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 1.21 2004/05/13 17:40:19 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.
69 * Resident memory management module.
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 vm_page_t vm_page_select_cache (vm_object_t, vm_pindex_t);
96 * Associated with page of user-allocatable memory is a
100 static struct vm_page **vm_page_buckets; /* Array of buckets */
101 static int vm_page_bucket_count; /* How big is array? */
102 static int vm_page_hash_mask; /* Mask for hash function */
103 static volatile int vm_page_bucket_generation;
105 struct vpgqueues vm_page_queues[PQ_COUNT];
108 vm_page_queue_init(void) {
111 for(i=0;i<PQ_L2_SIZE;i++) {
112 vm_page_queues[PQ_FREE+i].cnt = &vmstats.v_free_count;
114 vm_page_queues[PQ_INACTIVE].cnt = &vmstats.v_inactive_count;
116 vm_page_queues[PQ_ACTIVE].cnt = &vmstats.v_active_count;
117 vm_page_queues[PQ_HOLD].cnt = &vmstats.v_active_count;
118 for(i=0;i<PQ_L2_SIZE;i++) {
119 vm_page_queues[PQ_CACHE+i].cnt = &vmstats.v_cache_count;
121 for(i=0;i<PQ_COUNT;i++) {
122 TAILQ_INIT(&vm_page_queues[i].pl);
126 vm_page_t vm_page_array = 0;
127 int vm_page_array_size = 0;
129 int vm_page_zero_count = 0;
131 static __inline int vm_page_hash (vm_object_t object, vm_pindex_t pindex);
132 static void vm_page_free_wakeup (void);
137 * Sets the page size, perhaps based upon the memory
138 * size. Must be called before any use of page-size
139 * dependent functions.
142 vm_set_page_size(void)
144 if (vmstats.v_page_size == 0)
145 vmstats.v_page_size = PAGE_SIZE;
146 if (((vmstats.v_page_size - 1) & vmstats.v_page_size) != 0)
147 panic("vm_set_page_size: page size not a power of two");
153 * Add a new page to the freelist for use by the system. New pages
154 * are added to both the head and tail of the associated free page
155 * queue in a bottom-up fashion, so both zero'd and non-zero'd page
156 * requests pull 'recent' adds (higher physical addresses) first.
158 * Must be called at splhigh().
161 vm_add_new_page(vm_paddr_t pa)
164 struct vpgqueues *vpq;
166 ++vmstats.v_page_count;
167 ++vmstats.v_free_count;
168 m = PHYS_TO_VM_PAGE(pa);
171 m->pc = (pa >> PAGE_SHIFT) & PQ_L2_MASK;
172 m->queue = m->pc + PQ_FREE;
173 vpq = &vm_page_queues[m->queue];
175 TAILQ_INSERT_TAIL(&vpq->pl, m, pageq);
177 TAILQ_INSERT_HEAD(&vpq->pl, m, pageq);
178 vpq->flipflop = 1 - vpq->flipflop;
179 vm_page_queues[m->queue].lcnt++;
186 * Initializes the resident memory module.
188 * Allocates memory for the page cells, and
189 * for the object/offset-to-page hash table headers.
190 * Each page cell is initialized and placed on the free list.
194 vm_page_startup(vm_offset_t starta, vm_offset_t enda, vm_offset_t vaddr)
197 struct vm_page **bucket;
199 vm_paddr_t page_range;
206 /* the biggest memory array is the second group of pages */
208 vm_paddr_t biggestone, biggestsize;
216 vaddr = round_page(vaddr);
218 for (i = 0; phys_avail[i + 1]; i += 2) {
219 phys_avail[i] = round_page(phys_avail[i]);
220 phys_avail[i + 1] = trunc_page(phys_avail[i + 1]);
223 for (i = 0; phys_avail[i + 1]; i += 2) {
224 vm_paddr_t size = phys_avail[i + 1] - phys_avail[i];
226 if (size > biggestsize) {
234 end = phys_avail[biggestone+1];
237 * Initialize the queue headers for the free queue, the active queue
238 * and the inactive queue.
241 vm_page_queue_init();
244 * Allocate (and initialize) the hash table buckets.
246 * The number of buckets MUST BE a power of 2, and the actual value is
247 * the next power of 2 greater than the number of physical pages in
250 * We make the hash table approximately 2x the number of pages to
251 * reduce the chain length. This is about the same size using the
252 * singly-linked list as the 1x hash table we were using before
253 * using TAILQ but the chain length will be smaller.
255 * Note: This computation can be tweaked if desired.
257 vm_page_buckets = (struct vm_page **)vaddr;
258 bucket = vm_page_buckets;
259 if (vm_page_bucket_count == 0) {
260 vm_page_bucket_count = 1;
261 while (vm_page_bucket_count < atop(total))
262 vm_page_bucket_count <<= 1;
264 vm_page_bucket_count <<= 1;
265 vm_page_hash_mask = vm_page_bucket_count - 1;
268 * Validate these addresses.
270 new_end = end - vm_page_bucket_count * sizeof(struct vm_page *);
271 new_end = trunc_page(new_end);
272 mapped = round_page(vaddr);
273 vaddr = pmap_map(mapped, new_end, end,
274 VM_PROT_READ | VM_PROT_WRITE);
275 vaddr = round_page(vaddr);
276 bzero((caddr_t) mapped, vaddr - mapped);
278 for (i = 0; i < vm_page_bucket_count; i++) {
284 * Compute the number of pages of memory that will be available for
285 * use (taking into account the overhead of a page structure per
289 first_page = phys_avail[0] / PAGE_SIZE;
291 page_range = phys_avail[(nblocks - 1) * 2 + 1] / PAGE_SIZE - first_page;
292 npages = (total - (page_range * sizeof(struct vm_page)) -
293 (end - new_end)) / PAGE_SIZE;
297 * Initialize the mem entry structures now, and put them in the free
300 vm_page_array = (vm_page_t) vaddr;
304 * Validate these addresses.
307 new_end = trunc_page(end - page_range * sizeof(struct vm_page));
308 mapped = pmap_map(mapped, new_end, end,
309 VM_PROT_READ | VM_PROT_WRITE);
312 * Clear all of the page structures
314 bzero((caddr_t) vm_page_array, page_range * sizeof(struct vm_page));
315 vm_page_array_size = page_range;
318 * Construct the free queue(s) in ascending order (by physical
319 * address) so that the first 16MB of physical memory is allocated
320 * last rather than first. On large-memory machines, this avoids
321 * the exhaustion of low physical memory before isa_dmainit has run.
323 vmstats.v_page_count = 0;
324 vmstats.v_free_count = 0;
325 for (i = 0; phys_avail[i + 1] && npages > 0; i += 2) {
330 last_pa = phys_avail[i + 1];
331 while (pa < last_pa && npages-- > 0) {
342 * Distributes the object/offset key pair among hash buckets.
344 * NOTE: This macro depends on vm_page_bucket_count being a power of 2.
345 * This routine may not block.
347 * We try to randomize the hash based on the object to spread the pages
348 * out in the hash table without it costing us too much.
351 vm_page_hash(vm_object_t object, vm_pindex_t pindex)
353 int i = ((uintptr_t)object + pindex) ^ object->hash_rand;
355 return(i & vm_page_hash_mask);
359 vm_page_unhold(vm_page_t mem)
362 KASSERT(mem->hold_count >= 0, ("vm_page_unhold: hold count < 0!!!"));
363 if (mem->hold_count == 0 && mem->queue == PQ_HOLD)
364 vm_page_free_toq(mem);
368 * vm_page_insert: [ internal use only ]
370 * Inserts the given mem entry into the object and object list.
372 * The pagetables are not updated but will presumably fault the page
373 * in if necessary, or if a kernel page the caller will at some point
374 * enter the page into the kernel's pmap. We are not allowed to block
375 * here so we *can't* do this anyway.
377 * This routine may not block.
378 * This routine must be called at splvm().
381 vm_page_insert(vm_page_t m, vm_object_t object, vm_pindex_t pindex)
383 struct vm_page **bucket;
385 if (m->object != NULL)
386 panic("vm_page_insert: already inserted");
389 * Record the object/offset pair in this page
395 * Insert it into the object_object/offset hash table
397 bucket = &vm_page_buckets[vm_page_hash(object, pindex)];
400 vm_page_bucket_generation++;
403 * Now link into the object's list of backed pages.
406 TAILQ_INSERT_TAIL(&object->memq, m, listq);
407 object->generation++;
410 * show that the object has one more resident page.
413 object->resident_page_count++;
416 * Since we are inserting a new and possibly dirty page,
417 * update the object's OBJ_WRITEABLE and OBJ_MIGHTBEDIRTY flags.
419 if (m->flags & PG_WRITEABLE)
420 vm_object_set_writeable_dirty(object);
425 * NOTE: used by device pager as well -wfj
427 * Removes the given mem entry from the object/offset-page
428 * table and the object page list, but do not invalidate/terminate
431 * This routine must be called at splvm()
432 * The underlying pmap entry (if any) is NOT removed here.
433 * This routine may not block.
436 vm_page_remove(vm_page_t m)
440 if (m->object == NULL)
443 if ((m->flags & PG_BUSY) == 0) {
444 panic("vm_page_remove: page not busy");
448 * Basically destroy the page.
456 * Remove from the object_object/offset hash table. The object
457 * must be on the hash queue, we will panic if it isn't
459 * Note: we must NULL-out m->hnext to prevent loops in detached
460 * buffers with vm_page_lookup().
463 struct vm_page **bucket;
465 bucket = &vm_page_buckets[vm_page_hash(m->object, m->pindex)];
466 while (*bucket != m) {
468 panic("vm_page_remove(): page not found in hash");
469 bucket = &(*bucket)->hnext;
473 vm_page_bucket_generation++;
477 * Now remove from the object's list of backed pages.
479 TAILQ_REMOVE(&object->memq, m, listq);
482 * And show that the object has one fewer resident page.
484 object->resident_page_count--;
485 object->generation++;
493 * Locate and return the page at (object, pindex), or NULL if the
494 * page could not be found.
496 * This routine will operate properly without spl protection, but
497 * the returned page could be in flux if it is busy. Because an
498 * interrupt can race a caller's busy check (unbusying and freeing the
499 * page we return before the caller is able to check the busy bit),
500 * the caller should generally call this routine at splvm().
502 * Callers may call this routine without spl protection if they know
503 * 'for sure' that the page will not be ripped out from under them
508 vm_page_lookup(vm_object_t object, vm_pindex_t pindex)
511 struct vm_page **bucket;
515 * Search the hash table for this object/offset pair
519 generation = vm_page_bucket_generation;
520 bucket = &vm_page_buckets[vm_page_hash(object, pindex)];
521 for (m = *bucket; m != NULL; m = m->hnext) {
522 if ((m->object == object) && (m->pindex == pindex)) {
523 if (vm_page_bucket_generation != generation)
528 if (vm_page_bucket_generation != generation)
536 * Move the given memory entry from its
537 * current object to the specified target object/offset.
539 * The object must be locked.
540 * This routine may not block.
542 * Note: this routine will raise itself to splvm(), the caller need not.
544 * Note: swap associated with the page must be invalidated by the move. We
545 * have to do this for several reasons: (1) we aren't freeing the
546 * page, (2) we are dirtying the page, (3) the VM system is probably
547 * moving the page from object A to B, and will then later move
548 * the backing store from A to B and we can't have a conflict.
550 * Note: we *always* dirty the page. It is necessary both for the
551 * fact that we moved it, and because we may be invalidating
552 * swap. If the page is on the cache, we have to deactivate it
553 * or vm_page_dirty() will panic. Dirty pages are not allowed
558 vm_page_rename(vm_page_t m, vm_object_t new_object, vm_pindex_t new_pindex)
564 vm_page_insert(m, new_object, new_pindex);
565 if (m->queue - m->pc == PQ_CACHE)
566 vm_page_deactivate(m);
572 * vm_page_unqueue_nowakeup:
574 * vm_page_unqueue() without any wakeup
576 * This routine must be called at splhigh().
577 * This routine may not block.
581 vm_page_unqueue_nowakeup(vm_page_t m)
583 int queue = m->queue;
584 struct vpgqueues *pq;
585 if (queue != PQ_NONE) {
586 pq = &vm_page_queues[queue];
588 TAILQ_REMOVE(&pq->pl, m, pageq);
597 * Remove a page from its queue.
599 * This routine must be called at splhigh().
600 * This routine may not block.
604 vm_page_unqueue(vm_page_t m)
606 int queue = m->queue;
607 struct vpgqueues *pq;
608 if (queue != PQ_NONE) {
610 pq = &vm_page_queues[queue];
611 TAILQ_REMOVE(&pq->pl, m, pageq);
614 if ((queue - m->pc) == PQ_CACHE) {
615 if (vm_paging_needed())
626 * Find a page on the specified queue with color optimization.
628 * The page coloring optimization attempts to locate a page
629 * that does not overload other nearby pages in the object in
630 * the cpu's L1 or L2 caches. We need this optimization because
631 * cpu caches tend to be physical caches, while object spaces tend
634 * This routine must be called at splvm().
635 * This routine may not block.
637 * This routine may only be called from the vm_page_list_find() macro
641 _vm_page_list_find(int basequeue, int index)
645 struct vpgqueues *pq;
647 pq = &vm_page_queues[basequeue];
650 * Note that for the first loop, index+i and index-i wind up at the
651 * same place. Even though this is not totally optimal, we've already
652 * blown it by missing the cache case so we do not care.
655 for(i = PQ_L2_SIZE / 2; i > 0; --i) {
656 if ((m = TAILQ_FIRST(&pq[(index + i) & PQ_L2_MASK].pl)) != NULL)
659 if ((m = TAILQ_FIRST(&pq[(index - i) & PQ_L2_MASK].pl)) != NULL)
668 * vm_page_select_cache:
670 * Find a page on the cache queue with color optimization. As pages
671 * might be found, but not applicable, they are deactivated. This
672 * keeps us from using potentially busy cached pages.
674 * This routine must be called at splvm().
675 * This routine may not block.
678 vm_page_select_cache(vm_object_t object, vm_pindex_t pindex)
683 m = vm_page_list_find(
685 (pindex + object->pg_color) & PQ_L2_MASK,
688 if (m && ((m->flags & (PG_BUSY|PG_UNMANAGED)) || m->busy ||
689 m->hold_count || m->wire_count)) {
690 vm_page_deactivate(m);
698 * vm_page_select_free:
700 * Find a free or zero page, with specified preference. We attempt to
701 * inline the nominal case and fall back to _vm_page_select_free()
704 * This routine must be called at splvm().
705 * This routine may not block.
708 static __inline vm_page_t
709 vm_page_select_free(vm_object_t object, vm_pindex_t pindex, boolean_t prefer_zero)
713 m = vm_page_list_find(
715 (pindex + object->pg_color) & PQ_L2_MASK,
724 * Allocate and return a memory cell associated
725 * with this VM object/offset pair.
728 * VM_ALLOC_NORMAL allow use of cache pages, nominal free drain
729 * VM_ALLOC_SYSTEM greater free drain
730 * VM_ALLOC_INTERRUPT allow free list to be completely drained
731 * VM_ALLOC_ZERO advisory request for pre-zero'd page
733 * Object must be locked.
734 * This routine may not block.
736 * Additional special handling is required when called from an
737 * interrupt (VM_ALLOC_INTERRUPT). We are not allowed to mess with
738 * the page cache in this case.
742 vm_page_alloc(vm_object_t object, vm_pindex_t pindex, int page_req)
747 KASSERT(!vm_page_lookup(object, pindex),
748 ("vm_page_alloc: page already allocated"));
750 (VM_ALLOC_NORMAL|VM_ALLOC_INTERRUPT|VM_ALLOC_SYSTEM));
753 * The pager is allowed to eat deeper into the free page list.
755 if (curthread == pagethread)
756 page_req |= VM_ALLOC_SYSTEM;
760 if (vmstats.v_free_count > vmstats.v_free_reserved ||
761 ((page_req & VM_ALLOC_INTERRUPT) && vmstats.v_free_count > 0) ||
762 ((page_req & VM_ALLOC_SYSTEM) && vmstats.v_cache_count == 0 &&
763 vmstats.v_free_count > vmstats.v_interrupt_free_min)
766 * The free queue has sufficient free pages to take one out.
768 if (page_req & VM_ALLOC_ZERO)
769 m = vm_page_select_free(object, pindex, TRUE);
771 m = vm_page_select_free(object, pindex, FALSE);
772 } else if (page_req & VM_ALLOC_NORMAL) {
774 * Allocatable from the cache (non-interrupt only). On
775 * success, we must free the page and try again, thus
776 * ensuring that vmstats.v_*_free_min counters are replenished.
779 if (curthread->td_preempted) {
780 printf("vm_page_alloc(): warning, attempt to allocate"
781 " cache page from preempting interrupt\n");
784 m = vm_page_select_cache(object, pindex);
787 m = vm_page_select_cache(object, pindex);
790 * On succuess move the page into the free queue and loop.
793 KASSERT(m->dirty == 0,
794 ("Found dirty cache page %p", m));
796 vm_page_protect(m, VM_PROT_NONE);
802 * On failure return NULL
805 #if defined(DIAGNOSTIC)
806 if (vmstats.v_cache_count > 0)
807 printf("vm_page_alloc(NORMAL): missing pages on cache queue: %d\n", vmstats.v_cache_count);
809 vm_pageout_deficit++;
814 * No pages available, wakeup the pageout daemon and give up.
817 vm_pageout_deficit++;
825 KASSERT(m != NULL, ("vm_page_alloc(): missing page on free queue\n"));
828 * Remove from free queue
830 vm_page_unqueue_nowakeup(m);
833 * Initialize structure. Only the PG_ZERO flag is inherited.
835 if (m->flags & PG_ZERO) {
836 vm_page_zero_count--;
837 m->flags = PG_ZERO | PG_BUSY;
846 KASSERT(m->dirty == 0,
847 ("vm_page_alloc: free/cache page %p was dirty", m));
850 * vm_page_insert() is safe prior to the splx(). Note also that
851 * inserting a page here does not insert it into the pmap (which
852 * could cause us to block allocating memory). We cannot block
855 vm_page_insert(m, object, pindex);
858 * Don't wakeup too often - wakeup the pageout daemon when
859 * we would be nearly out of memory.
861 if (vm_paging_needed())
869 * vm_wait: (also see VM_WAIT macro)
871 * Block until free pages are available for allocation
872 * - Called in various places before memory allocations.
881 if (curthread == pagethread) {
882 vm_pageout_pages_needed = 1;
883 tsleep(&vm_pageout_pages_needed, 0, "VMWait", 0);
885 if (!vm_pages_needed) {
887 wakeup(&vm_pages_needed);
889 tsleep(&vmstats.v_free_count, 0, "vmwait", 0);
895 * vm_waitpfault: (also see VM_WAITPFAULT macro)
897 * Block until free pages are available for allocation
898 * - Called only in vm_fault so that processes page faulting
899 * can be easily tracked.
900 * - Sleeps at a lower priority than vm_wait() so that vm_wait()ing
901 * processes will be able to grab memory first. Do not change
902 * this balance without careful testing first.
911 if (!vm_pages_needed) {
913 wakeup(&vm_pages_needed);
915 tsleep(&vmstats.v_free_count, 0, "pfault", 0);
922 * Put the specified page on the active list (if appropriate).
923 * Ensure that act_count is at least ACT_INIT but do not otherwise
926 * The page queues must be locked.
927 * This routine may not block.
930 vm_page_activate(vm_page_t m)
935 if (m->queue != PQ_ACTIVE) {
936 if ((m->queue - m->pc) == PQ_CACHE)
937 mycpu->gd_cnt.v_reactivated++;
941 if (m->wire_count == 0 && (m->flags & PG_UNMANAGED) == 0) {
942 m->queue = PQ_ACTIVE;
943 vm_page_queues[PQ_ACTIVE].lcnt++;
944 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, m, pageq);
945 if (m->act_count < ACT_INIT)
946 m->act_count = ACT_INIT;
947 vmstats.v_active_count++;
950 if (m->act_count < ACT_INIT)
951 m->act_count = ACT_INIT;
958 * vm_page_free_wakeup:
960 * Helper routine for vm_page_free_toq() and vm_page_cache(). This
961 * routine is called when a page has been added to the cache or free
964 * This routine may not block.
965 * This routine must be called at splvm()
968 vm_page_free_wakeup(void)
971 * if pageout daemon needs pages, then tell it that there are
974 if (vm_pageout_pages_needed &&
975 vmstats.v_cache_count + vmstats.v_free_count >= vmstats.v_pageout_free_min) {
976 wakeup(&vm_pageout_pages_needed);
977 vm_pageout_pages_needed = 0;
980 * wakeup processes that are waiting on memory if we hit a
981 * high water mark. And wakeup scheduler process if we have
982 * lots of memory. this process will swapin processes.
984 if (vm_pages_needed && !vm_page_count_min()) {
986 wakeup(&vmstats.v_free_count);
993 * Returns the given page to the PQ_FREE list,
994 * disassociating it with any VM object.
996 * Object and page must be locked prior to entry.
997 * This routine may not block.
1001 vm_page_free_toq(vm_page_t m)
1004 struct vpgqueues *pq;
1006 vm_object_t object = m->object;
1011 mycpu->gd_cnt.v_tfree++;
1013 if (m->busy || ((m->queue - m->pc) == PQ_FREE)) {
1015 "vm_page_free: pindex(%lu), busy(%d), PG_BUSY(%d), hold(%d)\n",
1016 (u_long)m->pindex, m->busy, (m->flags & PG_BUSY) ? 1 : 0,
1018 if ((m->queue - m->pc) == PQ_FREE)
1019 panic("vm_page_free: freeing free page");
1021 panic("vm_page_free: freeing busy page");
1025 * unqueue, then remove page. Note that we cannot destroy
1026 * the page here because we do not want to call the pager's
1027 * callback routine until after we've put the page on the
1028 * appropriate free queue.
1031 vm_page_unqueue_nowakeup(m);
1035 * If fictitious remove object association and
1036 * return, otherwise delay object association removal.
1039 if ((m->flags & PG_FICTITIOUS) != 0) {
1047 if (m->wire_count != 0) {
1048 if (m->wire_count > 1) {
1049 panic("vm_page_free: invalid wire count (%d), pindex: 0x%lx",
1050 m->wire_count, (long)m->pindex);
1052 panic("vm_page_free: freeing wired page");
1056 * We used to free the underlying vnode if the object was empty,
1057 * but we no longer do that because it can block. Instead, the
1058 * sync code is made responsible for the cleanup.
1062 (object->type == OBJT_VNODE) &&
1063 ((object->flags & OBJ_DEAD) == 0) &&
1064 object->handle != NULL
1066 struct vnode *vp = (struct vnode *)object->handle;
1068 if (vp && VSHOULDFREE(vp))
1074 * Clear the UNMANAGED flag when freeing an unmanaged page.
1077 if (m->flags & PG_UNMANAGED) {
1078 m->flags &= ~PG_UNMANAGED;
1081 pmap_page_is_free(m);
1085 if (m->hold_count != 0) {
1086 m->flags &= ~PG_ZERO;
1089 m->queue = PQ_FREE + m->pc;
1090 pq = &vm_page_queues[m->queue];
1095 * Put zero'd pages on the end ( where we look for zero'd pages
1096 * first ) and non-zerod pages at the head.
1099 if (m->flags & PG_ZERO) {
1100 TAILQ_INSERT_TAIL(&pq->pl, m, pageq);
1101 ++vm_page_zero_count;
1103 TAILQ_INSERT_HEAD(&pq->pl, m, pageq);
1106 vm_page_free_wakeup();
1114 * Prevent PV management from being done on the page. The page is
1115 * removed from the paging queues as if it were wired, and as a
1116 * consequence of no longer being managed the pageout daemon will not
1117 * touch it (since there is no way to locate the pte mappings for the
1118 * page). madvise() calls that mess with the pmap will also no longer
1119 * operate on the page.
1121 * Beyond that the page is still reasonably 'normal'. Freeing the page
1122 * will clear the flag.
1124 * This routine is used by OBJT_PHYS objects - objects using unswappable
1125 * physical memory as backing store rather then swap-backed memory and
1126 * will eventually be extended to support 4MB unmanaged physical
1131 vm_page_unmanage(vm_page_t m)
1136 if ((m->flags & PG_UNMANAGED) == 0) {
1137 if (m->wire_count == 0)
1140 vm_page_flag_set(m, PG_UNMANAGED);
1147 * Mark this page as wired down by yet
1148 * another map, removing it from paging queues
1151 * The page queues must be locked.
1152 * This routine may not block.
1155 vm_page_wire(vm_page_t m)
1160 * Only bump the wire statistics if the page is not already wired,
1161 * and only unqueue the page if it is on some queue (if it is unmanaged
1162 * it is already off the queues).
1165 if (m->wire_count == 0) {
1166 if ((m->flags & PG_UNMANAGED) == 0)
1168 vmstats.v_wire_count++;
1171 KASSERT(m->wire_count != 0,
1172 ("vm_page_wire: wire_count overflow m=%p", m));
1175 vm_page_flag_set(m, PG_MAPPED);
1181 * Release one wiring of this page, potentially
1182 * enabling it to be paged again.
1184 * Many pages placed on the inactive queue should actually go
1185 * into the cache, but it is difficult to figure out which. What
1186 * we do instead, if the inactive target is well met, is to put
1187 * clean pages at the head of the inactive queue instead of the tail.
1188 * This will cause them to be moved to the cache more quickly and
1189 * if not actively re-referenced, freed more quickly. If we just
1190 * stick these pages at the end of the inactive queue, heavy filesystem
1191 * meta-data accesses can cause an unnecessary paging load on memory bound
1192 * processes. This optimization causes one-time-use metadata to be
1193 * reused more quickly.
1195 * BUT, if we are in a low-memory situation we have no choice but to
1196 * put clean pages on the cache queue.
1198 * A number of routines use vm_page_unwire() to guarantee that the page
1199 * will go into either the inactive or active queues, and will NEVER
1200 * be placed in the cache - for example, just after dirtying a page.
1201 * dirty pages in the cache are not allowed.
1203 * The page queues must be locked.
1204 * This routine may not block.
1207 vm_page_unwire(vm_page_t m, int activate)
1213 if (m->wire_count > 0) {
1215 if (m->wire_count == 0) {
1216 vmstats.v_wire_count--;
1217 if (m->flags & PG_UNMANAGED) {
1219 } else if (activate) {
1220 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_ACTIVE].pl, m, pageq);
1221 m->queue = PQ_ACTIVE;
1222 vm_page_queues[PQ_ACTIVE].lcnt++;
1223 vmstats.v_active_count++;
1225 vm_page_flag_clear(m, PG_WINATCFLS);
1226 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_INACTIVE].pl, m, pageq);
1227 m->queue = PQ_INACTIVE;
1228 vm_page_queues[PQ_INACTIVE].lcnt++;
1229 vmstats.v_inactive_count++;
1233 panic("vm_page_unwire: invalid wire count: %d", m->wire_count);
1240 * Move the specified page to the inactive queue. If the page has
1241 * any associated swap, the swap is deallocated.
1243 * Normally athead is 0 resulting in LRU operation. athead is set
1244 * to 1 if we want this page to be 'as if it were placed in the cache',
1245 * except without unmapping it from the process address space.
1247 * This routine may not block.
1249 static __inline void
1250 _vm_page_deactivate(vm_page_t m, int athead)
1255 * Ignore if already inactive.
1257 if (m->queue == PQ_INACTIVE)
1261 if (m->wire_count == 0 && (m->flags & PG_UNMANAGED) == 0) {
1262 if ((m->queue - m->pc) == PQ_CACHE)
1263 mycpu->gd_cnt.v_reactivated++;
1264 vm_page_flag_clear(m, PG_WINATCFLS);
1267 TAILQ_INSERT_HEAD(&vm_page_queues[PQ_INACTIVE].pl, m, pageq);
1269 TAILQ_INSERT_TAIL(&vm_page_queues[PQ_INACTIVE].pl, m, pageq);
1270 m->queue = PQ_INACTIVE;
1271 vm_page_queues[PQ_INACTIVE].lcnt++;
1272 vmstats.v_inactive_count++;
1278 vm_page_deactivate(vm_page_t m)
1280 _vm_page_deactivate(m, 0);
1284 * vm_page_try_to_cache:
1286 * Returns 0 on failure, 1 on success
1289 vm_page_try_to_cache(vm_page_t m)
1291 if (m->dirty || m->hold_count || m->busy || m->wire_count ||
1292 (m->flags & (PG_BUSY|PG_UNMANAGED))) {
1295 vm_page_test_dirty(m);
1303 * vm_page_try_to_free()
1305 * Attempt to free the page. If we cannot free it, we do nothing.
1306 * 1 is returned on success, 0 on failure.
1310 vm_page_try_to_free(vm_page_t m)
1312 if (m->dirty || m->hold_count || m->busy || m->wire_count ||
1313 (m->flags & (PG_BUSY|PG_UNMANAGED))) {
1316 vm_page_test_dirty(m);
1320 vm_page_protect(m, VM_PROT_NONE);
1329 * Put the specified page onto the page cache queue (if appropriate).
1331 * This routine may not block.
1334 vm_page_cache(vm_page_t m)
1338 if ((m->flags & (PG_BUSY|PG_UNMANAGED)) || m->busy ||
1339 m->wire_count || m->hold_count) {
1340 printf("vm_page_cache: attempting to cache busy/held page\n");
1343 if ((m->queue - m->pc) == PQ_CACHE)
1347 * Remove all pmaps and indicate that the page is not
1348 * writeable or mapped.
1351 vm_page_protect(m, VM_PROT_NONE);
1352 if (m->dirty != 0) {
1353 panic("vm_page_cache: caching a dirty page, pindex: %ld",
1357 vm_page_unqueue_nowakeup(m);
1358 m->queue = PQ_CACHE + m->pc;
1359 vm_page_queues[m->queue].lcnt++;
1360 TAILQ_INSERT_TAIL(&vm_page_queues[m->queue].pl, m, pageq);
1361 vmstats.v_cache_count++;
1362 vm_page_free_wakeup();
1369 * Cache, deactivate, or do nothing as appropriate. This routine
1370 * is typically used by madvise() MADV_DONTNEED.
1372 * Generally speaking we want to move the page into the cache so
1373 * it gets reused quickly. However, this can result in a silly syndrome
1374 * due to the page recycling too quickly. Small objects will not be
1375 * fully cached. On the otherhand, if we move the page to the inactive
1376 * queue we wind up with a problem whereby very large objects
1377 * unnecessarily blow away our inactive and cache queues.
1379 * The solution is to move the pages based on a fixed weighting. We
1380 * either leave them alone, deactivate them, or move them to the cache,
1381 * where moving them to the cache has the highest weighting.
1382 * By forcing some pages into other queues we eventually force the
1383 * system to balance the queues, potentially recovering other unrelated
1384 * space from active. The idea is to not force this to happen too
1389 vm_page_dontneed(vm_page_t m)
1391 static int dnweight;
1398 * occassionally leave the page alone
1401 if ((dnw & 0x01F0) == 0 ||
1402 m->queue == PQ_INACTIVE ||
1403 m->queue - m->pc == PQ_CACHE
1405 if (m->act_count >= ACT_INIT)
1411 vm_page_test_dirty(m);
1413 if (m->dirty || (dnw & 0x0070) == 0) {
1415 * Deactivate the page 3 times out of 32.
1420 * Cache the page 28 times out of every 32. Note that
1421 * the page is deactivated instead of cached, but placed
1422 * at the head of the queue instead of the tail.
1426 _vm_page_deactivate(m, head);
1430 * Grab a page, blocking if it is busy and allocating a page if necessary.
1431 * A busy page is returned or NULL.
1433 * If VM_ALLOC_RETRY is specified VM_ALLOC_NORMAL must also be specified.
1434 * If VM_ALLOC_RETRY is not specified
1436 * This routine may block, but if VM_ALLOC_RETRY is not set then NULL is
1437 * always returned if we had blocked.
1438 * This routine will never return NULL if VM_ALLOC_RETRY is set.
1439 * This routine may not be called from an interrupt.
1440 * The returned page may not be entirely valid.
1442 * This routine may be called from mainline code without spl protection and
1443 * be guarenteed a busied page associated with the object at the specified
1447 vm_page_grab(vm_object_t object, vm_pindex_t pindex, int allocflags)
1452 KKASSERT(allocflags &
1453 (VM_ALLOC_NORMAL|VM_ALLOC_INTERRUPT|VM_ALLOC_SYSTEM));
1456 if ((m = vm_page_lookup(object, pindex)) != NULL) {
1457 if (m->busy || (m->flags & PG_BUSY)) {
1458 generation = object->generation;
1460 while ((object->generation == generation) &&
1461 (m->busy || (m->flags & PG_BUSY))) {
1462 vm_page_flag_set(m, PG_WANTED | PG_REFERENCED);
1463 tsleep(m, 0, "pgrbwt", 0);
1464 if ((allocflags & VM_ALLOC_RETRY) == 0) {
1475 m = vm_page_alloc(object, pindex, allocflags & ~VM_ALLOC_RETRY);
1478 if ((allocflags & VM_ALLOC_RETRY) == 0)
1488 * Mapping function for valid bits or for dirty bits in
1489 * a page. May not block.
1491 * Inputs are required to range within a page.
1495 vm_page_bits(int base, int size)
1501 base + size <= PAGE_SIZE,
1502 ("vm_page_bits: illegal base/size %d/%d", base, size)
1505 if (size == 0) /* handle degenerate case */
1508 first_bit = base >> DEV_BSHIFT;
1509 last_bit = (base + size - 1) >> DEV_BSHIFT;
1511 return ((2 << last_bit) - (1 << first_bit));
1515 * vm_page_set_validclean:
1517 * Sets portions of a page valid and clean. The arguments are expected
1518 * to be DEV_BSIZE aligned but if they aren't the bitmap is inclusive
1519 * of any partial chunks touched by the range. The invalid portion of
1520 * such chunks will be zero'd.
1522 * This routine may not block.
1524 * (base + size) must be less then or equal to PAGE_SIZE.
1527 vm_page_set_validclean(vm_page_t m, int base, int size)
1533 if (size == 0) /* handle degenerate case */
1537 * If the base is not DEV_BSIZE aligned and the valid
1538 * bit is clear, we have to zero out a portion of the
1542 if ((frag = base & ~(DEV_BSIZE - 1)) != base &&
1543 (m->valid & (1 << (base >> DEV_BSHIFT))) == 0
1545 pmap_zero_page_area(
1553 * If the ending offset is not DEV_BSIZE aligned and the
1554 * valid bit is clear, we have to zero out a portion of
1558 endoff = base + size;
1560 if ((frag = endoff & ~(DEV_BSIZE - 1)) != endoff &&
1561 (m->valid & (1 << (endoff >> DEV_BSHIFT))) == 0
1563 pmap_zero_page_area(
1566 DEV_BSIZE - (endoff & (DEV_BSIZE - 1))
1571 * Set valid, clear dirty bits. If validating the entire
1572 * page we can safely clear the pmap modify bit. We also
1573 * use this opportunity to clear the PG_NOSYNC flag. If a process
1574 * takes a write fault on a MAP_NOSYNC memory area the flag will
1577 * We set valid bits inclusive of any overlap, but we can only
1578 * clear dirty bits for DEV_BSIZE chunks that are fully within
1582 pagebits = vm_page_bits(base, size);
1583 m->valid |= pagebits;
1585 if ((frag = base & (DEV_BSIZE - 1)) != 0) {
1586 frag = DEV_BSIZE - frag;
1592 pagebits = vm_page_bits(base, size & (DEV_BSIZE - 1));
1594 m->dirty &= ~pagebits;
1595 if (base == 0 && size == PAGE_SIZE) {
1596 pmap_clear_modify(m);
1597 vm_page_flag_clear(m, PG_NOSYNC);
1604 vm_page_set_dirty(vm_page_t m, int base, int size)
1606 m->dirty |= vm_page_bits(base, size);
1612 vm_page_clear_dirty(vm_page_t m, int base, int size)
1614 m->dirty &= ~vm_page_bits(base, size);
1618 * vm_page_set_invalid:
1620 * Invalidates DEV_BSIZE'd chunks within a page. Both the
1621 * valid and dirty bits for the effected areas are cleared.
1626 vm_page_set_invalid(vm_page_t m, int base, int size)
1630 bits = vm_page_bits(base, size);
1633 m->object->generation++;
1637 * vm_page_zero_invalid()
1639 * The kernel assumes that the invalid portions of a page contain
1640 * garbage, but such pages can be mapped into memory by user code.
1641 * When this occurs, we must zero out the non-valid portions of the
1642 * page so user code sees what it expects.
1644 * Pages are most often semi-valid when the end of a file is mapped
1645 * into memory and the file's size is not page aligned.
1649 vm_page_zero_invalid(vm_page_t m, boolean_t setvalid)
1655 * Scan the valid bits looking for invalid sections that
1656 * must be zerod. Invalid sub-DEV_BSIZE'd areas ( where the
1657 * valid bit may be set ) have already been zerod by
1658 * vm_page_set_validclean().
1661 for (b = i = 0; i <= PAGE_SIZE / DEV_BSIZE; ++i) {
1662 if (i == (PAGE_SIZE / DEV_BSIZE) ||
1663 (m->valid & (1 << i))
1666 pmap_zero_page_area(
1669 (i - b) << DEV_BSHIFT
1677 * setvalid is TRUE when we can safely set the zero'd areas
1678 * as being valid. We can do this if there are no cache consistency
1679 * issues. e.g. it is ok to do with UFS, but not ok to do with NFS.
1683 m->valid = VM_PAGE_BITS_ALL;
1689 * Is (partial) page valid? Note that the case where size == 0
1690 * will return FALSE in the degenerate case where the page is
1691 * entirely invalid, and TRUE otherwise.
1697 vm_page_is_valid(vm_page_t m, int base, int size)
1699 int bits = vm_page_bits(base, size);
1701 if (m->valid && ((m->valid & bits) == bits))
1708 * update dirty bits from pmap/mmu. May not block.
1712 vm_page_test_dirty(vm_page_t m)
1714 if ((m->dirty != VM_PAGE_BITS_ALL) && pmap_is_modified(m)) {
1719 #include "opt_ddb.h"
1721 #include <sys/kernel.h>
1723 #include <ddb/ddb.h>
1725 DB_SHOW_COMMAND(page, vm_page_print_page_info)
1727 db_printf("vmstats.v_free_count: %d\n", vmstats.v_free_count);
1728 db_printf("vmstats.v_cache_count: %d\n", vmstats.v_cache_count);
1729 db_printf("vmstats.v_inactive_count: %d\n", vmstats.v_inactive_count);
1730 db_printf("vmstats.v_active_count: %d\n", vmstats.v_active_count);
1731 db_printf("vmstats.v_wire_count: %d\n", vmstats.v_wire_count);
1732 db_printf("vmstats.v_free_reserved: %d\n", vmstats.v_free_reserved);
1733 db_printf("vmstats.v_free_min: %d\n", vmstats.v_free_min);
1734 db_printf("vmstats.v_free_target: %d\n", vmstats.v_free_target);
1735 db_printf("vmstats.v_cache_min: %d\n", vmstats.v_cache_min);
1736 db_printf("vmstats.v_inactive_target: %d\n", vmstats.v_inactive_target);
1739 DB_SHOW_COMMAND(pageq, vm_page_print_pageq_info)
1742 db_printf("PQ_FREE:");
1743 for(i=0;i<PQ_L2_SIZE;i++) {
1744 db_printf(" %d", vm_page_queues[PQ_FREE + i].lcnt);
1748 db_printf("PQ_CACHE:");
1749 for(i=0;i<PQ_L2_SIZE;i++) {
1750 db_printf(" %d", vm_page_queues[PQ_CACHE + i].lcnt);
1754 db_printf("PQ_ACTIVE: %d, PQ_INACTIVE: %d\n",
1755 vm_page_queues[PQ_ACTIVE].lcnt,
1756 vm_page_queues[PQ_INACTIVE].lcnt);