> DEV_BSHIFT;
1470 return ((2 << last_bit) - (1 << first_bit));
1474 * vm_page_set_validclean:
1476 * Sets portions of a page valid and clean. The arguments are expected
1477 * to be DEV_BSIZE aligned but if they aren't the bitmap is inclusive
1478 * of any partial chunks touched by the range. The invalid portion of
1479 * such chunks will be zero'd.
1481 * This routine may not block.
1483 * (base + size) must be less then or equal to PAGE_SIZE.
1486 vm_page_set_validclean(vm_page_t m, int base, int size)
1492 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
1493 VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
1494 if (size == 0) /* handle degenerate case */
1498 * If the base is not DEV_BSIZE aligned and the valid
1499 * bit is clear, we have to zero out a portion of the
1502 if ((frag = base & ~(DEV_BSIZE - 1)) != base &&
1503 (m->valid & (1 << (base >> DEV_BSHIFT))) == 0)
1504 pmap_zero_page_area(m, frag, base - frag);
1507 * If the ending offset is not DEV_BSIZE aligned and the
1508 * valid bit is clear, we have to zero out a portion of
1511 endoff = base + size;
1512 if ((frag = endoff & ~(DEV_BSIZE - 1)) != endoff &&
1513 (m->valid & (1 << (endoff >> DEV_BSHIFT))) == 0)
1514 pmap_zero_page_area(m, endoff,
1515 DEV_BSIZE - (endoff & (DEV_BSIZE - 1)));
1518 * Set valid, clear dirty bits. If validating the entire
1519 * page we can safely clear the pmap modify bit. We also
1520 * use this opportunity to clear the PG_NOSYNC flag. If a process
1521 * takes a write fault on a MAP_NOSYNC memory area the flag will
1524 * We set valid bits inclusive of any overlap, but we can only
1525 * clear dirty bits for DEV_BSIZE chunks that are fully within
1528 pagebits = vm_page_bits(base, size);
1529 m->valid |= pagebits;
1531 if ((frag = base & (DEV_BSIZE - 1)) != 0) {
1532 frag = DEV_BSIZE - frag;
1538 pagebits = vm_page_bits(base, size & (DEV_BSIZE - 1));
1540 m->dirty &= ~pagebits;
1541 if (base == 0 && size == PAGE_SIZE) {
1542 pmap_clear_modify(m);
1543 vm_page_flag_clear(m, PG_NOSYNC);
1548 vm_page_clear_dirty(vm_page_t m, int base, int size)
1551 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
1552 m->dirty &= ~vm_page_bits(base, size);
1556 * vm_page_set_invalid:
1558 * Invalidates DEV_BSIZE'd chunks within a page. Both the
1559 * valid and dirty bits for the effected areas are cleared.
1564 vm_page_set_invalid(vm_page_t m, int base, int size)
1568 VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
1569 bits = vm_page_bits(base, size);
1570 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
1573 m->object->generation++;
1577 * vm_page_zero_invalid()
1579 * The kernel assumes that the invalid portions of a page contain
1580 * garbage, but such pages can be mapped into memory by user code.
1581 * When this occurs, we must zero out the non-valid portions of the
1582 * page so user code sees what it expects.
1584 * Pages are most often semi-valid when the end of a file is mapped
1585 * into memory and the file's size is not page aligned.
1588 vm_page_zero_invalid(vm_page_t m, boolean_t setvalid)
1593 VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
1595 * Scan the valid bits looking for invalid sections that
1596 * must be zerod. Invalid sub-DEV_BSIZE'd areas ( where the
1597 * valid bit may be set ) have already been zerod by
1598 * vm_page_set_validclean().
1600 for (b = i = 0; i <= PAGE_SIZE / DEV_BSIZE; ++i) {
1601 if (i == (PAGE_SIZE / DEV_BSIZE) ||
1602 (m->valid & (1 << i))
1605 pmap_zero_page_area(m,
1606 b << DEV_BSHIFT, (i - b) << DEV_BSHIFT);
1613 * setvalid is TRUE when we can safely set the zero'd areas
1614 * as being valid. We can do this if there are no cache consistancy
1615 * issues. e.g. it is ok to do with UFS, but not ok to do with NFS.
1618 m->valid = VM_PAGE_BITS_ALL;
1624 * Is (partial) page valid? Note that the case where size == 0
1625 * will return FALSE in the degenerate case where the page is
1626 * entirely invalid, and TRUE otherwise.
1631 vm_page_is_valid(vm_page_t m, int base, int size)
1633 int bits = vm_page_bits(base, size);
1635 VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
1636 if (m->valid && ((m->valid & bits) == bits))
1643 * update dirty bits from pmap/mmu. May not block.
1646 vm_page_test_dirty(vm_page_t m)
1648 if ((m->dirty != VM_PAGE_BITS_ALL) && pmap_is_modified(m)) {
1653 int so_zerocp_fullpage = 0;
1656 vm_page_cowfault(vm_page_t m)
1668 mnew = vm_page_alloc(object, pindex, VM_ALLOC_NORMAL);
1670 vm_page_insert(m, object, pindex);
1671 vm_page_unlock_queues();
1672 VM_OBJECT_UNLOCK(object);
1674 VM_OBJECT_LOCK(object);
1675 vm_page_lock_queues();
1681 * check to see if we raced with an xmit complete when
1682 * waiting to allocate a page. If so, put things back
1686 vm_page_insert(m, object, pindex);
1687 } else { /* clear COW & copy page */
1688 if (!so_zerocp_fullpage)
1689 pmap_copy_page(m, mnew);
1690 mnew->valid = VM_PAGE_BITS_ALL;
1691 vm_page_dirty(mnew);
1692 vm_page_flag_clear(mnew, PG_BUSY);
1697 vm_page_cowclear(vm_page_t m)
1700 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
1704 * let vm_fault add back write permission lazily
1708 * sf_buf_free() will free the page, so we needn't do it here
1713 vm_page_cowsetup(vm_page_t m)
1716 mtx_assert(&vm_page_queue_mtx, MA_OWNED);
1718 pmap_page_protect(m, VM_PROT_READ);
1721 #include "opt_ddb.h"
1723 #include <sys/kernel.h>
1725 #include <ddb/ddb.h>
1727 DB_SHOW_COMMAND(page, vm_page_print_page_info)
1729 db_printf("cnt.v_free_count: %d\n", cnt.v_free_count);
1730 db_printf("cnt.v_cache_count: %d\n", cnt.v_cache_count);
1731 db_printf("cnt.v_inactive_count: %d\n", cnt.v_inactive_count);
1732 db_printf("cnt.v_active_count: %d\n", cnt.v_active_count);
1733 db_printf("cnt.v_wire_count: %d\n", cnt.v_wire_count);
1734 db_printf("cnt.v_free_reserved: %d\n", cnt.v_free_reserved);
1735 db_printf("cnt.v_free_min: %d\n", cnt.v_free_min);
1736 db_printf("cnt.v_free_target: %d\n", cnt.v_free_target);
1737 db_printf("cnt.v_cache_min: %d\n", cnt.v_cache_min);
1738 db_printf("cnt.v_inactive_target: %d\n", cnt.v_inactive_target);
1741 DB_SHOW_COMMAND(pageq, vm_page_print_pageq_info)
1744 db_printf("PQ_FREE:");
1745 for (i = 0; i < PQ_L2_SIZE; i++) {
1746 db_printf(" %d", vm_page_queues[PQ_FREE + i].lcnt);
1750 db_printf("PQ_CACHE:");
1751 for (i = 0; i < PQ_L2_SIZE; i++) {
1752 db_printf(" %d", vm_page_queues[PQ_CACHE + i].lcnt);
1756 db_printf("PQ_ACTIVE: %d, PQ_INACTIVE: %d\n",
1757 vm_page_queues[PQ_ACTIVE].lcnt,
1758 vm_page_queues[PQ_INACTIVE].lcnt);