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This commit was manufactured by cvs2svn to create tag 'FreeBSD-release/1.0'.
[unix-history] / sys / vm / vm_object.c
/*
* Copyright (c) 1991 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.
*
* from: @(#)vm_object.c 7.4 (Berkeley) 5/7/91
* $Id$
*/
/*
* 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 "ddb.h"
#include "param.h"
#include "malloc.h"
#include "vm.h"
#include "vm_page.h"
/*
* 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 */
queue_head_t vm_object_hashtable[VM_OBJECT_HASH_COUNT];
long object_collapses = 0;
long object_bypasses = 0;
/*
* vm_object_init:
*
* Initialize the VM objects module.
*/
void vm_object_init()
{
register int i;
queue_init(&vm_object_cached_list);
queue_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++)
queue_init(&vm_object_hashtable[i]);
kernel_object = &kernel_object_store;
_vm_object_allocate(VM_MAX_KERNEL_ADDRESS - VM_MIN_KERNEL_ADDRESS,
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);
}
_vm_object_allocate(size, object)
vm_size_t size;
register vm_object_t object;
{
queue_init(&object->memq);
vm_object_lock_init(object);
object->ref_count = 1;
object->resident_page_count = 0;
object->size = size;
object->can_persist = FALSE;
object->paging_in_progress = 0;
object->copy = NULL;
/*
* Object starts out read-write, with no pager.
*/
object->pager = NULL;
object->pager_ready = FALSE;
object->internal = TRUE; /* vm_allocate_with_pager will reset */
object->paging_offset = 0;
object->shadow = NULL;
object->shadow_offset = (vm_offset_t) 0;
simple_lock(&vm_object_list_lock);
queue_enter(&vm_object_list, object, vm_object_t, object_list);
vm_object_count++;
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->can_persist) {
#ifdef DIAGNOSTIC
register vm_page_t p;
/*
* Check for dirty pages in object
* Print warning as this may signify kernel bugs
* pk@cs.few.eur.nl - 4/15/93
*/
p = (vm_page_t) queue_first(&object->memq);
while (!queue_end(&object->memq, (queue_entry_t) p)) {
VM_PAGE_CHECK(p);
if (pmap_is_modified(VM_PAGE_TO_PHYS(p)) ||
!p->clean) {
printf("vm_object_dealloc: persistent object %x isn't clean\n", object);
goto cant_persist;
}
p = (vm_page_t) queue_next(&p->listq);
}
#endif /* DIAGNOSTIC */
queue_enter(&vm_object_cached_list, object,
vm_object_t, cached_list);
vm_object_cached++;
vm_object_cache_unlock();
vm_object_deactivate_pages(object);
vm_object_unlock(object);
vm_object_cache_trim();
return;
}
cant_persist:;
/*
* 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 != 0) {
vm_object_sleep(object, object, FALSE);
vm_object_lock(object);
}
/*
* While the paging system is locked,
* pull the object's pages off the active
* and inactive queues. This keeps the
* pageout daemon from playing with them
* during vm_pager_deallocate.
*
* We can't free the pages yet, because the
* object's pager may have to write them out
* before deallocating the paging space.
*/
p = (vm_page_t) queue_first(&object->memq);
while (!queue_end(&object->memq, (queue_entry_t) p)) {
VM_PAGE_CHECK(p);
vm_page_lock_queues();
if (p->active) {
queue_remove(&vm_page_queue_active, p, vm_page_t,
pageq);
p->active = FALSE;
vm_page_active_count--;
}
if (p->inactive) {
queue_remove(&vm_page_queue_inactive, p, vm_page_t,
pageq);
p->inactive = FALSE;
vm_page_inactive_count--;
}
vm_page_unlock_queues();
p = (vm_page_t) queue_next(&p->listq);
}
vm_object_unlock(object);
if (object->paging_in_progress != 0)
panic("vm_object_deallocate: pageout in progress");
/*
* Clean and free the pages, as appropriate.
* All references to the object are gone,
* so we don't need to lock it.
*/
if (!object->internal) {
vm_object_lock(object);
vm_object_page_clean(object, 0, 0);
vm_object_unlock(object);
}
while (!queue_empty(&object->memq)) {
p = (vm_page_t) queue_first(&object->memq);
VM_PAGE_CHECK(p);
vm_page_lock_queues();
vm_page_free(p);
vm_page_unlock_queues();
}
/*
* Let the pager know object is dead.
*/
if (object->pager != NULL)
vm_pager_deallocate(object->pager);
simple_lock(&vm_object_list_lock);
queue_remove(&vm_object_list, object, vm_object_t, 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.
* Leaves page on whatever queue it is currently on.
*
* Odd semantics: if start == end, we clean everything.
*
* The object must be locked.
*/
vm_object_page_clean(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->pager == NULL)
return;
again:
p = (vm_page_t) queue_first(&object->memq);
while (!queue_end(&object->memq, (queue_entry_t) p)) {
if (start == end ||
p->offset >= start && p->offset < end) {
if (p->clean && pmap_is_modified(VM_PAGE_TO_PHYS(p)))
p->clean = FALSE;
pmap_page_protect(VM_PAGE_TO_PHYS(p), VM_PROT_NONE);
if (!p->clean) {
p->busy = TRUE;
object->paging_in_progress++;
vm_object_unlock(object);
(void) vm_pager_put(object->pager, p, TRUE);
vm_object_lock(object);
object->paging_in_progress--;
p->busy = FALSE;
PAGE_WAKEUP(p);
goto again;
}
}
p = (vm_page_t) queue_next(&p->listq);
}
}
/*
* 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.
*/
vm_object_deactivate_pages(object)
register vm_object_t object;
{
register vm_page_t p, next;
p = (vm_page_t) queue_first(&object->memq);
while (!queue_end(&object->memq, (queue_entry_t) p)) {
next = (vm_page_t) queue_next(&p->listq);
vm_page_lock_queues();
if (!p->busy)
vm_page_deactivate(p); /* optimisation from mach 3.0 -
* andrew@werple.apana.org.au,
* Feb '93
*/
vm_page_unlock_queues();
p = next;
}
}
/*
* Trim the object cache to size.
*/
vm_object_cache_trim()
{
register vm_object_t object;
vm_object_cache_lock();
while (vm_object_cached > vm_cache_max) {
object = (vm_object_t) queue_first(&vm_object_cached_list);
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_shutdown()
*
* Shut down the object system. Unfortunately, while we
* may be trying to do this, init is happily waiting for
* processes to exit, and therefore will be causing some objects
* to be deallocated. To handle this, we gain a fake reference
* to all objects we release paging areas for. This will prevent
* a duplicate deallocation. This routine is probably full of
* race conditions!
*/
void vm_object_shutdown()
{
register vm_object_t object;
/*
* Clean up the object cache *before* we screw up the reference
* counts on all of the objects.
*/
vm_object_cache_clear();
printf("free paging spaces: ");
/*
* First we gain a reference to each object so that
* no one else will deallocate them.
*/
simple_lock(&vm_object_list_lock);
object = (vm_object_t) queue_first(&vm_object_list);
while (!queue_end(&vm_object_list, (queue_entry_t) object)) {
vm_object_reference(object);
object = (vm_object_t) queue_next(&object->object_list);
}
simple_unlock(&vm_object_list_lock);
/*
* Now we deallocate all the paging areas. We don't need
* to lock anything because we've reduced to a single
* processor while shutting down. This also assumes that
* no new objects are being created.
*/
object = (vm_object_t) queue_first(&vm_object_list);
while (!queue_end(&vm_object_list, (queue_entry_t) object)) {
if (object->pager != NULL)
vm_pager_deallocate(object->pager);
object = (vm_object_t) queue_next(&object->object_list);
printf(".");
}
printf("done.\n");
}
/*
* 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);
p = (vm_page_t) queue_first(&object->memq);
while (!queue_end(&object->memq, (queue_entry_t) p)) {
if ((start <= p->offset) && (p->offset < end)) {
pmap_page_protect(VM_PAGE_TO_PHYS(p), VM_PROT_READ);
p->copy_on_write = TRUE;
}
p = (vm_page_t) queue_next(&p->listq);
}
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);
p = (vm_page_t) queue_first(&object->memq);
while (!queue_end(&object->memq, (queue_entry_t) p)) {
if ((start <= p->offset) && (p->offset < end))
pmap_page_protect(VM_PAGE_TO_PHYS(p), VM_PROT_NONE);
p = (vm_page_t) queue_next(&p->listq);
}
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->internal) {
/*
* Make another reference to the object
*/
src_object->ref_count++;
/*
* Mark all of the pages copy-on-write.
*/
for (p = (vm_page_t) queue_first(&src_object->memq);
!queue_end(&src_object->memq, (queue_entry_t)p);
p = (vm_page_t) queue_next(&p->listq)) {
if (src_offset <= p->offset &&
p->offset < src_offset + size)
p->copy_on_write = TRUE;
}
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.
*/
p = (vm_page_t) queue_first(&src_object->memq);
while (!queue_end(&src_object->memq, (queue_entry_t) p)) {
if ((new_start <= p->offset) && (p->offset < new_end))
p->copy_on_write = TRUE;
p = (vm_page_t) queue_next(&p->listq);
}
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 lint
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)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 queue_t bucket;
register vm_object_hash_entry_t entry;
vm_object_t object;
bucket = &vm_object_hashtable[vm_object_hash(pager)];
vm_object_cache_lock();
entry = (vm_object_hash_entry_t) queue_first(bucket);
while (!queue_end(bucket, (queue_entry_t) entry)) {
object = entry->object;
if (object->pager == pager) {
vm_object_lock(object);
if (object->ref_count == 0) {
queue_remove(&vm_object_cached_list, object,
vm_object_t, cached_list);
vm_object_cached--;
}
object->ref_count++;
vm_object_unlock(object);
vm_object_cache_unlock();
return(object);
}
entry = (vm_object_hash_entry_t) queue_next(&entry->hash_links);
}
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;
{
register queue_t 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->can_persist = TRUE;
vm_object_cache_lock();
queue_enter(bucket, entry, vm_object_hash_entry_t, 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.
*/
vm_object_remove(pager)
register vm_pager_t pager;
{
register queue_t bucket;
register vm_object_hash_entry_t entry;
register vm_object_t object;
bucket = &vm_object_hashtable[vm_object_hash(pager)];
entry = (vm_object_hash_entry_t) queue_first(bucket);
while (!queue_end(bucket, (queue_entry_t) entry)) {
object = entry->object;
if (object->pager == pager) {
queue_remove(bucket, entry, vm_object_hash_entry_t,
hash_links);
free((caddr_t)entry, M_VMOBJHASH);
break;
}
entry = (vm_object_hash_entry_t) queue_next(&entry->hash_links);
}
}
/*
* 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 (!queue_empty(&vm_object_cached_list)) {
object = (vm_object_t) queue_first(&vm_object_cached_list);
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->internal ||
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 (!queue_empty(&backing_object->memq)) {
p = (vm_page_t)
queue_first(&backing_object->memq);
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->fake) {
vm_page_lock_queues();
vm_page_free(p);
vm_page_unlock_queues();
}
else {
if (pp) {
#if 1
/*
* This should never happen -- the
* parent cannot have ever had an
* external memory object, and thus
* cannot have absent pages.
*/
panic("vm_object_collapse: bad case");
/* andrew@werple.apana.org.au - from
mach 3.0 VM */
#else
/* may be someone waiting for it */
PAGE_WAKEUP(pp);
vm_page_lock_queues();
vm_page_free(pp);
vm_page_unlock_queues();
#endif
}
/*
* Parent now has no page.
* Move the backing object's page
* up.
*/
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.
*/
object->pager = backing_object->pager;
#if 1
/* Mach 3.0 code */
/* andrew@werple.apana.org.au, 12 Feb 1993 */
/*
* If there is no pager, leave paging-offset alone.
*/
if (object->pager)
object->paging_offset =
backing_object->paging_offset +
backing_offset;
#else
/* old VM 2.5 version */
object->paging_offset += backing_offset;
#endif
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);
queue_remove(&vm_object_list, backing_object,
vm_object_t, 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.
*/
p = (vm_page_t) queue_first(&backing_object->memq);
while (!queue_end(&backing_object->memq,
(queue_entry_t) p)) {
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->fake)) {
/*
* Page still needed.
* Can't go any further.
*/
vm_object_unlock(backing_object);
return;
}
p = (vm_page_t) queue_next(&p->listq);
}
/*
* 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.
*/
vm_object_reference(object->shadow = backing_object->shadow);
object->shadow_offset += backing_object->shadow_offset;
#if 1
/* Mach 3.0 code */
/* andrew@werple.apana.org.au, 12 Feb 1993 */
/*
* Backing object might have had a copy pointer
* to us. If it did, clear it.
*/
if (backing_object->copy == object)
backing_object->copy = NULL;
#endif
/* 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;
p = (vm_page_t) queue_first(&object->memq);
while (!queue_end(&object->memq, (queue_entry_t) p)) {
next = (vm_page_t) queue_next(&p->listq);
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();
}
p = next;
}
}
/*
* 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 lint
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);
}
#if defined(DEBUG) || (NDDB > 0)
/*
* vm_object_print: [ debug ]
*/
void vm_object_print(object, full)
vm_object_t object;
boolean_t full;
{
register vm_page_t p;
extern indent;
register int count;
if (object == NULL)
return;
iprintf("Object 0x%x: size=0x%x, res=%d, ref=%d, ",
(int) object, (int) object->size,
object->resident_page_count, object->ref_count);
printf("pager=0x%x+0x%x, shadow=(0x%x)+0x%x\n",
(int) object->pager, (int) object->paging_offset,
(int) object->shadow, (int) object->shadow_offset);
printf("cache: next=0x%x, prev=0x%x\n",
object->cached_list.next, object->cached_list.prev);
if (!full)
return;
indent += 2;
count = 0;
p = (vm_page_t) queue_first(&object->memq);
while (!queue_end(&object->memq, (queue_entry_t) p)) {
if (count == 0)
iprintf("memory:=");
else if (count == 6) {
printf("\n");
iprintf(" ...");
count = 0;
} else
printf(",");
count++;
printf("(off=0x%x,page=0x%x)", p->offset, VM_PAGE_TO_PHYS(p));
p = (vm_page_t) queue_next(&p->listq);
}
if (count != 0)
printf("\n");
indent -= 2;
}
#endif /* defined(DEBUG) || (NDDB > 0) */
Continuous source code history from original PDP-7 UNIX to FreeBSD 2, the first fully unencumbered FreeBSD release.