/* $OpenBSD: vm_object.c,v 1.4 1996/04/19 16:10:51 niklas Exp $ */ /* $NetBSD: vm_object.c,v 1.34 1996/02/28 22:35:35 gwr Exp $ */ /* * Copyright (c) 1991, 1993 * The Regents of the University of California. All rights reserved. * * This code is derived from software contributed to Berkeley by * The Mach Operating System project at Carnegie-Mellon University. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * @(#)vm_object.c 8.5 (Berkeley) 3/22/94 * * * Copyright (c) 1987, 1990 Carnegie-Mellon University. * All rights reserved. * * Authors: Avadis Tevanian, Jr., Michael Wayne Young * * Permission to use, copy, modify and distribute this software and * its documentation is hereby granted, provided that both the copyright * notice and this permission notice appear in all copies of the * software, derivative works or modified versions, and any portions * thereof, and that both notices appear in supporting documentation. * * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. * * Carnegie Mellon requests users of this software to return to * * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU * School of Computer Science * Carnegie Mellon University * Pittsburgh PA 15213-3890 * * any improvements or extensions that they make and grant Carnegie the * rights to redistribute these changes. */ /* * Virtual memory object module. */ #include #include #include #include #include /* * Virtual memory objects maintain the actual data * associated with allocated virtual memory. A given * page of memory exists within exactly one object. * * An object is only deallocated when all "references" * are given up. Only one "reference" to a given * region of an object should be writeable. * * Associated with each object is a list of all resident * memory pages belonging to that object; this list is * maintained by the "vm_page" module, and locked by the object's * lock. * * Each object also records a "pager" routine which is * used to retrieve (and store) pages to the proper backing * storage. In addition, objects may be backed by other * objects from which they were virtual-copied. * * The only items within the object structure which are * modified after time of creation are: * reference count locked by object's lock * pager routine locked by object's lock * */ struct vm_object kernel_object_store; struct vm_object kmem_object_store; #define VM_OBJECT_HASH_COUNT 157 int vm_cache_max = 100; /* can patch if necessary */ struct vm_object_hash_head vm_object_hashtable[VM_OBJECT_HASH_COUNT]; long object_collapses = 0; long object_bypasses = 0; static void _vm_object_allocate __P((vm_size_t, vm_object_t)); /* * vm_object_init: * * Initialize the VM objects module. */ void vm_object_init(size) vm_size_t size; { register int i; TAILQ_INIT(&vm_object_cached_list); TAILQ_INIT(&vm_object_list); vm_object_count = 0; simple_lock_init(&vm_cache_lock); simple_lock_init(&vm_object_list_lock); for (i = 0; i < VM_OBJECT_HASH_COUNT; i++) TAILQ_INIT(&vm_object_hashtable[i]); kernel_object = &kernel_object_store; _vm_object_allocate(size, kernel_object); kmem_object = &kmem_object_store; _vm_object_allocate(VM_KMEM_SIZE + VM_MBUF_SIZE, kmem_object); } /* * vm_object_allocate: * * Returns a new object with the given size. */ vm_object_t vm_object_allocate(size) vm_size_t size; { register vm_object_t result; result = (vm_object_t) malloc((u_long)sizeof *result, M_VMOBJ, M_WAITOK); _vm_object_allocate(size, result); return(result); } static void _vm_object_allocate(size, object) vm_size_t size; register vm_object_t object; { TAILQ_INIT(&object->memq); vm_object_lock_init(object); object->ref_count = 1; object->resident_page_count = 0; object->size = size; object->flags = OBJ_INTERNAL; /* vm_allocate_with_pager will reset */ object->paging_in_progress = 0; object->copy = NULL; /* * Object starts out read-write, with no pager. */ object->pager = NULL; object->paging_offset = 0; object->shadow = NULL; object->shadow_offset = (vm_offset_t) 0; simple_lock(&vm_object_list_lock); TAILQ_INSERT_TAIL(&vm_object_list, object, object_list); vm_object_count++; cnt.v_nzfod += atop(size); simple_unlock(&vm_object_list_lock); } /* * vm_object_reference: * * Gets another reference to the given object. */ void vm_object_reference(object) register vm_object_t object; { if (object == NULL) return; vm_object_lock(object); object->ref_count++; vm_object_unlock(object); } /* * vm_object_deallocate: * * Release a reference to the specified object, * gained either through a vm_object_allocate * or a vm_object_reference call. When all references * are gone, storage associated with this object * may be relinquished. * * No object may be locked. */ void vm_object_deallocate(object) register vm_object_t object; { vm_object_t temp; while (object != NULL) { /* * The cache holds a reference (uncounted) to * the object; we must lock it before removing * the object. */ vm_object_cache_lock(); /* * Lose the reference */ vm_object_lock(object); if (--(object->ref_count) != 0) { /* * If there are still references, then * we are done. */ vm_object_unlock(object); vm_object_cache_unlock(); return; } /* * See if this object can persist. If so, enter * it in the cache, then deactivate all of its * pages. */ if (object->flags & OBJ_CANPERSIST) { TAILQ_INSERT_TAIL(&vm_object_cached_list, object, cached_list); vm_object_cached++; vm_object_cache_unlock(); vm_object_deactivate_pages(object); vm_object_unlock(object); vm_object_cache_trim(); return; } /* * Make sure no one can look us up now. */ vm_object_remove(object->pager); vm_object_cache_unlock(); temp = object->shadow; vm_object_terminate(object); /* unlocks and deallocates object */ object = temp; } } /* * vm_object_terminate actually destroys the specified object, freeing * up all previously used resources. * * The object must be locked. */ void vm_object_terminate(object) register vm_object_t object; { register vm_page_t p; vm_object_t shadow_object; /* * Detach the object from its shadow if we are the shadow's * copy. */ if ((shadow_object = object->shadow) != NULL) { vm_object_lock(shadow_object); if (shadow_object->copy == object) shadow_object->copy = NULL; #if 0 else if (shadow_object->copy != NULL) panic("vm_object_terminate: copy/shadow inconsistency"); #endif vm_object_unlock(shadow_object); } /* * Wait until the pageout daemon is through with the object. */ while (object->paging_in_progress) { vm_object_sleep(object, object, FALSE); vm_object_lock(object); } /* * If not an internal object clean all the pages, removing them * from paging queues as we go. * * XXX need to do something in the event of a cleaning error. */ if ((object->flags & OBJ_INTERNAL) == 0) { (void) vm_object_page_clean(object, 0, 0, TRUE, TRUE); vm_object_unlock(object); } /* * Now free the pages. * For internal objects, this also removes them from paging queues. */ while ((p = object->memq.tqh_first) != NULL) { VM_PAGE_CHECK(p); vm_page_lock_queues(); vm_page_free(p); cnt.v_pfree++; vm_page_unlock_queues(); } if ((object->flags & OBJ_INTERNAL) != 0) vm_object_unlock(object); /* * Let the pager know object is dead. */ if (object->pager != NULL) vm_pager_deallocate(object->pager); simple_lock(&vm_object_list_lock); TAILQ_REMOVE(&vm_object_list, object, object_list); vm_object_count--; simple_unlock(&vm_object_list_lock); /* * Free the space for the object. */ free((caddr_t)object, M_VMOBJ); } /* * vm_object_page_clean * * Clean all dirty pages in the specified range of object. * If syncio is TRUE, page cleaning is done synchronously. * If de_queue is TRUE, pages are removed from any paging queue * they were on, otherwise they are left on whatever queue they * were on before the cleaning operation began. * * Odd semantics: if start == end, we clean everything. * * The object must be locked. * * Returns TRUE if all was well, FALSE if there was a pager error * somewhere. We attempt to clean (and dequeue) all pages regardless * of where an error occurs. */ boolean_t vm_object_page_clean(object, start, end, syncio, de_queue) register vm_object_t object; register vm_offset_t start; register vm_offset_t end; boolean_t syncio; boolean_t de_queue; { register vm_page_t p; int onqueue = 0; boolean_t noerror = TRUE; if (object == NULL) return (TRUE); /* * If it is an internal object and there is no pager, attempt to * allocate one. Note that vm_object_collapse may relocate one * from a collapsed object so we must recheck afterward. */ if ((object->flags & OBJ_INTERNAL) && object->pager == NULL) { vm_object_collapse(object); if (object->pager == NULL) { vm_pager_t pager; vm_object_unlock(object); pager = vm_pager_allocate(PG_DFLT, (caddr_t)0, object->size, VM_PROT_ALL, (vm_offset_t)0); if (pager) vm_object_setpager(object, pager, 0, FALSE); vm_object_lock(object); } } if (object->pager == NULL) return (FALSE); again: /* * Wait until the pageout daemon is through with the object. */ while (object->paging_in_progress) { vm_object_sleep(object, object, FALSE); vm_object_lock(object); } /* * Loop through the object page list cleaning as necessary. */ for (p = object->memq.tqh_first; p != NULL; p = p->listq.tqe_next) { if ((start == end || (p->offset >= start && p->offset < end)) && !(p->flags & PG_FICTITIOUS)) { if ((p->flags & PG_CLEAN) && pmap_is_modified(VM_PAGE_TO_PHYS(p))) p->flags &= ~PG_CLEAN; /* * Remove the page from any paging queue. * This needs to be done if either we have been * explicitly asked to do so or it is about to * be cleaned (see comment below). */ if (de_queue || !(p->flags & PG_CLEAN)) { vm_page_lock_queues(); if (p->flags & PG_ACTIVE) { TAILQ_REMOVE(&vm_page_queue_active, p, pageq); p->flags &= ~PG_ACTIVE; cnt.v_active_count--; onqueue = 1; } else if (p->flags & PG_INACTIVE) { TAILQ_REMOVE(&vm_page_queue_inactive, p, pageq); p->flags &= ~PG_INACTIVE; cnt.v_inactive_count--; onqueue = -1; } else onqueue = 0; vm_page_unlock_queues(); } /* * To ensure the state of the page doesn't change * during the clean operation we do two things. * First we set the busy bit and write-protect all * mappings to ensure that write accesses to the * page block (in vm_fault). Second, we remove * the page from any paging queue to foil the * pageout daemon (vm_pageout_scan). */ pmap_page_protect(VM_PAGE_TO_PHYS(p), VM_PROT_READ); if (!(p->flags & PG_CLEAN)) { p->flags |= PG_BUSY; object->paging_in_progress++; vm_object_unlock(object); /* * XXX if put fails we mark the page as * clean to avoid an infinite loop. * Will loose changes to the page. */ if (vm_pager_put(object->pager, p, syncio)) { printf("%s: pager_put error\n", "vm_object_page_clean"); p->flags |= PG_CLEAN; noerror = FALSE; } vm_object_lock(object); object->paging_in_progress--; if (!de_queue && onqueue) { vm_page_lock_queues(); if (onqueue > 0) vm_page_activate(p); else vm_page_deactivate(p); vm_page_unlock_queues(); } p->flags &= ~PG_BUSY; PAGE_WAKEUP(p); goto again; } } } return (noerror); } /* * vm_object_deactivate_pages * * Deactivate all pages in the specified object. (Keep its pages * in memory even though it is no longer referenced.) * * The object must be locked. */ void vm_object_deactivate_pages(object) register vm_object_t object; { register vm_page_t p, next; for (p = object->memq.tqh_first; p != NULL; p = next) { next = p->listq.tqe_next; vm_page_lock_queues(); if (p->flags & PG_ACTIVE) vm_page_deactivate(p); vm_page_unlock_queues(); } } /* * Trim the object cache to size. */ void vm_object_cache_trim() { register vm_object_t object; vm_object_cache_lock(); while (vm_object_cached > vm_cache_max) { object = vm_object_cached_list.tqh_first; vm_object_cache_unlock(); if (object != vm_object_lookup(object->pager)) panic("vm_object_deactivate: I'm sooo confused."); pager_cache(object, FALSE); vm_object_cache_lock(); } vm_object_cache_unlock(); } /* * vm_object_pmap_copy: * * Makes all physical pages in the specified * object range copy-on-write. No writeable * references to these pages should remain. * * The object must *not* be locked. */ void vm_object_pmap_copy(object, start, end) register vm_object_t object; register vm_offset_t start; register vm_offset_t end; { register vm_page_t p; if (object == NULL) return; vm_object_lock(object); for (p = object->memq.tqh_first; p != NULL; p = p->listq.tqe_next) { if ((start <= p->offset) && (p->offset < end)) { pmap_page_protect(VM_PAGE_TO_PHYS(p), VM_PROT_READ); p->flags |= PG_COPYONWRITE; } } vm_object_unlock(object); } /* * vm_object_pmap_remove: * * Removes all physical pages in the specified * object range from all physical maps. * * The object must *not* be locked. */ void vm_object_pmap_remove(object, start, end) register vm_object_t object; register vm_offset_t start; register vm_offset_t end; { register vm_page_t p; if (object == NULL) return; vm_object_lock(object); for (p = object->memq.tqh_first; p != NULL; p = p->listq.tqe_next) if ((start <= p->offset) && (p->offset < end)) pmap_page_protect(VM_PAGE_TO_PHYS(p), VM_PROT_NONE); vm_object_unlock(object); } /* * vm_object_copy: * * Create a new object which is a copy of an existing * object, and mark all of the pages in the existing * object 'copy-on-write'. The new object has one reference. * Returns the new object. * * May defer the copy until later if the object is not backed * up by a non-default pager. */ void vm_object_copy(src_object, src_offset, size, dst_object, dst_offset, src_needs_copy) register vm_object_t src_object; vm_offset_t src_offset; vm_size_t size; vm_object_t *dst_object; /* OUT */ vm_offset_t *dst_offset; /* OUT */ boolean_t *src_needs_copy; /* OUT */ { register vm_object_t new_copy; register vm_object_t old_copy; vm_offset_t new_start, new_end; register vm_page_t p; if (src_object == NULL) { /* * Nothing to copy */ *dst_object = NULL; *dst_offset = 0; *src_needs_copy = FALSE; return; } /* * If the object's pager is null_pager or the * default pager, we don't have to make a copy * of it. Instead, we set the needs copy flag and * make a shadow later. */ vm_object_lock(src_object); if (src_object->pager == NULL || (src_object->flags & OBJ_INTERNAL)) { /* * Make another reference to the object */ src_object->ref_count++; /* * Mark all of the pages copy-on-write. */ for (p = src_object->memq.tqh_first; p; p = p->listq.tqe_next) if (src_offset <= p->offset && p->offset < src_offset + size) p->flags |= PG_COPYONWRITE; vm_object_unlock(src_object); *dst_object = src_object; *dst_offset = src_offset; /* * Must make a shadow when write is desired */ *src_needs_copy = TRUE; return; } /* * Try to collapse the object before copying it. */ vm_object_collapse(src_object); /* * If the object has a pager, the pager wants to * see all of the changes. We need a copy-object * for the changed pages. * * If there is a copy-object, and it is empty, * no changes have been made to the object since the * copy-object was made. We can use the same copy- * object. */ Retry1: old_copy = src_object->copy; if (old_copy != NULL) { /* * Try to get the locks (out of order) */ if (!vm_object_lock_try(old_copy)) { vm_object_unlock(src_object); /* should spin a bit here... */ vm_object_lock(src_object); goto Retry1; } if (old_copy->resident_page_count == 0 && old_copy->pager == NULL) { /* * Return another reference to * the existing copy-object. */ old_copy->ref_count++; vm_object_unlock(old_copy); vm_object_unlock(src_object); *dst_object = old_copy; *dst_offset = src_offset; *src_needs_copy = FALSE; return; } vm_object_unlock(old_copy); } vm_object_unlock(src_object); /* * If the object has a pager, the pager wants * to see all of the changes. We must make * a copy-object and put the changed pages there. * * The copy-object is always made large enough to * completely shadow the original object, since * it may have several users who want to shadow * the original object at different points. */ new_copy = vm_object_allocate(src_object->size); Retry2: vm_object_lock(src_object); /* * Copy object may have changed while we were unlocked */ old_copy = src_object->copy; if (old_copy != NULL) { /* * Try to get the locks (out of order) */ if (!vm_object_lock_try(old_copy)) { vm_object_unlock(src_object); goto Retry2; } /* * Consistency check */ if (old_copy->shadow != src_object || old_copy->shadow_offset != (vm_offset_t) 0) panic("vm_object_copy: copy/shadow inconsistency"); /* * Make the old copy-object shadow the new one. * It will receive no more pages from the original * object. */ src_object->ref_count--; /* remove ref. from old_copy */ old_copy->shadow = new_copy; new_copy->ref_count++; /* locking not needed - we have the only pointer */ vm_object_unlock(old_copy); /* done with old_copy */ } new_start = (vm_offset_t) 0; /* always shadow original at 0 */ new_end = (vm_offset_t) new_copy->size; /* for the whole object */ /* * Point the new copy at the existing object. */ new_copy->shadow = src_object; new_copy->shadow_offset = new_start; src_object->ref_count++; src_object->copy = new_copy; /* * Mark all the affected pages of the existing object * copy-on-write. */ for (p = src_object->memq.tqh_first; p != NULL; p = p->listq.tqe_next) if ((new_start <= p->offset) && (p->offset < new_end)) p->flags |= PG_COPYONWRITE; vm_object_unlock(src_object); *dst_object = new_copy; *dst_offset = src_offset - new_start; *src_needs_copy = FALSE; } /* * vm_object_shadow: * * Create a new object which is backed by the * specified existing object range. The source * object reference is deallocated. * * The new object and offset into that object * are returned in the source parameters. */ void vm_object_shadow(object, offset, length) vm_object_t *object; /* IN/OUT */ vm_offset_t *offset; /* IN/OUT */ vm_size_t length; { register vm_object_t source; register vm_object_t result; source = *object; /* * Allocate a new object with the given length */ if ((result = vm_object_allocate(length)) == NULL) panic("vm_object_shadow: no object for shadowing"); /* * The new object shadows the source object, adding * a reference to it. Our caller changes his reference * to point to the new object, removing a reference to * the source object. Net result: no change of reference * count. */ result->shadow = source; /* * Store the offset into the source object, * and fix up the offset into the new object. */ result->shadow_offset = *offset; /* * Return the new things */ *offset = 0; *object = result; } /* * Set the specified object's pager to the specified pager. */ void vm_object_setpager(object, pager, paging_offset, read_only) vm_object_t object; vm_pager_t pager; vm_offset_t paging_offset; boolean_t read_only; { #ifdef lint read_only++; /* No longer used */ #endif vm_object_lock(object); /* XXX ? */ object->pager = pager; object->paging_offset = paging_offset; vm_object_unlock(object); /* XXX ? */ } /* * vm_object_hash hashes the pager/id pair. */ #define vm_object_hash(pager) \ (((unsigned long)pager)%VM_OBJECT_HASH_COUNT) /* * vm_object_lookup looks in the object cache for an object with the * specified pager and paging id. */ vm_object_t vm_object_lookup(pager) vm_pager_t pager; { register vm_object_hash_entry_t entry; vm_object_t object; vm_object_cache_lock(); for (entry = vm_object_hashtable[vm_object_hash(pager)].tqh_first; entry != NULL; entry = entry->hash_links.tqe_next) { object = entry->object; if (object->pager == pager) { vm_object_lock(object); if (object->ref_count == 0) { TAILQ_REMOVE(&vm_object_cached_list, object, cached_list); vm_object_cached--; } object->ref_count++; vm_object_unlock(object); vm_object_cache_unlock(); return(object); } } vm_object_cache_unlock(); return(NULL); } /* * vm_object_enter enters the specified object/pager/id into * the hash table. */ void vm_object_enter(object, pager) vm_object_t object; vm_pager_t pager; { struct vm_object_hash_head *bucket; register vm_object_hash_entry_t entry; /* * We don't cache null objects, and we can't cache * objects with the null pager. */ if (object == NULL) return; if (pager == NULL) return; bucket = &vm_object_hashtable[vm_object_hash(pager)]; entry = (vm_object_hash_entry_t) malloc((u_long)sizeof *entry, M_VMOBJHASH, M_WAITOK); entry->object = object; object->flags |= OBJ_CANPERSIST; vm_object_cache_lock(); TAILQ_INSERT_TAIL(bucket, entry, hash_links); vm_object_cache_unlock(); } /* * vm_object_remove: * * Remove the pager from the hash table. * Note: This assumes that the object cache * is locked. XXX this should be fixed * by reorganizing vm_object_deallocate. */ void vm_object_remove(pager) register vm_pager_t pager; { struct vm_object_hash_head *bucket; register vm_object_hash_entry_t entry; register vm_object_t object; bucket = &vm_object_hashtable[vm_object_hash(pager)]; for (entry = bucket->tqh_first; entry != NULL; entry = entry->hash_links.tqe_next) { object = entry->object; if (object->pager == pager) { TAILQ_REMOVE(bucket, entry, hash_links); free((caddr_t)entry, M_VMOBJHASH); break; } } } /* * vm_object_cache_clear removes all objects from the cache. * */ void vm_object_cache_clear() { register vm_object_t object; /* * Remove each object in the cache by scanning down the * list of cached objects. */ vm_object_cache_lock(); while ((object = vm_object_cached_list.tqh_first) != NULL) { vm_object_cache_unlock(); /* * Note: it is important that we use vm_object_lookup * to gain a reference, and not vm_object_reference, because * the logic for removing an object from the cache lies in * lookup. */ if (object != vm_object_lookup(object->pager)) panic("vm_object_cache_clear: I'm sooo confused."); pager_cache(object, FALSE); vm_object_cache_lock(); } vm_object_cache_unlock(); } boolean_t vm_object_collapse_allowed = TRUE; /* * vm_object_collapse: * * Collapse an object with the object backing it. * Pages in the backing object are moved into the * parent, and the backing object is deallocated. * * Requires that the object be locked and the page * queues be unlocked. * */ void vm_object_collapse(object) register vm_object_t object; { register vm_object_t backing_object; register vm_offset_t backing_offset; register vm_size_t size; register vm_offset_t new_offset; register vm_page_t p, pp; if (!vm_object_collapse_allowed) return; while (TRUE) { /* * Verify that the conditions are right for collapse: * * The object exists and no pages in it are currently * being paged out (or have ever been paged out). */ if (object == NULL || object->paging_in_progress != 0 || object->pager != NULL) return; /* * There is a backing object, and */ if ((backing_object = object->shadow) == NULL) return; vm_object_lock(backing_object); /* * ... * The backing object is not read_only, * and no pages in the backing object are * currently being paged out. * The backing object is internal. */ if ((backing_object->flags & OBJ_INTERNAL) == 0 || backing_object->paging_in_progress != 0) { vm_object_unlock(backing_object); return; } /* * The backing object can't be a copy-object: * the shadow_offset for the copy-object must stay * as 0. Furthermore (for the 'we have all the * pages' case), if we bypass backing_object and * just shadow the next object in the chain, old * pages from that object would then have to be copied * BOTH into the (former) backing_object and into the * parent object. */ if (backing_object->shadow != NULL && backing_object->shadow->copy != NULL) { vm_object_unlock(backing_object); return; } /* * We know that we can either collapse the backing * object (if the parent is the only reference to * it) or (perhaps) remove the parent's reference * to it. */ backing_offset = object->shadow_offset; size = object->size; /* * If there is exactly one reference to the backing * object, we can collapse it into the parent. */ if (backing_object->ref_count == 1) { /* * We can collapse the backing object. * * Move all in-memory pages from backing_object * to the parent. Pages that have been paged out * will be overwritten by any of the parent's * pages that shadow them. */ while ((p = backing_object->memq.tqh_first) != NULL) { new_offset = (p->offset - backing_offset); /* * If the parent has a page here, or if * this page falls outside the parent, * dispose of it. * * Otherwise, move it as planned. */ if (p->offset < backing_offset || new_offset >= size) { vm_page_lock_queues(); vm_page_free(p); vm_page_unlock_queues(); } else { pp = vm_page_lookup(object, new_offset); if (pp != NULL && !(pp->flags & PG_FAKE)) { vm_page_lock_queues(); vm_page_free(p); vm_page_unlock_queues(); } else { if (pp) { /* may be someone waiting for it */ PAGE_WAKEUP(pp); vm_page_lock_queues(); vm_page_free(pp); vm_page_unlock_queues(); } vm_page_rename(p, object, new_offset); } } } /* * Move the pager from backing_object to object. * * XXX We're only using part of the paging space * for keeps now... we ought to discard the * unused portion. */ if (backing_object->pager) { object->pager = backing_object->pager; object->paging_offset = backing_offset + backing_object->paging_offset; backing_object->pager = NULL; } /* * Object now shadows whatever backing_object did. * Note that the reference to backing_object->shadow * moves from within backing_object to within object. */ object->shadow = backing_object->shadow; object->shadow_offset += backing_object->shadow_offset; if (object->shadow != NULL && object->shadow->copy != NULL) { panic("vm_object_collapse: we collapsed a copy-object!"); } /* * Discard backing_object. * * Since the backing object has no pages, no * pager left, and no object references within it, * all that is necessary is to dispose of it. */ vm_object_unlock(backing_object); simple_lock(&vm_object_list_lock); TAILQ_REMOVE(&vm_object_list, backing_object, object_list); vm_object_count--; simple_unlock(&vm_object_list_lock); free((caddr_t)backing_object, M_VMOBJ); object_collapses++; } else { /* * If all of the pages in the backing object are * shadowed by the parent object, the parent * object no longer has to shadow the backing * object; it can shadow the next one in the * chain. * * The backing object must not be paged out - we'd * have to check all of the paged-out pages, as * well. */ if (backing_object->pager != NULL) { vm_object_unlock(backing_object); return; } /* * Should have a check for a 'small' number * of pages here. */ for (p = backing_object->memq.tqh_first; p != NULL; p = p->listq.tqe_next) { new_offset = (p->offset - backing_offset); /* * If the parent has a page here, or if * this page falls outside the parent, * keep going. * * Otherwise, the backing_object must be * left in the chain. */ if (p->offset >= backing_offset && new_offset < size && ((pp = vm_page_lookup(object, new_offset)) == NULL || (pp->flags & PG_FAKE))) { /* * Page still needed. * Can't go any further. */ vm_object_unlock(backing_object); return; } } /* * Make the parent shadow the next object * in the chain. Deallocating backing_object * will not remove it, since its reference * count is at least 2. */ object->shadow = backing_object->shadow; vm_object_reference(object->shadow); object->shadow_offset += backing_object->shadow_offset; /* * Backing object might have had a copy pointer * to us. If it did, clear it. */ if (backing_object->copy == object) { backing_object->copy = NULL; } /* Drop the reference count on backing_object. * Since its ref_count was at least 2, it * will not vanish; so we don't need to call * vm_object_deallocate. */ backing_object->ref_count--; vm_object_unlock(backing_object); object_bypasses ++; } /* * Try again with this object's new backing object. */ } } /* * vm_object_page_remove: [internal] * * Removes all physical pages in the specified * object range from the object's list of pages. * * The object must be locked. */ void vm_object_page_remove(object, start, end) register vm_object_t object; register vm_offset_t start; register vm_offset_t end; { register vm_page_t p, next; if (object == NULL) return; for (p = object->memq.tqh_first; p != NULL; p = next) { next = p->listq.tqe_next; if ((start <= p->offset) && (p->offset < end)) { pmap_page_protect(VM_PAGE_TO_PHYS(p), VM_PROT_NONE); vm_page_lock_queues(); vm_page_free(p); vm_page_unlock_queues(); } } } /* * Routine: vm_object_coalesce * Function: Coalesces two objects backing up adjoining * regions of memory into a single object. * * returns TRUE if objects were combined. * * NOTE: Only works at the moment if the second object is NULL - * if it's not, which object do we lock first? * * Parameters: * prev_object First object to coalesce * prev_offset Offset into prev_object * next_object Second object into coalesce * next_offset Offset into next_object * * prev_size Size of reference to prev_object * next_size Size of reference to next_object * * Conditions: * The object must *not* be locked. */ boolean_t vm_object_coalesce(prev_object, next_object, prev_offset, next_offset, prev_size, next_size) register vm_object_t prev_object; vm_object_t next_object; vm_offset_t prev_offset, next_offset; vm_size_t prev_size, next_size; { vm_size_t newsize; #ifdef lint next_offset++; #endif if (next_object != NULL) { return(FALSE); } if (prev_object == NULL) { return(TRUE); } vm_object_lock(prev_object); /* * Try to collapse the object first */ vm_object_collapse(prev_object); /* * Can't coalesce if: * . more than one reference * . paged out * . shadows another object * . has a copy elsewhere * (any of which mean that the pages not mapped to * prev_entry may be in use anyway) */ if (prev_object->ref_count > 1 || prev_object->pager != NULL || prev_object->shadow != NULL || prev_object->copy != NULL) { vm_object_unlock(prev_object); return(FALSE); } /* * Remove any pages that may still be in the object from * a previous deallocation. */ vm_object_page_remove(prev_object, prev_offset + prev_size, prev_offset + prev_size + next_size); /* * Extend the object if necessary. */ newsize = prev_offset + prev_size + next_size; if (newsize > prev_object->size) prev_object->size = newsize; vm_object_unlock(prev_object); return(TRUE); } /* * vm_object_print: [ debug ] */ void vm_object_print(object, full) vm_object_t object; boolean_t full; { _vm_object_print(object, full, printf); } void _vm_object_print(object, full, pr) vm_object_t object; boolean_t full; void (*pr) __P((const char *, ...)); { register vm_page_t p; extern indent; register int count; if (object == NULL) return; iprintf(pr, "Object 0x%lx: size=0x%lx, res=%d, ref=%d, ", (long) object, (long) object->size, object->resident_page_count, object->ref_count); (*pr)("pager=0x%lx+0x%lx, shadow=(0x%lx)+0x%lx\n", (long) object->pager, (long) object->paging_offset, (long) object->shadow, (long) object->shadow_offset); (*pr)("cache: next=0x%lx, prev=0x%lx\n", (long)object->cached_list.tqe_next, (long)object->cached_list.tqe_prev); if (!full) return; indent += 2; count = 0; for (p = object->memq.tqh_first; p != NULL; p = p->listq.tqe_next) { if (count == 0) iprintf(pr, "memory:="); else if (count == 6) { (*pr)("\n"); iprintf(pr, " ..."); count = 0; } else (*pr)(","); count++; (*pr)("(off=0x%x,page=0x%x)", p->offset, VM_PAGE_TO_PHYS(p)); } if (count != 0) (*pr)("\n"); indent -= 2; }