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 * 3. All advertising materials mentioning features or use of this software
17 * must display the following acknowledgement:
18 * This product includes software developed by the University of
19 * California, Berkeley and its contributors.
20 * 4. Neither the name of the University nor the names of its contributors
21 * may be used to endorse or promote products derived from this software
22 * without specific prior written permission.
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * from: @(#)vm_page.c 7.4 (Berkeley) 5/7/91
37 * $FreeBSD: src/sys/vm/vm_page.c,v 1.147.2.18 2002/03/10 05:03:19 alc Exp $
38 * $DragonFly: src/sys/vm/vm_page.c,v 1.40 2008/08/25 17:01:42 dillon Exp $
42 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
43 * All rights reserved.
45 * Authors: Avadis Tevanian, Jr., Michael Wayne Young
47 * Permission to use, copy, modify and distribute this software and
48 * its documentation is hereby granted, provided that both the copyright
49 * notice and this permission notice appear in all copies of the
50 * software, derivative works or modified versions, and any portions
51 * thereof, and that both notices appear in supporting documentation.
53 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
54 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
55 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
57 * Carnegie Mellon requests users of this software to return to
59 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
60 * School of Computer Science
61 * Carnegie Mellon University
62 * Pittsburgh PA 15213-3890
64 * any improvements or extensions that they make and grant Carnegie the
65 * rights to redistribute these changes.
68 * Resident memory management module. The module manipulates 'VM pages'.
69 * A VM page is the core building block for memory management.
72 #include <sys/param.h>
73 #include <sys/systm.h>
74 #include <sys/malloc.h>
76 #include <sys/vmmeter.h>
77 #include <sys/vnode.h>
80 #include <vm/vm_param.h>
82 #include <vm/vm_kern.h>
84 #include <vm/vm_map.h>
85 #include <vm/vm_object.h>
86 #include <vm/vm_page.h>
87 #include <vm/vm_pageout.h>
88 #include <vm/vm_pager.h>
89 #include <vm/vm_extern.h>
90 #include <vm/vm_page2.h>
92 static void vm_page_queue_init(void);
93 static void vm_page_free_wakeup(void);
94 static vm_page_t vm_page_select_cache(vm_object_t, vm_pindex_t);
95 static vm_page_t _vm_page_list_find2(int basequeue, int index);
97 struct vpgqueues vm_page_queues[PQ_COUNT]; /* Array of tailq lists */
99 #define ASSERT_IN_CRIT_SECTION() KKASSERT(crit_test(curthread));
101 RB_GENERATE2(vm_page_rb_tree, vm_page, rb_entry, rb_vm_page_compare,
102 vm_pindex_t, pindex);
105 vm_page_queue_init(void)
109 for (i = 0; i < PQ_L2_SIZE; i++)
110 vm_page_queues[PQ_FREE+i].cnt = &vmstats.v_free_count;
111 for (i = 0; i < PQ_L2_SIZE; i++)
112 vm_page_queues[PQ_CACHE+i].cnt = &vmstats.v_cache_count;
114 vm_page_queues[PQ_INACTIVE].cnt = &vmstats.v_inactive_count;
115 vm_page_queues[PQ_ACTIVE].cnt = &vmstats.v_active_count;
116 vm_page_queues[PQ_HOLD].cnt = &vmstats.v_active_count;
117 /* PQ_NONE has no queue */
119 for (i = 0; i < PQ_COUNT; i++)
120 TAILQ_INIT(&vm_page_queues[i].pl);
124 * note: place in initialized data section? Is this necessary?
127 int vm_page_array_size = 0;
128 int vm_page_zero_count = 0;
129 vm_page_t vm_page_array = 0;
134 * Sets the page size, perhaps based upon the memory size.
135 * Must be called before any use of page-size dependent functions.
138 vm_set_page_size(void)
140 if (vmstats.v_page_size == 0)
141 vmstats.v_page_size = PAGE_SIZE;
142 if (((vmstats.v_page_size - 1) & vmstats.v_page_size) != 0)
143 panic("vm_set_page_size: page size not a power of two");
149 * Add a new page to the freelist for use by the system. New pages
150 * are added to both the head and tail of the associated free page
151 * queue in a bottom-up fashion, so both zero'd and non-zero'd page
152 * requests pull 'recent' adds (higher physical addresses) first.
154 * Must be called in a critical section.
157 vm_add_new_page(vm_paddr_t pa)
159 struct vpgqueues *vpq;
162 ++vmstats.v_page_count;
163 ++vmstats.v_free_count;
164 m = PHYS_TO_VM_PAGE(pa);
167 m->pc = (pa >> PAGE_SHIFT) & PQ_L2_MASK;
168 m->queue = m->pc + PQ_FREE;
169 KKASSERT(m->dirty == 0);
171 vpq = &vm_page_queues[m->queue];
173 TAILQ_INSERT_TAIL(&vpq->pl, m, pageq);
175 TAILQ_INSERT_HEAD(&vpq->pl, m, pageq);
176 vpq->flipflop = 1 - vpq->flipflop;
178 vm_page_queues[m->queue].lcnt++;
185 * Initializes the resident memory module.
187 * Allocates memory for the page cells, and for the object/offset-to-page
188 * hash table headers. Each page cell is initialized and placed on the
191 * starta/enda represents the range of physical memory addresses available
192 * for use (skipping memory already used by the kernel), subject to
193 * phys_avail[]. Note that phys_avail[] has already mapped out memory
194 * already in use by the kernel.
197 vm_page_startup(vm_offset_t vaddr)
201 vm_paddr_t page_range;
208 vm_paddr_t biggestone, biggestsize;
215 vaddr = round_page(vaddr);
217 for (i = 0; phys_avail[i + 1]; i += 2) {
218 phys_avail[i] = round_page(phys_avail[i]);
219 phys_avail[i + 1] = trunc_page(phys_avail[i + 1]);
222 for (i = 0; phys_avail[i + 1]; i += 2) {
223 vm_paddr_t size = phys_avail[i + 1] - phys_avail[i];
225 if (size > biggestsize) {
233 end = phys_avail[biggestone+1];
234 end = trunc_page(end);
237 * Initialize the queue headers for the free queue, the active queue
238 * and the inactive queue.
241 vm_page_queue_init();
244 * Compute the number of pages of memory that will be available for
245 * use (taking into account the overhead of a page structure per
248 first_page = phys_avail[0] / PAGE_SIZE;
249 page_range = phys_avail[(nblocks - 1) * 2 + 1] / PAGE_SIZE - first_page;
250 npages = (total - (page_range * sizeof(struct vm_page))) / PAGE_SIZE;
253 * Initialize the mem entry structures now, and put them in the free
256 vm_page_array = (vm_page_t) vaddr;
260 * Validate these addresses.
262 new_end = trunc_page(end - page_range * sizeof(struct vm_page));
263 mapped = pmap_map(mapped, new_end, end,
264 VM_PROT_READ | VM_PROT_WRITE);
267 * Clear all of the page structures
269 bzero((caddr_t) vm_page_array, page_range * sizeof(struct vm_page));
270 vm_page_array_size = page_range;
273 * Construct the free queue(s) in ascending order (by physical
274 * address) so that the first 16MB of physical memory is allocated
275 * last rather than first. On large-memory machines, this avoids
276 * the exhaustion of low physical memory before isa_dmainit has run.
278 vmstats.v_page_count = 0;
279 vmstats.v_free_count = 0;
280 for (i = 0; phys_avail[i + 1] && npages > 0; i += 2) {
285 last_pa = phys_avail[i + 1];
286 while (pa < last_pa && npages-- > 0) {
295 * Scan comparison function for Red-Black tree scans. An inclusive
296 * (start,end) is expected. Other fields are not used.
299 rb_vm_page_scancmp(struct vm_page *p, void *data)
301 struct rb_vm_page_scan_info *info = data;
303 if (p->pindex < info->start_pindex)
305 if (p->pindex > info->end_pindex)
311 rb_vm_page_compare(struct vm_page *p1, struct vm_page *p2)
313 if (p1->pindex < p2->pindex)
315 if (p1->pindex > p2->pindex)
321 * The opposite of vm_page_hold(). A page can be freed while being held,
322 * which places it on the PQ_HOLD queue. We must call vm_page_free_toq()
323 * in this case to actually free it once the hold count drops to 0.
325 * This routine must be called at splvm().
328 vm_page_unhold(vm_page_t mem)
331 KASSERT(mem->hold_count >= 0, ("vm_page_unhold: hold count < 0!!!"));
332 if (mem->hold_count == 0 && mem->queue == PQ_HOLD) {
334 vm_page_free_toq(mem);
339 * Inserts the given mem entry into the object and object list.
341 * The pagetables are not updated but will presumably fault the page
342 * in if necessary, or if a kernel page the caller will at some point
343 * enter the page into the kernel's pmap. We are not allowed to block
344 * here so we *can't* do this anyway.
346 * This routine may not block.
347 * This routine must be called with a critical section held.
350 vm_page_insert(vm_page_t m, vm_object_t object, vm_pindex_t pindex)
352 ASSERT_IN_CRIT_SECTION();
353 if (m->object != NULL)
354 panic("vm_page_insert: already inserted");
357 * Record the object/offset pair in this page
363 * Insert it into the object.
365 vm_page_rb_tree_RB_INSERT(&object->rb_memq, m);
366 object->generation++;
369 * show that the object has one more resident page.
371 object->resident_page_count++;
374 * Since we are inserting a new and possibly dirty page,
375 * update the object's OBJ_WRITEABLE and OBJ_MIGHTBEDIRTY flags.
377 if ((m->valid & m->dirty) || (m->flags & PG_WRITEABLE))
378 vm_object_set_writeable_dirty(object);
382 * Removes the given vm_page_t from the global (object,index) hash table
383 * and from the object's memq.
385 * The underlying pmap entry (if any) is NOT removed here.
386 * This routine may not block.
388 * The page must be BUSY and will remain BUSY on return. No spl needs to be
389 * held on call to this routine.
391 * note: FreeBSD side effect was to unbusy the page on return. We leave
395 vm_page_remove(vm_page_t m)
400 if (m->object == NULL) {
405 if ((m->flags & PG_BUSY) == 0)
406 panic("vm_page_remove: page not busy");
411 * Remove the page from the object and update the object.
413 vm_page_rb_tree_RB_REMOVE(&object->rb_memq, m);
414 object->resident_page_count--;
415 object->generation++;
422 * Locate and return the page at (object, pindex), or NULL if the
423 * page could not be found.
425 * This routine will operate properly without spl protection, but
426 * the returned page could be in flux if it is busy. Because an
427 * interrupt can race a caller's busy check (unbusying and freeing the
428 * page we return before the caller is able to check the busy bit),
429 * the caller should generally call this routine with a critical
432 * Callers may call this routine without spl protection if they know
433 * 'for sure' that the page will not be ripped out from under them
437 vm_page_lookup(vm_object_t object, vm_pindex_t pindex)
442 * Search the hash table for this object/offset pair
445 m = vm_page_rb_tree_RB_LOOKUP(&object->rb_memq, pindex);
447 KKASSERT(m == NULL || (m->object == object && m->pindex == pindex));
454 * Move the given memory entry from its current object to the specified
455 * target object/offset.
457 * The object must be locked.
458 * This routine may not block.
460 * Note: This routine will raise itself to splvm(), the caller need not.
462 * Note: Swap associated with the page must be invalidated by the move. We
463 * have to do this for several reasons: (1) we aren't freeing the
464 * page, (2) we are dirtying the page, (3) the VM system is probably
465 * moving the page from object A to B, and will then later move
466 * the backing store from A to B and we can't have a conflict.
468 * Note: We *always* dirty the page. It is necessary both for the
469 * fact that we moved it, and because we may be invalidating
470 * swap. If the page is on the cache, we have to deactivate it
471 * or vm_page_dirty() will panic. Dirty pages are not allowed
475 vm_page_rename(vm_page_t m, vm_object_t new_object, vm_pindex_t new_pindex)
479 vm_page_insert(m, new_object, new_pindex);
480 if (m->queue - m->pc == PQ_CACHE)
481 vm_page_deactivate(m);
488 * vm_page_unqueue() without any wakeup. This routine is used when a page
489 * is being moved between queues or otherwise is to remain BUSYied by the
492 * This routine must be called at splhigh().
493 * This routine may not block.
496 vm_page_unqueue_nowakeup(vm_page_t m)
498 int queue = m->queue;
499 struct vpgqueues *pq;
501 if (queue != PQ_NONE) {
502 pq = &vm_page_queues[queue];
504 TAILQ_REMOVE(&pq->pl, m, pageq);
511 * vm_page_unqueue() - Remove a page from its queue, wakeup the pagedemon
514 * This routine must be called at splhigh().
515 * This routine may not block.
518 vm_page_unqueue(vm_page_t m)
520 int queue = m->queue;
521 struct vpgqueues *pq;
523 if (queue != PQ_NONE) {
525 pq = &vm_page_queues[queue];
526 TAILQ_REMOVE(&pq->pl, m, pageq);
529 if ((queue - m->pc) == PQ_CACHE || (queue - m->pc) == PQ_FREE)
535 * vm_page_list_find()
537 * Find a page on the specified queue with color optimization.
539 * The page coloring optimization attempts to locate a page that does
540 * not overload other nearby pages in the object in the cpu's L1 or L2
541 * caches. We need this optimization because cpu caches tend to be
542 * physical caches, while object spaces tend to be virtual.
544 * This routine must be called at splvm().
545 * This routine may not block.
547 * Note that this routine is carefully inlined. A non-inlined version
548 * is available for outside callers but the only critical path is
549 * from within this source file.
553 _vm_page_list_find(int basequeue, int index, boolean_t prefer_zero)
558 m = TAILQ_LAST(&vm_page_queues[basequeue+index].pl, pglist);
560 m = TAILQ_FIRST(&vm_page_queues[basequeue+index].pl);
562 m = _vm_page_list_find2(basequeue, index);
567 _vm_page_list_find2(int basequeue, int index)
571 struct vpgqueues *pq;
573 pq = &vm_page_queues[basequeue];
576 * Note that for the first loop, index+i and index-i wind up at the
577 * same place. Even though this is not totally optimal, we've already
578 * blown it by missing the cache case so we do not care.
581 for(i = PQ_L2_SIZE / 2; i > 0; --i) {
582 if ((m = TAILQ_FIRST(&pq[(index + i) & PQ_L2_MASK].pl)) != NULL)
585 if ((m = TAILQ_FIRST(&pq[(index - i) & PQ_L2_MASK].pl)) != NULL)
592 vm_page_list_find(int basequeue, int index, boolean_t prefer_zero)
594 return(_vm_page_list_find(basequeue, index, prefer_zero));
598 * Find a page on the cache queue with color optimization. As pages
599 * might be found, but not applicable, they are deactivated. This
600 * keeps us from using potentially busy cached pages.
602 * This routine must be called with a critical section held.
603 * This routine may not block.
606 vm_page_select_cache(vm_object_t object, vm_pindex_t pindex)
611 m = _vm_page_list_find(
613 (pindex + object->pg_color) & PQ_L2_MASK,
616 if (m && ((m->flags & (PG_BUSY|PG_UNMANAGED)) || m->busy ||
617 m->hold_count || m->wire_count)) {
618 vm_page_deactivate(m);
627 * Find a free or zero page, with specified preference. We attempt to
628 * inline the nominal case and fall back to _vm_page_select_free()
631 * This routine must be called with a critical section held.
632 * This routine may not block.
634 static __inline vm_page_t
635 vm_page_select_free(vm_object_t object, vm_pindex_t pindex, boolean_t prefer_zero)
639 m = _vm_page_list_find(
641 (pindex + object->pg_color) & PQ_L2_MASK,
650 * Allocate and return a memory cell associated with this VM object/offset
655 * VM_ALLOC_NORMAL allow use of cache pages, nominal free drain
656 * VM_ALLOC_SYSTEM greater free drain
657 * VM_ALLOC_INTERRUPT allow free list to be completely drained
658 * VM_ALLOC_ZERO advisory request for pre-zero'd page
660 * The object must be locked.
661 * This routine may not block.
662 * The returned page will be marked PG_BUSY
664 * Additional special handling is required when called from an interrupt
665 * (VM_ALLOC_INTERRUPT). We are not allowed to mess with the page cache
669 vm_page_alloc(vm_object_t object, vm_pindex_t pindex, int page_req)
673 KKASSERT(object != NULL);
674 KASSERT(!vm_page_lookup(object, pindex),
675 ("vm_page_alloc: page already allocated"));
677 (VM_ALLOC_NORMAL|VM_ALLOC_INTERRUPT|VM_ALLOC_SYSTEM));
680 * Certain system threads (pageout daemon, buf_daemon's) are
681 * allowed to eat deeper into the free page list.
683 if (curthread->td_flags & TDF_SYSTHREAD)
684 page_req |= VM_ALLOC_SYSTEM;
688 if (vmstats.v_free_count > vmstats.v_free_reserved ||
689 ((page_req & VM_ALLOC_INTERRUPT) && vmstats.v_free_count > 0) ||
690 ((page_req & VM_ALLOC_SYSTEM) && vmstats.v_cache_count == 0 &&
691 vmstats.v_free_count > vmstats.v_interrupt_free_min)
694 * The free queue has sufficient free pages to take one out.
696 if (page_req & VM_ALLOC_ZERO)
697 m = vm_page_select_free(object, pindex, TRUE);
699 m = vm_page_select_free(object, pindex, FALSE);
700 } else if (page_req & VM_ALLOC_NORMAL) {
702 * Allocatable from the cache (non-interrupt only). On
703 * success, we must free the page and try again, thus
704 * ensuring that vmstats.v_*_free_min counters are replenished.
707 if (curthread->td_preempted) {
708 kprintf("vm_page_alloc(): warning, attempt to allocate"
709 " cache page from preempting interrupt\n");
712 m = vm_page_select_cache(object, pindex);
715 m = vm_page_select_cache(object, pindex);
718 * On success move the page into the free queue and loop.
721 KASSERT(m->dirty == 0,
722 ("Found dirty cache page %p", m));
724 vm_page_protect(m, VM_PROT_NONE);
730 * On failure return NULL
733 #if defined(DIAGNOSTIC)
734 if (vmstats.v_cache_count > 0)
735 kprintf("vm_page_alloc(NORMAL): missing pages on cache queue: %d\n", vmstats.v_cache_count);
737 vm_pageout_deficit++;
742 * No pages available, wakeup the pageout daemon and give up.
745 vm_pageout_deficit++;
751 * Good page found. The page has not yet been busied. We are in
752 * a critical section.
754 KASSERT(m != NULL, ("vm_page_alloc(): missing page on free queue\n"));
755 KASSERT(m->dirty == 0,
756 ("vm_page_alloc: free/cache page %p was dirty", m));
759 * Remove from free queue
761 vm_page_unqueue_nowakeup(m);
764 * Initialize structure. Only the PG_ZERO flag is inherited. Set
767 if (m->flags & PG_ZERO) {
768 vm_page_zero_count--;
769 m->flags = PG_ZERO | PG_BUSY;
780 * vm_page_insert() is safe prior to the crit_exit(). Note also that
781 * inserting a page here does not insert it into the pmap (which
782 * could cause us to block allocating memory). We cannot block
785 vm_page_insert(m, object, pindex);
788 * Don't wakeup too often - wakeup the pageout daemon when
789 * we would be nearly out of memory.
796 * A PG_BUSY page is returned.
802 * Block until free pages are available for allocation, called in various
803 * places before memory allocations.
809 if (curthread == pagethread) {
810 vm_pageout_pages_needed = 1;
811 tsleep(&vm_pageout_pages_needed, 0, "VMWait", timo);
813 if (vm_pages_needed == 0) {
815 wakeup(&vm_pages_needed);
817 tsleep(&vmstats.v_free_count, 0, "vmwait", timo);
823 * Block until free pages are available for allocation
825 * Called only in vm_fault so that processes page faulting can be
832 if (vm_pages_needed == 0) {
834 wakeup(&vm_pages_needed);
836 tsleep(&vmstats.v_free_count, 0, "pfault", 0);
841 * Put the specified page on the active list (if appropriate). Ensure
842 * that act_count is at least ACT_INIT but do not otherwise mess with it.
844 * The page queues must be locked.
845 * This routine may not block.
848 vm_page_activate(vm_page_t m)
851 if (m->queue != PQ_ACTIVE) {
852 if ((m->queue - m->pc) == PQ_CACHE)
853 mycpu->gd_cnt.v_reactivated++;
857 if (m->wire_count == 0 && (m->flags & PG_UNMANAGED) == 0) {
858 m->queue = PQ_ACTIVE;
859 vm_page_queues[PQ_ACTIVE].lcnt++;
860 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl,
862 if (m->act_count < ACT_INIT)
863 m->act_count = ACT_INIT;
864 vmstats.v_active_count++;
867 if (m->act_count < ACT_INIT)
868 m->act_count = ACT_INIT;
874 * Helper routine for vm_page_free_toq() and vm_page_cache(). This
875 * routine is called when a page has been added to the cache or free
878 * This routine may not block.
879 * This routine must be called at splvm()
882 vm_page_free_wakeup(void)
885 * if pageout daemon needs pages, then tell it that there are
888 if (vm_pageout_pages_needed &&
889 vmstats.v_cache_count + vmstats.v_free_count >=
890 vmstats.v_pageout_free_min
892 wakeup(&vm_pageout_pages_needed);
893 vm_pageout_pages_needed = 0;
897 * wakeup processes that are waiting on memory if we hit a
898 * high water mark. And wakeup scheduler process if we have
899 * lots of memory. this process will swapin processes.
901 if (vm_pages_needed && !vm_page_count_min(0)) {
903 wakeup(&vmstats.v_free_count);
910 * Returns the given page to the PQ_FREE list, disassociating it with
913 * The vm_page must be PG_BUSY on entry. PG_BUSY will be released on
914 * return (the page will have been freed). No particular spl is required
917 * This routine may not block.
920 vm_page_free_toq(vm_page_t m)
922 struct vpgqueues *pq;
925 mycpu->gd_cnt.v_tfree++;
927 KKASSERT((m->flags & PG_MAPPED) == 0);
929 if (m->busy || ((m->queue - m->pc) == PQ_FREE)) {
931 "vm_page_free: pindex(%lu), busy(%d), PG_BUSY(%d), hold(%d)\n",
932 (u_long)m->pindex, m->busy, (m->flags & PG_BUSY) ? 1 : 0,
934 if ((m->queue - m->pc) == PQ_FREE)
935 panic("vm_page_free: freeing free page");
937 panic("vm_page_free: freeing busy page");
941 * unqueue, then remove page. Note that we cannot destroy
942 * the page here because we do not want to call the pager's
943 * callback routine until after we've put the page on the
944 * appropriate free queue.
946 vm_page_unqueue_nowakeup(m);
950 * No further management of fictitious pages occurs beyond object
953 if ((m->flags & PG_FICTITIOUS) != 0) {
962 if (m->wire_count != 0) {
963 if (m->wire_count > 1) {
965 "vm_page_free: invalid wire count (%d), pindex: 0x%lx",
966 m->wire_count, (long)m->pindex);
968 panic("vm_page_free: freeing wired page");
972 * Clear the UNMANAGED flag when freeing an unmanaged page.
974 if (m->flags & PG_UNMANAGED) {
975 m->flags &= ~PG_UNMANAGED;
978 if (m->hold_count != 0) {
979 m->flags &= ~PG_ZERO;
982 m->queue = PQ_FREE + m->pc;
984 pq = &vm_page_queues[m->queue];
989 * Put zero'd pages on the end ( where we look for zero'd pages
990 * first ) and non-zerod pages at the head.
992 if (m->flags & PG_ZERO) {
993 TAILQ_INSERT_TAIL(&pq->pl, m, pageq);
994 ++vm_page_zero_count;
996 TAILQ_INSERT_HEAD(&pq->pl, m, pageq);
999 vm_page_free_wakeup();
1004 * vm_page_unmanage()
1006 * Prevent PV management from being done on the page. The page is
1007 * removed from the paging queues as if it were wired, and as a
1008 * consequence of no longer being managed the pageout daemon will not
1009 * touch it (since there is no way to locate the pte mappings for the
1010 * page). madvise() calls that mess with the pmap will also no longer
1011 * operate on the page.
1013 * Beyond that the page is still reasonably 'normal'. Freeing the page
1014 * will clear the flag.
1016 * This routine is used by OBJT_PHYS objects - objects using unswappable
1017 * physical memory as backing store rather then swap-backed memory and
1018 * will eventually be extended to support 4MB unmanaged physical
1021 * Must be called with a critical section held.
1024 vm_page_unmanage(vm_page_t m)
1026 ASSERT_IN_CRIT_SECTION();
1027 if ((m->flags & PG_UNMANAGED) == 0) {
1028 if (m->wire_count == 0)
1031 vm_page_flag_set(m, PG_UNMANAGED);
1035 * Mark this page as wired down by yet another map, removing it from
1036 * paging queues as necessary.
1038 * The page queues must be locked.
1039 * This routine may not block.
1042 vm_page_wire(vm_page_t m)
1045 * Only bump the wire statistics if the page is not already wired,
1046 * and only unqueue the page if it is on some queue (if it is unmanaged
1047 * it is already off the queues). Don't do anything with fictitious
1048 * pages because they are always wired.
1051 if ((m->flags & PG_FICTITIOUS) == 0) {
1052 if (m->wire_count == 0) {
1053 if ((m->flags & PG_UNMANAGED) == 0)
1055 vmstats.v_wire_count++;
1058 KASSERT(m->wire_count != 0,
1059 ("vm_page_wire: wire_count overflow m=%p", m));
1065 * Release one wiring of this page, potentially enabling it to be paged again.
1067 * Many pages placed on the inactive queue should actually go
1068 * into the cache, but it is difficult to figure out which. What
1069 * we do instead, if the inactive target is well met, is to put
1070 * clean pages at the head of the inactive queue instead of the tail.
1071 * This will cause them to be moved to the cache more quickly and
1072 * if not actively re-referenced, freed more quickly. If we just
1073 * stick these pages at the end of the inactive queue, heavy filesystem
1074 * meta-data accesses can cause an unnecessary paging load on memory bound
1075 * processes. This optimization causes one-time-use metadata to be
1076 * reused more quickly.
1078 * BUT, if we are in a low-memory situation we have no choice but to
1079 * put clean pages on the cache queue.
1081 * A number of routines use vm_page_unwire() to guarantee that the page
1082 * will go into either the inactive or active queues, and will NEVER
1083 * be placed in the cache - for example, just after dirtying a page.
1084 * dirty pages in the cache are not allowed.
1086 * The page queues must be locked.
1087 * This routine may not block.
1090 vm_page_unwire(vm_page_t m, int activate)
1093 if (m->flags & PG_FICTITIOUS) {
1095 } else if (m->wire_count <= 0) {
1096 panic("vm_page_unwire: invalid wire count: %d", m->wire_count);
1098 if (--m->wire_count == 0) {
1099 --vmstats.v_wire_count;
1100 if (m->flags & PG_UNMANAGED) {
1102 } else if (activate) {
1104 &vm_page_queues[PQ_ACTIVE].pl, m, pageq);
1105 m->queue = PQ_ACTIVE;
1106 vm_page_queues[PQ_ACTIVE].lcnt++;
1107 vmstats.v_active_count++;
1109 vm_page_flag_clear(m, PG_WINATCFLS);
1111 &vm_page_queues[PQ_INACTIVE].pl, m, pageq);
1112 m->queue = PQ_INACTIVE;
1113 vm_page_queues[PQ_INACTIVE].lcnt++;
1114 vmstats.v_inactive_count++;
1123 * Move the specified page to the inactive queue. If the page has
1124 * any associated swap, the swap is deallocated.
1126 * Normally athead is 0 resulting in LRU operation. athead is set
1127 * to 1 if we want this page to be 'as if it were placed in the cache',
1128 * except without unmapping it from the process address space.
1130 * This routine may not block.
1132 static __inline void
1133 _vm_page_deactivate(vm_page_t m, int athead)
1136 * Ignore if already inactive.
1138 if (m->queue == PQ_INACTIVE)
1141 if (m->wire_count == 0 && (m->flags & PG_UNMANAGED) == 0) {
1142 if ((m->queue - m->pc) == PQ_CACHE)
1143 mycpu->gd_cnt.v_reactivated++;
1144 vm_page_flag_clear(m, PG_WINATCFLS);
1147 TAILQ_INSERT_HEAD(&vm_page_queues[PQ_INACTIVE].pl, m, pageq);
1149 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_INACTIVE].pl, m, pageq);
1150 m->queue = PQ_INACTIVE;
1151 vm_page_queues[PQ_INACTIVE].lcnt++;
1152 vmstats.v_inactive_count++;
1157 vm_page_deactivate(vm_page_t m)
1160 _vm_page_deactivate(m, 0);
1165 * vm_page_try_to_cache:
1167 * Returns 0 on failure, 1 on success
1170 vm_page_try_to_cache(vm_page_t m)
1173 if (m->dirty || m->hold_count || m->busy || m->wire_count ||
1174 (m->flags & (PG_BUSY|PG_UNMANAGED))) {
1178 vm_page_test_dirty(m);
1189 * Attempt to free the page. If we cannot free it, we do nothing.
1190 * 1 is returned on success, 0 on failure.
1193 vm_page_try_to_free(vm_page_t m)
1196 if (m->dirty || m->hold_count || m->busy || m->wire_count ||
1197 (m->flags & (PG_BUSY|PG_UNMANAGED))) {
1201 vm_page_test_dirty(m);
1207 vm_page_protect(m, VM_PROT_NONE);
1216 * Put the specified page onto the page cache queue (if appropriate).
1218 * This routine may not block.
1221 vm_page_cache(vm_page_t m)
1223 ASSERT_IN_CRIT_SECTION();
1225 if ((m->flags & (PG_BUSY|PG_UNMANAGED)) || m->busy ||
1226 m->wire_count || m->hold_count) {
1227 kprintf("vm_page_cache: attempting to cache busy/held page\n");
1232 * Already in the cache (and thus not mapped)
1234 if ((m->queue - m->pc) == PQ_CACHE) {
1235 KKASSERT((m->flags & PG_MAPPED) == 0);
1240 * Caller is required to test m->dirty, but note that the act of
1241 * removing the page from its maps can cause it to become dirty
1242 * on an SMP system due to another cpu running in usermode.
1245 panic("vm_page_cache: caching a dirty page, pindex: %ld",
1250 * Remove all pmaps and indicate that the page is not
1251 * writeable or mapped. Our vm_page_protect() call may
1252 * have blocked (especially w/ VM_PROT_NONE), so recheck
1256 vm_page_protect(m, VM_PROT_NONE);
1258 if ((m->flags & (PG_BUSY|PG_UNMANAGED|PG_MAPPED)) || m->busy ||
1259 m->wire_count || m->hold_count) {
1261 } else if (m->dirty) {
1262 vm_page_deactivate(m);
1264 vm_page_unqueue_nowakeup(m);
1265 m->queue = PQ_CACHE + m->pc;
1266 vm_page_queues[m->queue].lcnt++;
1267 TAILQ_INSERT_TAIL(&vm_page_queues[m->queue].pl, m, pageq);
1268 vmstats.v_cache_count++;
1269 vm_page_free_wakeup();
1274 * vm_page_dontneed()
1276 * Cache, deactivate, or do nothing as appropriate. This routine
1277 * is typically used by madvise() MADV_DONTNEED.
1279 * Generally speaking we want to move the page into the cache so
1280 * it gets reused quickly. However, this can result in a silly syndrome
1281 * due to the page recycling too quickly. Small objects will not be
1282 * fully cached. On the otherhand, if we move the page to the inactive
1283 * queue we wind up with a problem whereby very large objects
1284 * unnecessarily blow away our inactive and cache queues.
1286 * The solution is to move the pages based on a fixed weighting. We
1287 * either leave them alone, deactivate them, or move them to the cache,
1288 * where moving them to the cache has the highest weighting.
1289 * By forcing some pages into other queues we eventually force the
1290 * system to balance the queues, potentially recovering other unrelated
1291 * space from active. The idea is to not force this to happen too
1295 vm_page_dontneed(vm_page_t m)
1297 static int dnweight;
1304 * occassionally leave the page alone
1307 if ((dnw & 0x01F0) == 0 ||
1308 m->queue == PQ_INACTIVE ||
1309 m->queue - m->pc == PQ_CACHE
1311 if (m->act_count >= ACT_INIT)
1318 vm_page_test_dirty(m);
1320 if (m->dirty || (dnw & 0x0070) == 0) {
1322 * Deactivate the page 3 times out of 32.
1327 * Cache the page 28 times out of every 32. Note that
1328 * the page is deactivated instead of cached, but placed
1329 * at the head of the queue instead of the tail.
1333 _vm_page_deactivate(m, head);
1338 * Grab a page, blocking if it is busy and allocating a page if necessary.
1339 * A busy page is returned or NULL.
1341 * If VM_ALLOC_RETRY is specified VM_ALLOC_NORMAL must also be specified.
1342 * If VM_ALLOC_RETRY is not specified
1344 * This routine may block, but if VM_ALLOC_RETRY is not set then NULL is
1345 * always returned if we had blocked.
1346 * This routine will never return NULL if VM_ALLOC_RETRY is set.
1347 * This routine may not be called from an interrupt.
1348 * The returned page may not be entirely valid.
1350 * This routine may be called from mainline code without spl protection and
1351 * be guarenteed a busied page associated with the object at the specified
1355 vm_page_grab(vm_object_t object, vm_pindex_t pindex, int allocflags)
1360 KKASSERT(allocflags &
1361 (VM_ALLOC_NORMAL|VM_ALLOC_INTERRUPT|VM_ALLOC_SYSTEM));
1364 if ((m = vm_page_lookup(object, pindex)) != NULL) {
1365 if (m->busy || (m->flags & PG_BUSY)) {
1366 generation = object->generation;
1368 while ((object->generation == generation) &&
1369 (m->busy || (m->flags & PG_BUSY))) {
1370 vm_page_flag_set(m, PG_WANTED | PG_REFERENCED);
1371 tsleep(m, 0, "pgrbwt", 0);
1372 if ((allocflags & VM_ALLOC_RETRY) == 0) {
1383 m = vm_page_alloc(object, pindex, allocflags & ~VM_ALLOC_RETRY);
1386 if ((allocflags & VM_ALLOC_RETRY) == 0)
1396 * Mapping function for valid bits or for dirty bits in
1397 * a page. May not block.
1399 * Inputs are required to range within a page.
1402 vm_page_bits(int base, int size)
1408 base + size <= PAGE_SIZE,
1409 ("vm_page_bits: illegal base/size %d/%d", base, size)
1412 if (size == 0) /* handle degenerate case */
1415 first_bit = base >> DEV_BSHIFT;
1416 last_bit = (base + size - 1) >> DEV_BSHIFT;
1418 return ((2 << last_bit) - (1 << first_bit));
1422 * Sets portions of a page valid and clean. The arguments are expected
1423 * to be DEV_BSIZE aligned but if they aren't the bitmap is inclusive
1424 * of any partial chunks touched by the range. The invalid portion of
1425 * such chunks will be zero'd.
1427 * This routine may not block.
1429 * (base + size) must be less then or equal to PAGE_SIZE.
1432 vm_page_set_validclean(vm_page_t m, int base, int size)
1438 if (size == 0) /* handle degenerate case */
1442 * If the base is not DEV_BSIZE aligned and the valid
1443 * bit is clear, we have to zero out a portion of the
1447 if ((frag = base & ~(DEV_BSIZE - 1)) != base &&
1448 (m->valid & (1 << (base >> DEV_BSHIFT))) == 0
1450 pmap_zero_page_area(
1458 * If the ending offset is not DEV_BSIZE aligned and the
1459 * valid bit is clear, we have to zero out a portion of
1463 endoff = base + size;
1465 if ((frag = endoff & ~(DEV_BSIZE - 1)) != endoff &&
1466 (m->valid & (1 << (endoff >> DEV_BSHIFT))) == 0
1468 pmap_zero_page_area(
1471 DEV_BSIZE - (endoff & (DEV_BSIZE - 1))
1476 * Set valid, clear dirty bits. If validating the entire
1477 * page we can safely clear the pmap modify bit. We also
1478 * use this opportunity to clear the PG_NOSYNC flag. If a process
1479 * takes a write fault on a MAP_NOSYNC memory area the flag will
1482 * We set valid bits inclusive of any overlap, but we can only
1483 * clear dirty bits for DEV_BSIZE chunks that are fully within
1487 pagebits = vm_page_bits(base, size);
1488 m->valid |= pagebits;
1490 if ((frag = base & (DEV_BSIZE - 1)) != 0) {
1491 frag = DEV_BSIZE - frag;
1497 pagebits = vm_page_bits(base, size & (DEV_BSIZE - 1));
1499 m->dirty &= ~pagebits;
1500 if (base == 0 && size == PAGE_SIZE) {
1501 pmap_clear_modify(m);
1502 vm_page_flag_clear(m, PG_NOSYNC);
1507 vm_page_clear_dirty(vm_page_t m, int base, int size)
1509 m->dirty &= ~vm_page_bits(base, size);
1513 * Make the page all-dirty.
1515 * Also make sure the related object and vnode reflect the fact that the
1516 * object may now contain a dirty page.
1519 vm_page_dirty(vm_page_t m)
1522 int pqtype = m->queue - m->pc;
1524 KASSERT(pqtype != PQ_CACHE && pqtype != PQ_FREE,
1525 ("vm_page_dirty: page in free/cache queue!"));
1526 if (m->dirty != VM_PAGE_BITS_ALL) {
1527 m->dirty = VM_PAGE_BITS_ALL;
1529 vm_object_set_writeable_dirty(m->object);
1534 * Invalidates DEV_BSIZE'd chunks within a page. Both the
1535 * valid and dirty bits for the effected areas are cleared.
1540 vm_page_set_invalid(vm_page_t m, int base, int size)
1544 bits = vm_page_bits(base, size);
1547 m->object->generation++;
1551 * The kernel assumes that the invalid portions of a page contain
1552 * garbage, but such pages can be mapped into memory by user code.
1553 * When this occurs, we must zero out the non-valid portions of the
1554 * page so user code sees what it expects.
1556 * Pages are most often semi-valid when the end of a file is mapped
1557 * into memory and the file's size is not page aligned.
1560 vm_page_zero_invalid(vm_page_t m, boolean_t setvalid)
1566 * Scan the valid bits looking for invalid sections that
1567 * must be zerod. Invalid sub-DEV_BSIZE'd areas ( where the
1568 * valid bit may be set ) have already been zerod by
1569 * vm_page_set_validclean().
1571 for (b = i = 0; i <= PAGE_SIZE / DEV_BSIZE; ++i) {
1572 if (i == (PAGE_SIZE / DEV_BSIZE) ||
1573 (m->valid & (1 << i))
1576 pmap_zero_page_area(
1579 (i - b) << DEV_BSHIFT
1587 * setvalid is TRUE when we can safely set the zero'd areas
1588 * as being valid. We can do this if there are no cache consistency
1589 * issues. e.g. it is ok to do with UFS, but not ok to do with NFS.
1592 m->valid = VM_PAGE_BITS_ALL;
1596 * Is a (partial) page valid? Note that the case where size == 0
1597 * will return FALSE in the degenerate case where the page is entirely
1598 * invalid, and TRUE otherwise.
1603 vm_page_is_valid(vm_page_t m, int base, int size)
1605 int bits = vm_page_bits(base, size);
1607 if (m->valid && ((m->valid & bits) == bits))
1614 * update dirty bits from pmap/mmu. May not block.
1617 vm_page_test_dirty(vm_page_t m)
1619 if ((m->dirty != VM_PAGE_BITS_ALL) && pmap_is_modified(m)) {
1625 * Issue an event on a VM page. Corresponding action structures are
1626 * removed from the page's list and called.
1629 vm_page_event_internal(vm_page_t m, vm_page_event_t event)
1631 struct vm_page_action *scan, *next;
1633 LIST_FOREACH_MUTABLE(scan, &m->action_list, entry, next) {
1634 if (scan->event == event) {
1635 scan->event = VMEVENT_NONE;
1636 LIST_REMOVE(scan, entry);
1637 scan->func(m, scan);
1642 #include "opt_ddb.h"
1644 #include <sys/kernel.h>
1646 #include <ddb/ddb.h>
1648 DB_SHOW_COMMAND(page, vm_page_print_page_info)
1650 db_printf("vmstats.v_free_count: %d\n", vmstats.v_free_count);
1651 db_printf("vmstats.v_cache_count: %d\n", vmstats.v_cache_count);
1652 db_printf("vmstats.v_inactive_count: %d\n", vmstats.v_inactive_count);
1653 db_printf("vmstats.v_active_count: %d\n", vmstats.v_active_count);
1654 db_printf("vmstats.v_wire_count: %d\n", vmstats.v_wire_count);
1655 db_printf("vmstats.v_free_reserved: %d\n", vmstats.v_free_reserved);
1656 db_printf("vmstats.v_free_min: %d\n", vmstats.v_free_min);
1657 db_printf("vmstats.v_free_target: %d\n", vmstats.v_free_target);
1658 db_printf("vmstats.v_cache_min: %d\n", vmstats.v_cache_min);
1659 db_printf("vmstats.v_inactive_target: %d\n", vmstats.v_inactive_target);
1662 DB_SHOW_COMMAND(pageq, vm_page_print_pageq_info)
1665 db_printf("PQ_FREE:");
1666 for(i=0;i<PQ_L2_SIZE;i++) {
1667 db_printf(" %d", vm_page_queues[PQ_FREE + i].lcnt);
1671 db_printf("PQ_CACHE:");
1672 for(i=0;i<PQ_L2_SIZE;i++) {
1673 db_printf(" %d", vm_page_queues[PQ_CACHE + i].lcnt);
1677 db_printf("PQ_ACTIVE: %d, PQ_INACTIVE: %d\n",
1678 vm_page_queues[PQ_ACTIVE].lcnt,
1679 vm_page_queues[PQ_INACTIVE].lcnt);