2 * Copyright (c) 1991, 1993
3 * The Regents of the University of California. All rights reserved.
4 * Copyright (c) 1994 John S. Dyson
6 * Copyright (c) 1994 David Greenman
10 * This code is derived from software contributed to Berkeley by
11 * The Mach Operating System project at Carnegie-Mellon University.
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
16 * 1. Redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer.
18 * 2. Redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution.
21 * 3. All advertising materials mentioning features or use of this software
22 * must display the following acknowledgement:
23 * This product includes software developed by the University of
24 * California, Berkeley and its contributors.
25 * 4. Neither the name of the University nor the names of its contributors
26 * may be used to endorse or promote products derived from this software
27 * without specific prior written permission.
29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
41 * from: @(#)vm_fault.c 8.4 (Berkeley) 1/12/94
44 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
45 * All rights reserved.
47 * Authors: Avadis Tevanian, Jr., Michael Wayne Young
49 * Permission to use, copy, modify and distribute this software and
50 * its documentation is hereby granted, provided that both the copyright
51 * notice and this permission notice appear in all copies of the
52 * software, derivative works or modified versions, and any portions
53 * thereof, and that both notices appear in supporting documentation.
55 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
56 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
57 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
59 * Carnegie Mellon requests users of this software to return to
61 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
62 * School of Computer Science
63 * Carnegie Mellon University
64 * Pittsburgh PA 15213-3890
66 * any improvements or extensions that they make and grant Carnegie the
67 * rights to redistribute these changes.
69 * $FreeBSD: src/sys/vm/vm_fault.c,v 1.108.2.8 2002/02/26 05:49:27 silby Exp $
70 * $DragonFly: src/sys/vm/vm_fault.c,v 1.47 2008/07/01 02:02:56 dillon Exp $
74 * Page fault handling module.
77 #include <sys/param.h>
78 #include <sys/systm.h>
79 #include <sys/kernel.h>
81 #include <sys/vnode.h>
82 #include <sys/resourcevar.h>
83 #include <sys/vmmeter.h>
84 #include <sys/vkernel.h>
85 #include <sys/sfbuf.h>
87 #include <sys/sysctl.h>
90 #include <vm/vm_param.h>
92 #include <vm/vm_map.h>
93 #include <vm/vm_object.h>
94 #include <vm/vm_page.h>
95 #include <vm/vm_pageout.h>
96 #include <vm/vm_kern.h>
97 #include <vm/vm_pager.h>
98 #include <vm/vnode_pager.h>
99 #include <vm/vm_extern.h>
101 #include <sys/thread2.h>
102 #include <vm/vm_page2.h>
110 vm_object_t first_object;
111 vm_prot_t first_prot;
113 vm_map_entry_t entry;
114 int lookup_still_valid;
123 static int vm_fast_fault = 1;
124 SYSCTL_INT(_vm, OID_AUTO, fast_fault, CTLFLAG_RW, &vm_fast_fault, 0, "");
125 static int debug_cluster = 0;
126 SYSCTL_INT(_vm, OID_AUTO, debug_cluster, CTLFLAG_RW, &debug_cluster, 0, "");
128 static int vm_fault_object(struct faultstate *, vm_pindex_t, vm_prot_t);
129 static int vm_fault_vpagetable(struct faultstate *, vm_pindex_t *, vpte_t, int);
131 static int vm_fault_additional_pages (vm_page_t, int, int, vm_page_t *, int *);
133 static int vm_fault_ratelimit(struct vmspace *);
134 static void vm_prefault(pmap_t pmap, vm_offset_t addra, vm_map_entry_t entry,
138 release_page(struct faultstate *fs)
140 vm_page_deactivate(fs->m);
141 vm_page_wakeup(fs->m);
146 unlock_map(struct faultstate *fs)
148 if (fs->lookup_still_valid && fs->map) {
149 vm_map_lookup_done(fs->map, fs->entry, 0);
150 fs->lookup_still_valid = FALSE;
155 * Clean up after a successful call to vm_fault_object() so another call
156 * to vm_fault_object() can be made.
159 _cleanup_successful_fault(struct faultstate *fs, int relock)
161 if (fs->object != fs->first_object) {
162 vm_page_free(fs->first_m);
163 vm_object_pip_wakeup(fs->object);
166 fs->object = fs->first_object;
167 if (relock && fs->lookup_still_valid == FALSE) {
169 vm_map_lock_read(fs->map);
170 fs->lookup_still_valid = TRUE;
175 _unlock_things(struct faultstate *fs, int dealloc)
177 vm_object_pip_wakeup(fs->first_object);
178 _cleanup_successful_fault(fs, 0);
180 vm_object_deallocate(fs->first_object);
181 fs->first_object = NULL;
184 if (fs->vp != NULL) {
190 #define unlock_things(fs) _unlock_things(fs, 0)
191 #define unlock_and_deallocate(fs) _unlock_things(fs, 1)
192 #define cleanup_successful_fault(fs) _cleanup_successful_fault(fs, 1)
197 * Determine if the pager for the current object *might* contain the page.
199 * We only need to try the pager if this is not a default object (default
200 * objects are zero-fill and have no real pager), and if we are not taking
201 * a wiring fault or if the FS entry is wired.
203 #define TRYPAGER(fs) \
204 (fs->object->type != OBJT_DEFAULT && \
205 (((fs->fault_flags & VM_FAULT_WIRE_MASK) == 0) || fs->wired))
210 * Handle a page fault occuring at the given address, requiring the given
211 * permissions, in the map specified. If successful, the page is inserted
212 * into the associated physical map.
214 * NOTE: The given address should be truncated to the proper page address.
216 * KERN_SUCCESS is returned if the page fault is handled; otherwise,
217 * a standard error specifying why the fault is fatal is returned.
219 * The map in question must be referenced, and remains so.
220 * The caller may hold no locks.
223 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, int fault_flags)
226 vm_pindex_t first_pindex;
227 struct faultstate fs;
230 mycpu->gd_cnt.v_vm_faults++;
234 fs.fault_flags = fault_flags;
239 * Find the vm_map_entry representing the backing store and resolve
240 * the top level object and page index. This may have the side
241 * effect of executing a copy-on-write on the map entry and/or
242 * creating a shadow object, but will not COW any actual VM pages.
244 * On success fs.map is left read-locked and various other fields
245 * are initialized but not otherwise referenced or locked.
247 * NOTE! vm_map_lookup will try to upgrade the fault_type to
248 * VM_FAULT_WRITE if the map entry is a virtual page table and also
249 * writable, so we can set the 'A'accessed bit in the virtual page
253 result = vm_map_lookup(&fs.map, vaddr, fault_type,
254 &fs.entry, &fs.first_object,
255 &first_pindex, &fs.first_prot, &fs.wired);
258 * If the lookup failed or the map protections are incompatible,
259 * the fault generally fails. However, if the caller is trying
260 * to do a user wiring we have more work to do.
262 if (result != KERN_SUCCESS) {
263 if (result != KERN_PROTECTION_FAILURE ||
264 (fs.fault_flags & VM_FAULT_WIRE_MASK) != VM_FAULT_USER_WIRE)
266 if (result == KERN_INVALID_ADDRESS && growstack &&
267 map != &kernel_map && curproc != NULL) {
268 result = vm_map_growstack(curproc, vaddr);
269 if (result != KERN_SUCCESS)
270 return (KERN_FAILURE);
278 * If we are user-wiring a r/w segment, and it is COW, then
279 * we need to do the COW operation. Note that we don't
280 * currently COW RO sections now, because it is NOT desirable
281 * to COW .text. We simply keep .text from ever being COW'ed
282 * and take the heat that one cannot debug wired .text sections.
284 result = vm_map_lookup(&fs.map, vaddr,
285 VM_PROT_READ|VM_PROT_WRITE|
286 VM_PROT_OVERRIDE_WRITE,
287 &fs.entry, &fs.first_object,
288 &first_pindex, &fs.first_prot,
290 if (result != KERN_SUCCESS)
294 * If we don't COW now, on a user wire, the user will never
295 * be able to write to the mapping. If we don't make this
296 * restriction, the bookkeeping would be nearly impossible.
298 if ((fs.entry->protection & VM_PROT_WRITE) == 0)
299 fs.entry->max_protection &= ~VM_PROT_WRITE;
303 * fs.map is read-locked
305 * Misc checks. Save the map generation number to detect races.
307 fs.map_generation = fs.map->timestamp;
309 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
310 panic("vm_fault: fault on nofault entry, addr: %lx",
315 * A system map entry may return a NULL object. No object means
316 * no pager means an unrecoverable kernel fault.
318 if (fs.first_object == NULL) {
319 panic("vm_fault: unrecoverable fault at %p in entry %p",
320 (void *)vaddr, fs.entry);
324 * Make a reference to this object to prevent its disposal while we
325 * are messing with it. Once we have the reference, the map is free
326 * to be diddled. Since objects reference their shadows (and copies),
327 * they will stay around as well.
329 * Bump the paging-in-progress count to prevent size changes (e.g.
330 * truncation operations) during I/O. This must be done after
331 * obtaining the vnode lock in order to avoid possible deadlocks.
333 vm_object_reference(fs.first_object);
334 fs.vp = vnode_pager_lock(fs.first_object);
335 vm_object_pip_add(fs.first_object, 1);
337 fs.lookup_still_valid = TRUE;
339 fs.object = fs.first_object; /* so unlock_and_deallocate works */
342 * If the entry is wired we cannot change the page protection.
345 fault_type = fs.first_prot;
348 * The page we want is at (first_object, first_pindex), but if the
349 * vm_map_entry is VM_MAPTYPE_VPAGETABLE we have to traverse the
350 * page table to figure out the actual pindex.
352 * NOTE! DEVELOPMENT IN PROGRESS, THIS IS AN INITIAL IMPLEMENTATION
355 if (fs.entry->maptype == VM_MAPTYPE_VPAGETABLE) {
356 result = vm_fault_vpagetable(&fs, &first_pindex,
357 fs.entry->aux.master_pde,
359 if (result == KERN_TRY_AGAIN)
361 if (result != KERN_SUCCESS)
366 * Now we have the actual (object, pindex), fault in the page. If
367 * vm_fault_object() fails it will unlock and deallocate the FS
368 * data. If it succeeds everything remains locked and fs->object
369 * will have an additinal PIP count if it is not equal to
372 * vm_fault_object will set fs->prot for the pmap operation. It is
373 * allowed to set VM_PROT_WRITE if fault_type == VM_PROT_READ if the
374 * page can be safely written. However, it will force a read-only
375 * mapping for a read fault if the memory is managed by a virtual
378 result = vm_fault_object(&fs, first_pindex, fault_type);
380 if (result == KERN_TRY_AGAIN)
382 if (result != KERN_SUCCESS)
386 * On success vm_fault_object() does not unlock or deallocate, and fs.m
387 * will contain a busied page.
389 * Enter the page into the pmap and do pmap-related adjustments.
391 pmap_enter(fs.map->pmap, vaddr, fs.m, fs.prot, fs.wired);
394 * Burst in a few more pages if possible. The fs.map should still
397 if (fault_flags & VM_FAULT_BURST) {
398 if ((fs.fault_flags & VM_FAULT_WIRE_MASK) == 0 &&
400 vm_prefault(fs.map->pmap, vaddr, fs.entry, fs.prot);
405 vm_page_flag_clear(fs.m, PG_ZERO);
406 vm_page_flag_set(fs.m, PG_REFERENCED);
409 * If the page is not wired down, then put it where the pageout daemon
412 if (fs.fault_flags & VM_FAULT_WIRE_MASK) {
416 vm_page_unwire(fs.m, 1);
418 vm_page_activate(fs.m);
421 if (curthread->td_lwp) {
423 curthread->td_lwp->lwp_ru.ru_majflt++;
425 curthread->td_lwp->lwp_ru.ru_minflt++;
430 * Unlock everything, and return
432 vm_page_wakeup(fs.m);
433 vm_object_deallocate(fs.first_object);
435 return (KERN_SUCCESS);
439 * Fault in the specified virtual address in the current process map,
440 * returning a held VM page or NULL. See vm_fault_page() for more
444 vm_fault_page_quick(vm_offset_t va, vm_prot_t fault_type, int *errorp)
446 struct lwp *lp = curthread->td_lwp;
449 m = vm_fault_page(&lp->lwp_vmspace->vm_map, va,
450 fault_type, VM_FAULT_NORMAL, errorp);
455 * Fault in the specified virtual address in the specified map, doing all
456 * necessary manipulation of the object store and all necessary I/O. Return
457 * a held VM page or NULL, and set *errorp. The related pmap is not
460 * The returned page will be properly dirtied if VM_PROT_WRITE was specified,
461 * and marked PG_REFERENCED as well.
463 * If the page cannot be faulted writable and VM_PROT_WRITE was specified, an
464 * error will be returned.
467 vm_fault_page(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
468 int fault_flags, int *errorp)
470 vm_pindex_t first_pindex;
471 struct faultstate fs;
473 vm_prot_t orig_fault_type = fault_type;
475 mycpu->gd_cnt.v_vm_faults++;
479 fs.fault_flags = fault_flags;
480 KKASSERT((fault_flags & VM_FAULT_WIRE_MASK) == 0);
484 * Find the vm_map_entry representing the backing store and resolve
485 * the top level object and page index. This may have the side
486 * effect of executing a copy-on-write on the map entry and/or
487 * creating a shadow object, but will not COW any actual VM pages.
489 * On success fs.map is left read-locked and various other fields
490 * are initialized but not otherwise referenced or locked.
492 * NOTE! vm_map_lookup will upgrade the fault_type to VM_FAULT_WRITE
493 * if the map entry is a virtual page table and also writable,
494 * so we can set the 'A'accessed bit in the virtual page table entry.
497 result = vm_map_lookup(&fs.map, vaddr, fault_type,
498 &fs.entry, &fs.first_object,
499 &first_pindex, &fs.first_prot, &fs.wired);
501 if (result != KERN_SUCCESS) {
507 * fs.map is read-locked
509 * Misc checks. Save the map generation number to detect races.
511 fs.map_generation = fs.map->timestamp;
513 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
514 panic("vm_fault: fault on nofault entry, addr: %lx",
519 * A system map entry may return a NULL object. No object means
520 * no pager means an unrecoverable kernel fault.
522 if (fs.first_object == NULL) {
523 panic("vm_fault: unrecoverable fault at %p in entry %p",
524 (void *)vaddr, fs.entry);
528 * Make a reference to this object to prevent its disposal while we
529 * are messing with it. Once we have the reference, the map is free
530 * to be diddled. Since objects reference their shadows (and copies),
531 * they will stay around as well.
533 * Bump the paging-in-progress count to prevent size changes (e.g.
534 * truncation operations) during I/O. This must be done after
535 * obtaining the vnode lock in order to avoid possible deadlocks.
537 vm_object_reference(fs.first_object);
538 fs.vp = vnode_pager_lock(fs.first_object);
539 vm_object_pip_add(fs.first_object, 1);
541 fs.lookup_still_valid = TRUE;
543 fs.object = fs.first_object; /* so unlock_and_deallocate works */
546 * If the entry is wired we cannot change the page protection.
549 fault_type = fs.first_prot;
552 * The page we want is at (first_object, first_pindex), but if the
553 * vm_map_entry is VM_MAPTYPE_VPAGETABLE we have to traverse the
554 * page table to figure out the actual pindex.
556 * NOTE! DEVELOPMENT IN PROGRESS, THIS IS AN INITIAL IMPLEMENTATION
559 if (fs.entry->maptype == VM_MAPTYPE_VPAGETABLE) {
560 result = vm_fault_vpagetable(&fs, &first_pindex,
561 fs.entry->aux.master_pde,
563 if (result == KERN_TRY_AGAIN)
565 if (result != KERN_SUCCESS) {
572 * Now we have the actual (object, pindex), fault in the page. If
573 * vm_fault_object() fails it will unlock and deallocate the FS
574 * data. If it succeeds everything remains locked and fs->object
575 * will have an additinal PIP count if it is not equal to
578 result = vm_fault_object(&fs, first_pindex, fault_type);
580 if (result == KERN_TRY_AGAIN)
582 if (result != KERN_SUCCESS) {
587 if ((orig_fault_type & VM_PROT_WRITE) &&
588 (fs.prot & VM_PROT_WRITE) == 0) {
589 *errorp = KERN_PROTECTION_FAILURE;
590 unlock_and_deallocate(&fs);
595 * On success vm_fault_object() does not unlock or deallocate, and fs.m
596 * will contain a busied page.
601 * Return a held page. We are not doing any pmap manipulation so do
602 * not set PG_MAPPED. However, adjust the page flags according to
603 * the fault type because the caller may not use a managed pmapping
604 * (so we don't want to lose the fact that the page will be dirtied
605 * if a write fault was specified).
608 vm_page_flag_clear(fs.m, PG_ZERO);
609 if (fault_type & VM_PROT_WRITE)
613 * Update the pmap. We really only have to do this if a COW
614 * occured to replace the read-only page with the new page. For
615 * now just do it unconditionally. XXX
617 pmap_enter(fs.map->pmap, vaddr, fs.m, fs.prot, fs.wired);
618 vm_page_flag_set(fs.m, PG_REFERENCED);
621 * Unbusy the page by activating it. It remains held and will not
624 vm_page_activate(fs.m);
626 if (curthread->td_lwp) {
628 curthread->td_lwp->lwp_ru.ru_majflt++;
630 curthread->td_lwp->lwp_ru.ru_minflt++;
635 * Unlock everything, and return the held page.
637 vm_page_wakeup(fs.m);
638 vm_object_deallocate(fs.first_object);
645 * Fault in the specified (object,offset), dirty the returned page as
646 * needed. If the requested fault_type cannot be done NULL and an
650 vm_fault_object_page(vm_object_t object, vm_ooffset_t offset,
651 vm_prot_t fault_type, int fault_flags, int *errorp)
654 vm_pindex_t first_pindex;
655 struct faultstate fs;
656 struct vm_map_entry entry;
658 bzero(&entry, sizeof(entry));
659 entry.object.vm_object = object;
660 entry.maptype = VM_MAPTYPE_NORMAL;
661 entry.protection = entry.max_protection = fault_type;
665 fs.fault_flags = fault_flags;
667 KKASSERT((fault_flags & VM_FAULT_WIRE_MASK) == 0);
671 fs.first_object = object;
672 first_pindex = OFF_TO_IDX(offset);
674 fs.first_prot = fault_type;
676 /*fs.map_generation = 0; unused */
679 * Make a reference to this object to prevent its disposal while we
680 * are messing with it. Once we have the reference, the map is free
681 * to be diddled. Since objects reference their shadows (and copies),
682 * they will stay around as well.
684 * Bump the paging-in-progress count to prevent size changes (e.g.
685 * truncation operations) during I/O. This must be done after
686 * obtaining the vnode lock in order to avoid possible deadlocks.
688 vm_object_reference(fs.first_object);
689 fs.vp = vnode_pager_lock(fs.first_object);
690 vm_object_pip_add(fs.first_object, 1);
692 fs.lookup_still_valid = TRUE;
694 fs.object = fs.first_object; /* so unlock_and_deallocate works */
697 /* XXX future - ability to operate on VM object using vpagetable */
698 if (fs.entry->maptype == VM_MAPTYPE_VPAGETABLE) {
699 result = vm_fault_vpagetable(&fs, &first_pindex,
700 fs.entry->aux.master_pde,
702 if (result == KERN_TRY_AGAIN)
704 if (result != KERN_SUCCESS) {
712 * Now we have the actual (object, pindex), fault in the page. If
713 * vm_fault_object() fails it will unlock and deallocate the FS
714 * data. If it succeeds everything remains locked and fs->object
715 * will have an additinal PIP count if it is not equal to
718 result = vm_fault_object(&fs, first_pindex, fault_type);
720 if (result == KERN_TRY_AGAIN)
722 if (result != KERN_SUCCESS) {
727 if ((fault_type & VM_PROT_WRITE) && (fs.prot & VM_PROT_WRITE) == 0) {
728 *errorp = KERN_PROTECTION_FAILURE;
729 unlock_and_deallocate(&fs);
734 * On success vm_fault_object() does not unlock or deallocate, and fs.m
735 * will contain a busied page.
740 * Return a held page. We are not doing any pmap manipulation so do
741 * not set PG_MAPPED. However, adjust the page flags according to
742 * the fault type because the caller may not use a managed pmapping
743 * (so we don't want to lose the fact that the page will be dirtied
744 * if a write fault was specified).
747 vm_page_flag_clear(fs.m, PG_ZERO);
748 if (fault_type & VM_PROT_WRITE)
752 * Indicate that the page was accessed.
754 vm_page_flag_set(fs.m, PG_REFERENCED);
757 * Unbusy the page by activating it. It remains held and will not
760 vm_page_activate(fs.m);
762 if (curthread->td_lwp) {
764 mycpu->gd_cnt.v_vm_faults++;
765 curthread->td_lwp->lwp_ru.ru_majflt++;
767 curthread->td_lwp->lwp_ru.ru_minflt++;
772 * Unlock everything, and return the held page.
774 vm_page_wakeup(fs.m);
775 vm_object_deallocate(fs.first_object);
782 * Translate the virtual page number (first_pindex) that is relative
783 * to the address space into a logical page number that is relative to the
784 * backing object. Use the virtual page table pointed to by (vpte).
786 * This implements an N-level page table. Any level can terminate the
787 * scan by setting VPTE_PS. A linear mapping is accomplished by setting
788 * VPTE_PS in the master page directory entry set via mcontrol(MADV_SETMAP).
792 vm_fault_vpagetable(struct faultstate *fs, vm_pindex_t *pindex,
793 vpte_t vpte, int fault_type)
796 int vshift = 32 - PAGE_SHIFT; /* page index bits remaining */
797 int result = KERN_SUCCESS;
802 * We cannot proceed if the vpte is not valid, not readable
803 * for a read fault, or not writable for a write fault.
805 if ((vpte & VPTE_V) == 0) {
806 unlock_and_deallocate(fs);
807 return (KERN_FAILURE);
809 if ((fault_type & VM_PROT_READ) && (vpte & VPTE_R) == 0) {
810 unlock_and_deallocate(fs);
811 return (KERN_FAILURE);
813 if ((fault_type & VM_PROT_WRITE) && (vpte & VPTE_W) == 0) {
814 unlock_and_deallocate(fs);
815 return (KERN_FAILURE);
817 if ((vpte & VPTE_PS) || vshift == 0)
819 KKASSERT(vshift >= VPTE_PAGE_BITS);
822 * Get the page table page. Nominally we only read the page
823 * table, but since we are actively setting VPTE_M and VPTE_A,
824 * tell vm_fault_object() that we are writing it.
826 * There is currently no real need to optimize this.
828 result = vm_fault_object(fs, vpte >> PAGE_SHIFT,
829 VM_PROT_READ|VM_PROT_WRITE);
830 if (result != KERN_SUCCESS)
834 * Process the returned fs.m and look up the page table
835 * entry in the page table page.
837 vshift -= VPTE_PAGE_BITS;
838 sf = sf_buf_alloc(fs->m, SFB_CPUPRIVATE);
839 ptep = ((vpte_t *)sf_buf_kva(sf) +
840 ((*pindex >> vshift) & VPTE_PAGE_MASK));
844 * Page table write-back. If the vpte is valid for the
845 * requested operation, do a write-back to the page table.
847 * XXX VPTE_M is not set properly for page directory pages.
848 * It doesn't get set in the page directory if the page table
849 * is modified during a read access.
851 if ((fault_type & VM_PROT_WRITE) && (vpte & VPTE_V) &&
853 if ((vpte & (VPTE_M|VPTE_A)) != (VPTE_M|VPTE_A)) {
854 atomic_set_int(ptep, VPTE_M|VPTE_A);
855 vm_page_dirty(fs->m);
858 if ((fault_type & VM_PROT_READ) && (vpte & VPTE_V) &&
860 if ((vpte & VPTE_A) == 0) {
861 atomic_set_int(ptep, VPTE_A);
862 vm_page_dirty(fs->m);
866 vm_page_flag_set(fs->m, PG_REFERENCED);
867 vm_page_activate(fs->m);
868 vm_page_wakeup(fs->m);
869 cleanup_successful_fault(fs);
872 * Combine remaining address bits with the vpte.
874 *pindex = (vpte >> PAGE_SHIFT) +
875 (*pindex & ((1 << vshift) - 1));
876 return (KERN_SUCCESS);
881 * Do all operations required to fault-in (fs.first_object, pindex). Run
882 * through the shadow chain as necessary and do required COW or virtual
883 * copy operations. The caller has already fully resolved the vm_map_entry
884 * and, if appropriate, has created a copy-on-write layer. All we need to
885 * do is iterate the object chain.
887 * On failure (fs) is unlocked and deallocated and the caller may return or
888 * retry depending on the failure code. On success (fs) is NOT unlocked or
889 * deallocated, fs.m will contained a resolved, busied page, and fs.object
890 * will have an additional PIP count if it is not equal to fs.first_object.
894 vm_fault_object(struct faultstate *fs,
895 vm_pindex_t first_pindex, vm_prot_t fault_type)
897 vm_object_t next_object;
900 fs->prot = fs->first_prot;
901 fs->object = fs->first_object;
902 pindex = first_pindex;
905 * If a read fault occurs we try to make the page writable if
906 * possible. There are three cases where we cannot make the
907 * page mapping writable:
909 * (1) The mapping is read-only or the VM object is read-only,
910 * fs->prot above will simply not have VM_PROT_WRITE set.
912 * (2) If the mapping is a virtual page table we need to be able
913 * to detect writes so we can set VPTE_M in the virtual page
916 * (3) If the VM page is read-only or copy-on-write, upgrading would
917 * just result in an unnecessary COW fault.
919 * VM_PROT_VPAGED is set if faulting via a virtual page table and
920 * causes adjustments to the 'M'odify bit to also turn off write
921 * access to force a re-fault.
923 if (fs->entry->maptype == VM_MAPTYPE_VPAGETABLE) {
924 if ((fault_type & VM_PROT_WRITE) == 0)
925 fs->prot &= ~VM_PROT_WRITE;
930 * If the object is dead, we stop here
932 if (fs->object->flags & OBJ_DEAD) {
933 unlock_and_deallocate(fs);
934 return (KERN_PROTECTION_FAILURE);
938 * See if page is resident. spl protection is required
939 * to avoid an interrupt unbusy/free race against our
940 * lookup. We must hold the protection through a page
941 * allocation or busy.
944 fs->m = vm_page_lookup(fs->object, pindex);
948 * Wait/Retry if the page is busy. We have to do this
949 * if the page is busy via either PG_BUSY or
950 * vm_page_t->busy because the vm_pager may be using
951 * vm_page_t->busy for pageouts ( and even pageins if
952 * it is the vnode pager ), and we could end up trying
953 * to pagein and pageout the same page simultaneously.
955 * We can theoretically allow the busy case on a read
956 * fault if the page is marked valid, but since such
957 * pages are typically already pmap'd, putting that
958 * special case in might be more effort then it is
959 * worth. We cannot under any circumstances mess
960 * around with a vm_page_t->busy page except, perhaps,
963 if ((fs->m->flags & PG_BUSY) || fs->m->busy) {
965 vm_page_sleep_busy(fs->m, TRUE, "vmpfw");
966 mycpu->gd_cnt.v_intrans++;
967 vm_object_deallocate(fs->first_object);
968 fs->first_object = NULL;
970 return (KERN_TRY_AGAIN);
974 * If reactivating a page from PQ_CACHE we may have
977 queue = fs->m->queue;
978 vm_page_unqueue_nowakeup(fs->m);
980 if ((queue - fs->m->pc) == PQ_CACHE &&
981 vm_page_count_severe()) {
982 vm_page_activate(fs->m);
983 unlock_and_deallocate(fs);
986 return (KERN_TRY_AGAIN);
990 * Mark page busy for other processes, and the
991 * pagedaemon. If it still isn't completely valid
992 * (readable), or if a read-ahead-mark is set on
993 * the VM page, jump to readrest, else we found the
994 * page and can return.
996 * We can release the spl once we have marked the
1002 if (fs->m->object != &kernel_object) {
1003 if ((fs->m->valid & VM_PAGE_BITS_ALL) !=
1007 if (fs->m->flags & PG_RAM) {
1010 vm_page_flag_clear(fs->m, PG_RAM);
1014 break; /* break to PAGE HAS BEEN FOUND */
1018 * Page is not resident, If this is the search termination
1019 * or the pager might contain the page, allocate a new page.
1021 * NOTE: We are still in a critical section.
1023 if (TRYPAGER(fs) || fs->object == fs->first_object) {
1025 * If the page is beyond the object size we fail
1027 if (pindex >= fs->object->size) {
1029 unlock_and_deallocate(fs);
1030 return (KERN_PROTECTION_FAILURE);
1036 if (fs->didlimit == 0 && curproc != NULL) {
1039 limticks = vm_fault_ratelimit(curproc->p_vmspace);
1042 unlock_and_deallocate(fs);
1043 tsleep(curproc, 0, "vmrate", limticks);
1045 return (KERN_TRY_AGAIN);
1050 * Allocate a new page for this object/offset pair.
1053 if (!vm_page_count_severe()) {
1054 fs->m = vm_page_alloc(fs->object, pindex,
1055 (fs->vp || fs->object->backing_object) ? VM_ALLOC_NORMAL : VM_ALLOC_NORMAL | VM_ALLOC_ZERO);
1057 if (fs->m == NULL) {
1059 unlock_and_deallocate(fs);
1061 return (KERN_TRY_AGAIN);
1068 * We have found an invalid or partially valid page, a
1069 * page with a read-ahead mark which might be partially or
1070 * fully valid (and maybe dirty too), or we have allocated
1073 * Attempt to fault-in the page if there is a chance that the
1074 * pager has it, and potentially fault in additional pages
1077 * We are NOT in splvm here and if TRYPAGER is true then
1078 * fs.m will be non-NULL and will be PG_BUSY for us.
1083 u_char behavior = vm_map_entry_behavior(fs->entry);
1085 if (behavior == MAP_ENTRY_BEHAV_RANDOM)
1091 * If sequential access is detected then attempt
1092 * to deactivate/cache pages behind the scan to
1093 * prevent resource hogging.
1095 * Use of PG_RAM to detect sequential access
1096 * also simulates multi-zone sequential access
1097 * detection for free.
1099 * NOTE: Partially valid dirty pages cannot be
1100 * deactivated without causing NFS picemeal
1103 if ((fs->first_object->type != OBJT_DEVICE) &&
1104 (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL ||
1105 (behavior != MAP_ENTRY_BEHAV_RANDOM &&
1106 (fs->m->flags & PG_RAM)))
1108 vm_pindex_t scan_pindex;
1109 int scan_count = 16;
1111 if (first_pindex < 16) {
1115 scan_pindex = first_pindex - 16;
1116 if (scan_pindex < 16)
1117 scan_count = scan_pindex;
1123 while (scan_count) {
1126 mt = vm_page_lookup(fs->first_object,
1129 (mt->valid != VM_PAGE_BITS_ALL)) {
1133 (mt->flags & (PG_BUSY | PG_FICTITIOUS | PG_UNMANAGED)) ||
1139 vm_page_test_dirty(mt);
1144 vm_page_deactivate(mt);
1159 * Avoid deadlocking against the map when doing I/O.
1160 * fs.object and the page is PG_BUSY'd.
1165 * Acquire the page data. We still hold a ref on
1166 * fs.object and the page has been PG_BUSY's.
1168 * The pager may replace the page (for example, in
1169 * order to enter a fictitious page into the
1170 * object). If it does so it is responsible for
1171 * cleaning up the passed page and properly setting
1172 * the new page PG_BUSY.
1174 * If we got here through a PG_RAM read-ahead
1175 * mark the page may be partially dirty and thus
1176 * not freeable. Don't bother checking to see
1177 * if the pager has the page because we can't free
1178 * it anyway. We have to depend on the get_page
1179 * operation filling in any gaps whether there is
1180 * backing store or not.
1182 rv = vm_pager_get_page(fs->object, &fs->m, seqaccess);
1184 if (rv == VM_PAGER_OK) {
1186 * Relookup in case pager changed page. Pager
1187 * is responsible for disposition of old page
1190 * XXX other code segments do relookups too.
1191 * It's a bad abstraction that needs to be
1194 fs->m = vm_page_lookup(fs->object, pindex);
1195 if (fs->m == NULL) {
1196 unlock_and_deallocate(fs);
1197 return (KERN_TRY_AGAIN);
1201 break; /* break to PAGE HAS BEEN FOUND */
1205 * Remove the bogus page (which does not exist at this
1206 * object/offset); before doing so, we must get back
1207 * our object lock to preserve our invariant.
1209 * Also wake up any other process that may want to bring
1212 * If this is the top-level object, we must leave the
1213 * busy page to prevent another process from rushing
1214 * past us, and inserting the page in that object at
1215 * the same time that we are.
1217 if (rv == VM_PAGER_ERROR) {
1219 kprintf("vm_fault: pager read error, pid %d (%s)\n", curproc->p_pid, curproc->p_comm);
1221 kprintf("vm_fault: pager read error, thread %p (%s)\n", curthread, curproc->p_comm);
1225 * Data outside the range of the pager or an I/O error
1227 * The page may have been wired during the pagein,
1228 * e.g. by the buffer cache, and cannot simply be
1229 * freed. Call vnode_pager_freepage() to deal with it.
1232 * XXX - the check for kernel_map is a kludge to work
1233 * around having the machine panic on a kernel space
1234 * fault w/ I/O error.
1236 if (((fs->map != &kernel_map) &&
1237 (rv == VM_PAGER_ERROR)) || (rv == VM_PAGER_BAD)) {
1238 vnode_pager_freepage(fs->m);
1240 unlock_and_deallocate(fs);
1241 if (rv == VM_PAGER_ERROR)
1242 return (KERN_FAILURE);
1244 return (KERN_PROTECTION_FAILURE);
1247 if (fs->object != fs->first_object) {
1248 vnode_pager_freepage(fs->m);
1251 * XXX - we cannot just fall out at this
1252 * point, m has been freed and is invalid!
1258 * We get here if the object has a default pager (or unwiring)
1259 * or the pager doesn't have the page.
1261 if (fs->object == fs->first_object)
1262 fs->first_m = fs->m;
1265 * Move on to the next object. Lock the next object before
1266 * unlocking the current one.
1268 pindex += OFF_TO_IDX(fs->object->backing_object_offset);
1269 next_object = fs->object->backing_object;
1270 if (next_object == NULL) {
1272 * If there's no object left, fill the page in the top
1273 * object with zeros.
1275 if (fs->object != fs->first_object) {
1276 vm_object_pip_wakeup(fs->object);
1278 fs->object = fs->first_object;
1279 pindex = first_pindex;
1280 fs->m = fs->first_m;
1285 * Zero the page if necessary and mark it valid.
1287 if ((fs->m->flags & PG_ZERO) == 0) {
1288 vm_page_zero_fill(fs->m);
1290 mycpu->gd_cnt.v_ozfod++;
1292 mycpu->gd_cnt.v_zfod++;
1293 fs->m->valid = VM_PAGE_BITS_ALL;
1294 break; /* break to PAGE HAS BEEN FOUND */
1296 if (fs->object != fs->first_object) {
1297 vm_object_pip_wakeup(fs->object);
1299 KASSERT(fs->object != next_object, ("object loop %p", next_object));
1300 fs->object = next_object;
1301 vm_object_pip_add(fs->object, 1);
1306 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
1309 * If the page is being written, but isn't already owned by the
1310 * top-level object, we have to copy it into a new page owned by the
1313 KASSERT((fs->m->flags & PG_BUSY) != 0,
1314 ("vm_fault: not busy after main loop"));
1316 if (fs->object != fs->first_object) {
1318 * We only really need to copy if we want to write it.
1320 if (fault_type & VM_PROT_WRITE) {
1322 * This allows pages to be virtually copied from a
1323 * backing_object into the first_object, where the
1324 * backing object has no other refs to it, and cannot
1325 * gain any more refs. Instead of a bcopy, we just
1326 * move the page from the backing object to the
1327 * first object. Note that we must mark the page
1328 * dirty in the first object so that it will go out
1329 * to swap when needed.
1333 * Map, if present, has not changed
1336 fs->map_generation == fs->map->timestamp) &&
1338 * Only one shadow object
1340 (fs->object->shadow_count == 1) &&
1342 * No COW refs, except us
1344 (fs->object->ref_count == 1) &&
1346 * No one else can look this object up
1348 (fs->object->handle == NULL) &&
1350 * No other ways to look the object up
1352 ((fs->object->type == OBJT_DEFAULT) ||
1353 (fs->object->type == OBJT_SWAP)) &&
1355 * We don't chase down the shadow chain
1357 (fs->object == fs->first_object->backing_object) &&
1360 * grab the lock if we need to
1362 (fs->lookup_still_valid ||
1364 lockmgr(&fs->map->lock, LK_EXCLUSIVE|LK_NOWAIT) == 0)
1367 fs->lookup_still_valid = 1;
1369 * get rid of the unnecessary page
1371 vm_page_protect(fs->first_m, VM_PROT_NONE);
1372 vm_page_free(fs->first_m);
1376 * grab the page and put it into the
1377 * process'es object. The page is
1378 * automatically made dirty.
1380 vm_page_rename(fs->m, fs->first_object, first_pindex);
1381 fs->first_m = fs->m;
1382 vm_page_busy(fs->first_m);
1384 mycpu->gd_cnt.v_cow_optim++;
1387 * Oh, well, lets copy it.
1389 vm_page_copy(fs->m, fs->first_m);
1390 vm_page_event(fs->m, VMEVENT_COW);
1395 * We no longer need the old page or object.
1401 * fs->object != fs->first_object due to above
1404 vm_object_pip_wakeup(fs->object);
1407 * Only use the new page below...
1410 mycpu->gd_cnt.v_cow_faults++;
1411 fs->m = fs->first_m;
1412 fs->object = fs->first_object;
1413 pindex = first_pindex;
1416 * If it wasn't a write fault avoid having to copy
1417 * the page by mapping it read-only.
1419 fs->prot &= ~VM_PROT_WRITE;
1424 * We may have had to unlock a map to do I/O. If we did then
1425 * lookup_still_valid will be FALSE. If the map generation count
1426 * also changed then all sorts of things could have happened while
1427 * we were doing the I/O and we need to retry.
1430 if (!fs->lookup_still_valid &&
1432 (fs->map->timestamp != fs->map_generation)) {
1434 unlock_and_deallocate(fs);
1435 return (KERN_TRY_AGAIN);
1439 * If the fault is a write, we know that this page is being
1440 * written NOW so dirty it explicitly to save on pmap_is_modified()
1443 * If this is a NOSYNC mmap we do not want to set PG_NOSYNC
1444 * if the page is already dirty to prevent data written with
1445 * the expectation of being synced from not being synced.
1446 * Likewise if this entry does not request NOSYNC then make
1447 * sure the page isn't marked NOSYNC. Applications sharing
1448 * data should use the same flags to avoid ping ponging.
1450 * Also tell the backing pager, if any, that it should remove
1451 * any swap backing since the page is now dirty.
1453 if (fs->prot & VM_PROT_WRITE) {
1454 vm_object_set_writeable_dirty(fs->m->object);
1455 if (fs->entry->eflags & MAP_ENTRY_NOSYNC) {
1456 if (fs->m->dirty == 0)
1457 vm_page_flag_set(fs->m, PG_NOSYNC);
1459 vm_page_flag_clear(fs->m, PG_NOSYNC);
1461 if (fs->fault_flags & VM_FAULT_DIRTY) {
1463 vm_page_dirty(fs->m);
1464 swap_pager_unswapped(fs->m);
1470 * Page had better still be busy. We are still locked up and
1471 * fs->object will have another PIP reference if it is not equal
1472 * to fs->first_object.
1474 KASSERT(fs->m->flags & PG_BUSY,
1475 ("vm_fault: page %p not busy!", fs->m));
1478 * Sanity check: page must be completely valid or it is not fit to
1479 * map into user space. vm_pager_get_pages() ensures this.
1481 if (fs->m->valid != VM_PAGE_BITS_ALL) {
1482 vm_page_zero_invalid(fs->m, TRUE);
1483 kprintf("Warning: page %p partially invalid on fault\n", fs->m);
1486 return (KERN_SUCCESS);
1490 * Wire down a range of virtual addresses in a map. The entry in question
1491 * should be marked in-transition and the map must be locked. We must
1492 * release the map temporarily while faulting-in the page to avoid a
1493 * deadlock. Note that the entry may be clipped while we are blocked but
1494 * will never be freed.
1497 vm_fault_wire(vm_map_t map, vm_map_entry_t entry, boolean_t user_wire)
1499 boolean_t fictitious;
1507 pmap = vm_map_pmap(map);
1508 start = entry->start;
1510 fictitious = entry->object.vm_object &&
1511 (entry->object.vm_object->type == OBJT_DEVICE);
1517 * We simulate a fault to get the page and enter it in the physical
1520 for (va = start; va < end; va += PAGE_SIZE) {
1522 rv = vm_fault(map, va, VM_PROT_READ,
1523 VM_FAULT_USER_WIRE);
1525 rv = vm_fault(map, va, VM_PROT_READ|VM_PROT_WRITE,
1526 VM_FAULT_CHANGE_WIRING);
1529 while (va > start) {
1531 if ((pa = pmap_extract(pmap, va)) == 0)
1533 pmap_change_wiring(pmap, va, FALSE);
1535 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1);
1542 return (KERN_SUCCESS);
1546 * Unwire a range of virtual addresses in a map. The map should be
1550 vm_fault_unwire(vm_map_t map, vm_map_entry_t entry)
1552 boolean_t fictitious;
1559 pmap = vm_map_pmap(map);
1560 start = entry->start;
1562 fictitious = entry->object.vm_object &&
1563 (entry->object.vm_object->type == OBJT_DEVICE);
1566 * Since the pages are wired down, we must be able to get their
1567 * mappings from the physical map system.
1569 for (va = start; va < end; va += PAGE_SIZE) {
1570 pa = pmap_extract(pmap, va);
1572 pmap_change_wiring(pmap, va, FALSE);
1574 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1);
1580 * Reduce the rate at which memory is allocated to a process based
1581 * on the perceived load on the VM system. As the load increases
1582 * the allocation burst rate goes down and the delay increases.
1584 * Rate limiting does not apply when faulting active or inactive
1585 * pages. When faulting 'cache' pages, rate limiting only applies
1586 * if the system currently has a severe page deficit.
1588 * XXX vm_pagesupply should be increased when a page is freed.
1590 * We sleep up to 1/10 of a second.
1593 vm_fault_ratelimit(struct vmspace *vmspace)
1595 if (vm_load_enable == 0)
1597 if (vmspace->vm_pagesupply > 0) {
1598 --vmspace->vm_pagesupply;
1602 if (vm_load_debug) {
1603 kprintf("load %-4d give %d pgs, wait %d, pid %-5d (%s)\n",
1605 (1000 - vm_load ) / 10, vm_load * hz / 10000,
1606 curproc->p_pid, curproc->p_comm);
1609 vmspace->vm_pagesupply = (1000 - vm_load) / 10;
1610 return(vm_load * hz / 10000);
1615 * vm_fault_copy_entry
1617 * Copy all of the pages from a wired-down map entry to another.
1619 * In/out conditions:
1620 * The source and destination maps must be locked for write.
1621 * The source map entry must be wired down (or be a sharing map
1622 * entry corresponding to a main map entry that is wired down).
1626 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
1627 vm_map_entry_t dst_entry, vm_map_entry_t src_entry)
1629 vm_object_t dst_object;
1630 vm_object_t src_object;
1631 vm_ooffset_t dst_offset;
1632 vm_ooffset_t src_offset;
1642 src_object = src_entry->object.vm_object;
1643 src_offset = src_entry->offset;
1646 * Create the top-level object for the destination entry. (Doesn't
1647 * actually shadow anything - we copy the pages directly.)
1649 vm_map_entry_allocate_object(dst_entry);
1650 dst_object = dst_entry->object.vm_object;
1652 prot = dst_entry->max_protection;
1655 * Loop through all of the pages in the entry's range, copying each
1656 * one from the source object (it should be there) to the destination
1659 for (vaddr = dst_entry->start, dst_offset = 0;
1660 vaddr < dst_entry->end;
1661 vaddr += PAGE_SIZE, dst_offset += PAGE_SIZE) {
1664 * Allocate a page in the destination object
1667 dst_m = vm_page_alloc(dst_object,
1668 OFF_TO_IDX(dst_offset), VM_ALLOC_NORMAL);
1669 if (dst_m == NULL) {
1672 } while (dst_m == NULL);
1675 * Find the page in the source object, and copy it in.
1676 * (Because the source is wired down, the page will be in
1679 src_m = vm_page_lookup(src_object,
1680 OFF_TO_IDX(dst_offset + src_offset));
1682 panic("vm_fault_copy_wired: page missing");
1684 vm_page_copy(src_m, dst_m);
1685 vm_page_event(src_m, VMEVENT_COW);
1688 * Enter it in the pmap...
1691 vm_page_flag_clear(dst_m, PG_ZERO);
1692 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, FALSE);
1695 * Mark it no longer busy, and put it on the active list.
1697 vm_page_activate(dst_m);
1698 vm_page_wakeup(dst_m);
1705 * This routine checks around the requested page for other pages that
1706 * might be able to be faulted in. This routine brackets the viable
1707 * pages for the pages to be paged in.
1710 * m, rbehind, rahead
1713 * marray (array of vm_page_t), reqpage (index of requested page)
1716 * number of pages in marray
1719 vm_fault_additional_pages(vm_page_t m, int rbehind, int rahead,
1720 vm_page_t *marray, int *reqpage)
1724 vm_pindex_t pindex, startpindex, endpindex, tpindex;
1726 int cbehind, cahead;
1732 * we don't fault-ahead for device pager
1734 if (object->type == OBJT_DEVICE) {
1741 * if the requested page is not available, then give up now
1743 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) {
1744 *reqpage = 0; /* not used by caller, fix compiler warn */
1748 if ((cbehind == 0) && (cahead == 0)) {
1754 if (rahead > cahead) {
1758 if (rbehind > cbehind) {
1763 * Do not do any readahead if we have insufficient free memory.
1765 * XXX code was broken disabled before and has instability
1766 * with this conditonal fixed, so shortcut for now.
1768 if (burst_fault == 0 || vm_page_count_severe()) {
1775 * scan backward for the read behind pages -- in memory
1777 * Assume that if the page is not found an interrupt will not
1778 * create it. Theoretically interrupts can only remove (busy)
1779 * pages, not create new associations.
1782 if (rbehind > pindex) {
1786 startpindex = pindex - rbehind;
1790 for (tpindex = pindex; tpindex > startpindex; --tpindex) {
1791 if (vm_page_lookup(object, tpindex - 1))
1796 while (tpindex < pindex) {
1797 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_SYSTEM);
1800 for (j = 0; j < i; j++) {
1801 vm_page_free(marray[j]);
1817 * Assign requested page
1824 * Scan forwards for read-ahead pages
1826 tpindex = pindex + 1;
1827 endpindex = tpindex + rahead;
1828 if (endpindex > object->size)
1829 endpindex = object->size;
1832 while (tpindex < endpindex) {
1833 if (vm_page_lookup(object, tpindex))
1835 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_SYSTEM);
1850 * vm_prefault() provides a quick way of clustering pagefaults into a
1851 * processes address space. It is a "cousin" of pmap_object_init_pt,
1852 * except it runs at page fault time instead of mmap time.
1854 * This code used to be per-platform pmap_prefault(). It is now
1855 * machine-independent and enhanced to also pre-fault zero-fill pages
1856 * (see vm.fast_fault) as well as make them writable, which greatly
1857 * reduces the number of page faults programs incur.
1859 * Application performance when pre-faulting zero-fill pages is heavily
1860 * dependent on the application. Very tiny applications like /bin/echo
1861 * lose a little performance while applications of any appreciable size
1862 * gain performance. Prefaulting multiple pages also reduces SMP
1863 * congestion and can improve SMP performance significantly.
1865 * NOTE! prot may allow writing but this only applies to the top level
1866 * object. If we wind up mapping a page extracted from a backing
1867 * object we have to make sure it is read-only.
1869 * NOTE! The caller has already handled any COW operations on the
1870 * vm_map_entry via the normal fault code. Do NOT call this
1871 * shortcut unless the normal fault code has run on this entry.
1875 #define PAGEORDER_SIZE (PFBAK+PFFOR)
1877 static int vm_prefault_pageorder[] = {
1878 -PAGE_SIZE, PAGE_SIZE,
1879 -2 * PAGE_SIZE, 2 * PAGE_SIZE,
1880 -3 * PAGE_SIZE, 3 * PAGE_SIZE,
1881 -4 * PAGE_SIZE, 4 * PAGE_SIZE
1885 vm_prefault(pmap_t pmap, vm_offset_t addra, vm_map_entry_t entry, int prot)
1898 * We do not currently prefault mappings that use virtual page
1899 * tables. We do not prefault foreign pmaps.
1901 if (entry->maptype == VM_MAPTYPE_VPAGETABLE)
1903 lp = curthread->td_lwp;
1904 if (lp == NULL || (pmap != vmspace_pmap(lp->lwp_vmspace)))
1907 object = entry->object.vm_object;
1909 starta = addra - PFBAK * PAGE_SIZE;
1910 if (starta < entry->start)
1911 starta = entry->start;
1912 else if (starta > addra)
1916 * critical section protection is required to maintain the
1917 * page/object association, interrupts can free pages and remove
1918 * them from their objects.
1921 for (i = 0; i < PAGEORDER_SIZE; i++) {
1922 vm_object_t lobject;
1925 addr = addra + vm_prefault_pageorder[i];
1926 if (addr > addra + (PFFOR * PAGE_SIZE))
1929 if (addr < starta || addr >= entry->end)
1932 if (pmap_prefault_ok(pmap, addr) == 0)
1936 * Follow the VM object chain to obtain the page to be mapped
1939 * If we reach the terminal object without finding a page
1940 * and we determine it would be advantageous, then allocate
1941 * a zero-fill page for the base object. The base object
1942 * is guaranteed to be OBJT_DEFAULT for this case.
1944 * In order to not have to check the pager via *haspage*()
1945 * we stop if any non-default object is encountered. e.g.
1946 * a vnode or swap object would stop the loop.
1948 index = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
1953 while ((m = vm_page_lookup(lobject, pindex)) == NULL) {
1954 if (lobject->type != OBJT_DEFAULT)
1956 if (lobject->backing_object == NULL) {
1957 if (vm_fast_fault == 0)
1959 if (vm_prefault_pageorder[i] < 0 ||
1960 (prot & VM_PROT_WRITE) == 0 ||
1961 vm_page_count_min(0)) {
1964 /* note: allocate from base object */
1965 m = vm_page_alloc(object, index,
1966 VM_ALLOC_NORMAL | VM_ALLOC_ZERO);
1968 if ((m->flags & PG_ZERO) == 0) {
1969 vm_page_zero_fill(m);
1971 vm_page_flag_clear(m, PG_ZERO);
1972 mycpu->gd_cnt.v_ozfod++;
1974 mycpu->gd_cnt.v_zfod++;
1975 m->valid = VM_PAGE_BITS_ALL;
1978 /* lobject = object .. not needed */
1981 if (lobject->backing_object_offset & PAGE_MASK)
1983 pindex += lobject->backing_object_offset >> PAGE_SHIFT;
1984 lobject = lobject->backing_object;
1985 pprot &= ~VM_PROT_WRITE;
1988 * NOTE: lobject now invalid (if we did a zero-fill we didn't
1989 * bother assigning lobject = object).
1991 * Give-up if the page is not available.
1997 * Do not conditionalize on PG_RAM. If pages are present in
1998 * the VM system we assume optimal caching. If caching is
1999 * not optimal the I/O gravy train will be restarted when we
2000 * hit an unavailable page. We do not want to try to restart
2001 * the gravy train now because we really don't know how much
2002 * of the object has been cached. The cost for restarting
2003 * the gravy train should be low (since accesses will likely
2004 * be I/O bound anyway).
2006 * The object must be marked dirty if we are mapping a
2009 if (pprot & VM_PROT_WRITE)
2010 vm_object_set_writeable_dirty(m->object);
2013 * Enter the page into the pmap if appropriate. If we had
2014 * allocated the page we have to place it on a queue. If not
2015 * we just have to make sure it isn't on the cache queue
2016 * (pages on the cache queue are not allowed to be mapped).
2019 pmap_enter(pmap, addr, m, pprot, 0);
2020 vm_page_deactivate(m);
2022 } else if (((m->valid & VM_PAGE_BITS_ALL) == VM_PAGE_BITS_ALL) &&
2024 (m->flags & (PG_BUSY | PG_FICTITIOUS)) == 0) {
2026 if ((m->queue - m->pc) == PQ_CACHE) {
2027 vm_page_deactivate(m);
2030 pmap_enter(pmap, addr, m, pprot, 0);