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freebsd-skq/sys/vm/vm_object.c
David Greenman 24a1cce34f NOTE: libkvm, w, ps, 'top', and any other utility which depends on struct 
proc or any VM system structure will have to be rebuilt!!!

Much needed overhaul of the VM system. Included in this first round of
changes:

1) Improved pager interfaces: init, alloc, dealloc, getpages, putpages,
   haspage, and sync operations are supported. The haspage interface now
   provides information about clusterability. All pager routines now take
   struct vm_object's instead of "pagers".

2) Improved data structures. In the previous paradigm, there is constant
   confusion caused by pagers being both a data structure ("allocate a
   pager") and a collection of routines. The idea of a pager structure has
   escentially been eliminated. Objects now have types, and this type is
   used to index the appropriate pager. In most cases, items in the pager
   structure were duplicated in the object data structure and thus were
   unnecessary. In the few cases that remained, a un_pager structure union
   was created in the object to contain these items.

3) Because of the cleanup of #1 & #2, a lot of unnecessary layering can now
   be removed. For instance, vm_object_enter(), vm_object_lookup(),
   vm_object_remove(), and the associated object hash list were some of the
   things that were removed.

4) simple_lock's removed. Discussion with several people reveals that the
   SMP locking primitives used in the VM system aren't likely the mechanism
   that we'll be adopting. Even if it were, the locking that was in the code
   was very inadequate and would have to be mostly re-done anyway. The
   locking in a uni-processor kernel was a no-op but went a long way toward
   making the code difficult to read and debug.

5) Places that attempted to kludge-up the fact that we don't have kernel
   thread support have been fixed to reflect the reality that we are really
   dealing with processes, not threads. The VM system didn't have complete
   thread support, so the comments and mis-named routines were just wrong.
   We now use tsleep and wakeup directly in the lock routines, for instance.

6) Where appropriate, the pagers have been improved, especially in the
   pager_alloc routines. Most of the pager_allocs have been rewritten and
   are now faster and easier to maintain.

7) The pagedaemon pageout clustering algorithm has been rewritten and
   now tries harder to output an even number of pages before and after
   the requested page. This is sort of the reverse of the ideal pagein
   algorithm and should provide better overall performance.

8) Unnecessary (incorrect) casts to caddr_t in calls to tsleep & wakeup
   have been removed. Some other unnecessary casts have also been removed.

9) Some almost useless debugging code removed.

10) Terminology of shadow objects vs. backing objects straightened out.
    The fact that the vm_object data structure escentially had this
    backwards really confused things. The use of "shadow" and "backing
    object" throughout the code is now internally consistent and correct
    in the Mach terminology.

11) Several minor bug fixes, including one in the vm daemon that caused
    0 RSS objects to not get purged as intended.

12) A "default pager" has now been created which cleans up the transition
    of objects to the "swap" type. The previous checks throughout the code
    for swp->pg_data != NULL were really ugly. This change also provides
    the rudiments for future backing of "anonymous" memory by something
    other than the swap pager (via the vnode pager, for example), and it
    allows the decision about which of these pagers to use to be made
    dynamically (although will need some additional decision code to do
    this, of course).

13) (dyson) MAP_COPY has been deprecated and the corresponding "copy
    object" code has been removed. MAP_COPY was undocumented and non-
    standard. It was furthermore broken in several ways which caused its
    behavior to degrade to MAP_PRIVATE. Binaries that use MAP_COPY will
    continue to work correctly, but via the slightly different semantics
    of MAP_PRIVATE.

14) (dyson) Sharing maps have been removed. It's marginal usefulness in a
    threads design can be worked around in other ways. Both #12 and #13
    were done to simplify the code and improve readability and maintain-
    ability. (As were most all of these changes)

TODO:

1) Rewrite most of the vnode pager to use VOP_GETPAGES/PUTPAGES. Doing
   this will reduce the vnode pager to a mere fraction of its current size.

2) Rewrite vm_fault and the swap/vnode pagers to use the clustering
   information provided by the new haspage pager interface. This will
   substantially reduce the overhead by eliminating a large number of
   VOP_BMAP() calls. The VOP_BMAP() filesystem interface should be
   improved to provide both a "behind" and "ahead" indication of
   contiguousness.

3) Implement the extended features of pager_haspage in swap_pager_haspage().
   It currently just says 0 pages ahead/behind.

4) Re-implement the swap device (swstrategy) in a more elegant way, perhaps
   via a much more general mechanism that could also be used for disk
   striping of regular filesystems.

5) Do something to improve the architecture of vm_object_collapse(). The
   fact that it makes calls into the swap pager and knows too much about
   how the swap pager operates really bothers me. It also doesn't allow
   for collapsing of non-swap pager objects ("unnamed" objects backed by
   other pagers).
1995-07-13 08:48:48 +00:00

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/*
* 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.
*
* from: @(#)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.
*
* $Id: vm_object.c,v 1.48 1995/06/11 19:31:53 rgrimes Exp $
*/
/*
* Virtual memory object module.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/proc.h> /* for curproc, pageproc */
#include <sys/malloc.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <vm/vm.h>
#include <vm/vm_page.h>
#include <vm/vm_pageout.h>
#include <vm/vm_pager.h>
#include <vm/swap_pager.h>
#include <vm/vm_kern.h>
static void _vm_object_allocate(objtype_t, vm_size_t, vm_object_t);
/*
* 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;
int vm_object_cache_max;
long object_collapses;
long object_bypasses;
static void
_vm_object_allocate(type, size, object)
objtype_t type;
vm_size_t size;
register vm_object_t object;
{
TAILQ_INIT(&object->memq);
TAILQ_INIT(&object->shadow_head);
object->type = type;
object->size = size;
object->ref_count = 1;
object->flags = 0;
object->paging_in_progress = 0;
object->resident_page_count = 0;
object->pg_data = NULL;
object->handle = NULL;
object->paging_offset = 0;
object->backing_object = NULL;
object->backing_object_offset = (vm_offset_t) 0;
object->last_read = 0;
TAILQ_INSERT_TAIL(&vm_object_list, object, object_list);
vm_object_count++;
}
/*
* vm_object_init:
*
* Initialize the VM objects module.
*/
void
vm_object_init(vm_offset_t nothing)
{
register int i;
TAILQ_INIT(&vm_object_cached_list);
TAILQ_INIT(&vm_object_list);
vm_object_count = 0;
vm_object_cache_max = 84;
if (cnt.v_page_count > 1000)
vm_object_cache_max += (cnt.v_page_count - 1000) / 4;
kernel_object = &kernel_object_store;
_vm_object_allocate(OBJT_DEFAULT, VM_MAX_KERNEL_ADDRESS - VM_MIN_KERNEL_ADDRESS,
kernel_object);
kmem_object = &kmem_object_store;
_vm_object_allocate(OBJT_DEFAULT, VM_MAX_KERNEL_ADDRESS - VM_MIN_KERNEL_ADDRESS,
kmem_object);
}
/*
* vm_object_allocate:
*
* Returns a new object with the given size.
*/
vm_object_t
vm_object_allocate(type, size)
objtype_t type;
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(type, size, result);
return (result);
}
/*
* vm_object_reference:
*
* Gets another reference to the given object.
*/
inline void
vm_object_reference(object)
register vm_object_t object;
{
if (object == NULL)
return;
if (object->ref_count == 0) {
if ((object->flags & OBJ_CANPERSIST) == 0)
panic("vm_object_reference: non-persistent object with 0 ref_count");
TAILQ_REMOVE(&vm_object_cached_list, object, cached_list);
vm_object_cached--;
}
object->ref_count++;
}
/*
* 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)
vm_object_t object;
{
vm_object_t temp;
while (object != NULL) {
if (object->ref_count == 0)
panic("vm_object_deallocate: object deallocated too many times");
/*
* Lose the reference
*/
object->ref_count--;
if (object->ref_count != 0) {
if ((object->ref_count == 1) &&
(object->handle == NULL) &&
(object->type == OBJT_DEFAULT ||
object->type == OBJT_SWAP)) {
vm_object_t robject;
robject = object->shadow_head.tqh_first;
if ((robject != NULL) &&
(robject->handle == NULL) &&
(robject->type == OBJT_DEFAULT ||
robject->type == OBJT_SWAP)) {
int s;
robject->ref_count += 2;
object->ref_count += 2;
do {
s = splhigh();
while (robject->paging_in_progress) {
robject->flags |= OBJ_PIPWNT;
tsleep(robject, PVM, "objde1", 0);
}
while (object->paging_in_progress) {
object->flags |= OBJ_PIPWNT;
tsleep(object, PVM, "objde2", 0);
}
splx(s);
} while( object->paging_in_progress || robject->paging_in_progress);
object->ref_count -= 2;
robject->ref_count -= 2;
if( robject->ref_count == 0) {
robject->ref_count += 1;
object = robject;
continue;
}
vm_object_collapse(robject);
return;
}
}
/*
* If there are still references, then we are done.
*/
return;
}
if (object->type == OBJT_VNODE) {
struct vnode *vp = object->handle;
vp->v_flag &= ~VTEXT;
}
/*
* See if this object can persist and has some resident
* pages. If so, enter it in the cache.
*/
if (object->flags & OBJ_CANPERSIST) {
if (object->resident_page_count != 0) {
vm_object_page_clean(object, 0, 0 ,TRUE, TRUE);
TAILQ_INSERT_TAIL(&vm_object_cached_list, object,
cached_list);
vm_object_cached++;
vm_object_cache_trim();
return;
} else {
object->flags &= ~OBJ_CANPERSIST;
}
}
/*
* Make sure no one uses us.
*/
object->flags |= OBJ_DEAD;
temp = object->backing_object;
if (temp)
TAILQ_REMOVE(&temp->shadow_head, object, shadow_list);
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, next;
vm_object_t backing_object;
int s;
/*
* wait for the pageout daemon to be done with the object
*/
s = splhigh();
while (object->paging_in_progress) {
object->flags |= OBJ_PIPWNT;
tsleep(object, PVM, "objtrm", 0);
}
splx(s);
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->type == OBJT_VNODE) {
struct vnode *vp = object->handle;
VOP_LOCK(vp);
vm_object_page_clean(object, 0, 0, TRUE, FALSE);
vinvalbuf(vp, V_SAVE, NOCRED, NULL, 0, 0);
VOP_UNLOCK(vp);
}
/*
* Now free the pages. For internal objects, this also removes them
* from paging queues.
*/
while ((p = object->memq.tqh_first) != NULL) {
if (p->flags & PG_BUSY)
printf("vm_object_terminate: freeing busy page\n");
PAGE_WAKEUP(p);
vm_page_free(p);
cnt.v_pfree++;
}
/*
* Let the pager know object is dead.
*/
vm_pager_deallocate(object);
TAILQ_REMOVE(&vm_object_list, object, object_list);
vm_object_count--;
wakeup(object);
/*
* 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.
*/
void
vm_object_page_clean(object, start, end, syncio, lockflag)
vm_object_t object;
vm_offset_t start;
vm_offset_t end;
boolean_t syncio;
boolean_t lockflag;
{
register vm_page_t p;
register vm_offset_t tstart, tend;
int pass;
int pgcount, s;
int allclean;
int entireobj;
struct vnode *vp;
if (object->type != OBJT_VNODE || (object->flags & OBJ_WRITEABLE) == 0)
return;
vp = object->handle;
if (lockflag)
VOP_LOCK(vp);
if (start != end) {
start = trunc_page(start);
end = round_page(end);
}
pass = 0;
startover:
tstart = start;
if (end == 0) {
tend = object->size;
} else {
tend = end;
}
entireobj = 0;
if (tstart == 0 && tend == object->size) {
object->flags &= ~OBJ_WRITEABLE;
entireobj = 1;
}
pgcount = object->resident_page_count;
if (pass == 0 &&
(pgcount < 128 || pgcount > (object->size / (8 * PAGE_SIZE)))) {
allclean = 1;
for(; pgcount && (tstart < tend); tstart += PAGE_SIZE) {
p = vm_page_lookup(object, tstart);
if (!p)
continue;
--pgcount;
s = splhigh();
TAILQ_REMOVE(&object->memq, p, listq);
TAILQ_INSERT_TAIL(&object->memq, p, listq);
splx(s);
if (entireobj)
vm_page_protect(p, VM_PROT_READ);
if ((p->flags & (PG_BUSY|PG_CACHE)) || p->busy ||
p->valid == 0) {
continue;
}
vm_page_test_dirty(p);
if ((p->valid & p->dirty) != 0) {
vm_offset_t tincr;
tincr = vm_pageout_clean(p, VM_PAGEOUT_FORCE);
if( tincr) {
pgcount -= (tincr - 1);
tincr *= PAGE_SIZE;
tstart += tincr - PAGE_SIZE;
}
allclean = 0;
}
}
if (!allclean) {
pass = 1;
goto startover;
}
if (lockflag)
VOP_UNLOCK(vp);
return;
}
allclean = 1;
while ((p = object->memq.tqh_first) != NULL && pgcount > 0) {
if (p->flags & PG_CACHE) {
goto donext;
}
if (entireobj || (p->offset >= tstart && p->offset < tend)) {
if (entireobj)
vm_page_protect(p, VM_PROT_READ);
if (p->valid == 0) {
goto donext;
}
s = splhigh();
if ((p->flags & PG_BUSY) || p->busy) {
allclean = 0;
if (pass > 0) {
p->flags |= PG_WANTED;
tsleep(p, PVM, "objpcn", 0);
splx(s);
continue;
} else {
splx(s);
goto donext;
}
}
TAILQ_REMOVE(&object->memq, p, listq);
TAILQ_INSERT_TAIL(&object->memq, p, listq);
splx(s);
pgcount--;
vm_page_test_dirty(p);
if ((p->valid & p->dirty) != 0) {
vm_pageout_clean(p, VM_PAGEOUT_FORCE);
allclean = 0;
}
continue;
}
donext:
TAILQ_REMOVE(&object->memq, p, listq);
TAILQ_INSERT_TAIL(&object->memq, p, listq);
pgcount--;
}
if ((!allclean && (pass == 0)) ||
(entireobj && (object->flags & OBJ_WRITEABLE))) {
pass = 1;
if (entireobj)
object->flags &= ~OBJ_WRITEABLE;
goto startover;
}
if (lockflag)
VOP_UNLOCK(vp);
return;
}
/*
* 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_deactivate(p);
}
}
/*
* Trim the object cache to size.
*/
void
vm_object_cache_trim()
{
register vm_object_t object;
while (vm_object_cached > vm_object_cache_max) {
object = vm_object_cached_list.tqh_first;
vm_object_reference(object);
pager_cache(object, FALSE);
}
}
/*
* 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;
for (p = object->memq.tqh_first; p != NULL; p = p->listq.tqe_next) {
if ((start <= p->offset) && (p->offset < end)) {
vm_page_protect(p, VM_PROT_READ);
p->flags |= PG_COPYONWRITE;
}
}
}
/*
* 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;
int s;
if (object == NULL)
return;
++object->paging_in_progress;
again:
for (p = object->memq.tqh_first; p != NULL; p = p->listq.tqe_next) {
if ((start <= p->offset) && (p->offset < end)) {
s = splhigh();
if ((p->flags & PG_BUSY) || p->busy) {
p->flags |= PG_WANTED;
tsleep(p, PVM, "vmopmr", 0);
splx(s);
goto again;
}
splx(s);
vm_page_protect(p, VM_PROT_NONE);
}
}
vm_object_pip_wakeup(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;
}
/*
* Try to collapse the object before copying it.
*/
if (src_object->handle == NULL &&
(src_object->type == OBJT_DEFAULT ||
src_object->type == OBJT_SWAP))
vm_object_collapse(src_object);
/*
* 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;
*dst_object = src_object;
*dst_offset = src_offset;
/*
* Must make a shadow when write is desired
*/
*src_needs_copy = TRUE;
return;
}
/*
* 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(OBJT_DEFAULT, 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->backing_object = source;
if (source)
TAILQ_INSERT_TAIL(&result->backing_object->shadow_head, result, shadow_list);
/*
* Store the offset into the source object, and fix up the offset into
* the new object.
*/
result->backing_object_offset = *offset;
/*
* Return the new things
*/
*offset = 0;
*object = result;
}
/*
* this version of collapse allows the operation to occur earlier and
* when paging_in_progress is true for an object... This is not a complete
* operation, but should plug 99.9% of the rest of the leaks.
*/
static void
vm_object_qcollapse(object)
register vm_object_t object;
{
register vm_object_t backing_object;
register vm_offset_t backing_offset, new_offset;
register vm_page_t p, pp;
register vm_size_t size;
backing_object = object->backing_object;
if (backing_object->ref_count != 1)
return;
backing_object->ref_count += 2;
backing_offset = object->backing_object_offset;
size = object->size;
p = backing_object->memq.tqh_first;
while (p) {
vm_page_t next;
next = p->listq.tqe_next;
if ((p->flags & (PG_BUSY | PG_FICTITIOUS | PG_CACHE)) ||
!p->valid || p->hold_count || p->wire_count || p->busy) {
p = next;
continue;
}
vm_page_protect(p, VM_PROT_NONE);
new_offset = (p->offset - backing_offset);
if (p->offset < backing_offset ||
new_offset >= size) {
if (backing_object->type == OBJT_SWAP)
swap_pager_freespace(backing_object,
backing_object->paging_offset + p->offset, PAGE_SIZE);
vm_page_free(p);
} else {
pp = vm_page_lookup(object, new_offset);
if (pp != NULL || (object->type == OBJT_SWAP && vm_pager_has_page(object,
object->paging_offset + new_offset, NULL, NULL))) {
if (backing_object->type == OBJT_SWAP)
swap_pager_freespace(backing_object,
backing_object->paging_offset + p->offset, PAGE_SIZE);
vm_page_free(p);
} else {
if (backing_object->type == OBJT_SWAP)
swap_pager_freespace(backing_object,
backing_object->paging_offset + p->offset, PAGE_SIZE);
vm_page_rename(p, object, new_offset);
p->dirty = VM_PAGE_BITS_ALL;
}
}
p = next;
}
backing_object->ref_count -= 2;
}
/*
* 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.
*/
void
vm_object_collapse(object)
vm_object_t object;
{
vm_object_t backing_object;
vm_offset_t backing_offset;
vm_size_t size;
vm_offset_t new_offset;
vm_page_t p, pp;
while (TRUE) {
/*
* Verify that the conditions are right for collapse:
*
* The object exists and no pages in it are currently being paged
* out.
*/
if (object == NULL)
return;
/*
* Make sure there is a backing object.
*/
if ((backing_object = object->backing_object) == NULL)
return;
/*
* we check the backing object first, because it is most likely
* not collapsable.
*/
if (backing_object->handle != NULL ||
(backing_object->type != OBJT_DEFAULT &&
backing_object->type != OBJT_SWAP) ||
(backing_object->flags & OBJ_DEAD) ||
object->handle != NULL ||
(object->type != OBJT_DEFAULT &&
object->type != OBJT_SWAP) ||
(object->flags & OBJ_DEAD)) {
return;
}
if (object->paging_in_progress != 0 ||
backing_object->paging_in_progress != 0) {
vm_object_qcollapse(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->backing_object_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) {
backing_object->flags |= OBJ_DEAD;
/*
* 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) != 0) {
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_protect(p, VM_PROT_NONE);
PAGE_WAKEUP(p);
vm_page_free(p);
} else {
pp = vm_page_lookup(object, new_offset);
if (pp != NULL || (object->type == OBJT_SWAP && vm_pager_has_page(object,
object->paging_offset + new_offset, NULL, NULL))) {
vm_page_protect(p, VM_PROT_NONE);
PAGE_WAKEUP(p);
vm_page_free(p);
} else {
vm_page_rename(p, object, new_offset);
}
}
}
/*
* Move the pager from backing_object to object.
*/
if (backing_object->type == OBJT_SWAP) {
backing_object->paging_in_progress++;
if (object->type == OBJT_SWAP) {
object->paging_in_progress++;
/*
* copy shadow object pages into ours
* and destroy unneeded pages in
* shadow object.
*/
swap_pager_copy(
backing_object, backing_object->paging_offset,
object, object->paging_offset,
object->backing_object_offset);
vm_object_pip_wakeup(object);
} else {
extern struct pagerlst swap_pager_un_object_list;
object->paging_in_progress++;
/*
* move the shadow backing_object's pager data to
* "object" and convert "object" type to OBJT_SWAP.
*/
object->type = OBJT_SWAP;
object->pg_data = backing_object->pg_data;
object->paging_offset = backing_object->paging_offset + backing_offset;
TAILQ_INSERT_TAIL(&swap_pager_un_object_list, object, pager_object_list);
/*
* Convert backing object from OBJT_SWAP to
* OBJT_DEFAULT. XXX - only the TAILQ_REMOVE is
* actually necessary.
*/
backing_object->type = OBJT_DEFAULT;
backing_object->pg_data = NULL;
TAILQ_REMOVE(&swap_pager_un_object_list, backing_object, pager_object_list);
/*
* free unnecessary blocks
*/
swap_pager_freespace(object, 0, object->paging_offset);
vm_object_pip_wakeup(object);
}
vm_object_pip_wakeup(backing_object);
}
/*
* Object now shadows whatever backing_object did.
* Note that the reference to backing_object->backing_object
* moves from within backing_object to within object.
*/
TAILQ_REMOVE(&object->backing_object->shadow_head, object,
shadow_list);
if (backing_object->backing_object)
TAILQ_REMOVE(&backing_object->backing_object->shadow_head,
backing_object, shadow_list);
object->backing_object = backing_object->backing_object;
if (object->backing_object)
TAILQ_INSERT_TAIL(&object->backing_object->shadow_head,
object, shadow_list);
object->backing_object_offset += backing_object->backing_object_offset;
/*
* 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.
*/
TAILQ_REMOVE(&vm_object_list, backing_object,
object_list);
vm_object_count--;
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->type != OBJT_DEFAULT) {
return;
}
/*
* Should have a check for a 'small' number of pages
* here.
*/
for (p = backing_object->memq.tqh_first; p; 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);
if ((pp == NULL || pp->valid == 0) &&
!vm_pager_has_page(object, object->paging_offset + new_offset, NULL, NULL)) {
/*
* Page still needed. Can't go any
* further.
*/
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.
*/
TAILQ_REMOVE(&object->backing_object->shadow_head,
object, shadow_list);
vm_object_reference(object->backing_object = backing_object->backing_object);
if (object->backing_object)
TAILQ_INSERT_TAIL(&object->backing_object->shadow_head,
object, shadow_list);
object->backing_object_offset += backing_object->backing_object_offset;
/*
* 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.
*/
if (backing_object->ref_count == 1)
printf("should have called obj deallocate\n");
backing_object->ref_count--;
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, clean_only)
register vm_object_t object;
register vm_offset_t start;
register vm_offset_t end;
boolean_t clean_only;
{
register vm_page_t p, next;
vm_offset_t size;
int s;
if (object == NULL)
return;
object->paging_in_progress++;
start = trunc_page(start);
end = round_page(end);
again:
size = end - start;
if (size > 4 * PAGE_SIZE || size >= object->size / 4) {
for (p = object->memq.tqh_first; p != NULL; p = next) {
next = p->listq.tqe_next;
if ((start <= p->offset) && (p->offset < end)) {
s = splhigh();
if (p->bmapped) {
splx(s);
continue;
}
if ((p->flags & PG_BUSY) || p->busy) {
p->flags |= PG_WANTED;
tsleep(p, PVM, "vmopar", 0);
splx(s);
goto again;
}
splx(s);
if (clean_only) {
vm_page_test_dirty(p);
if (p->valid & p->dirty)
continue;
}
vm_page_protect(p, VM_PROT_NONE);
PAGE_WAKEUP(p);
vm_page_free(p);
}
}
} else {
while (size > 0) {
while ((p = vm_page_lookup(object, start)) != 0) {
s = splhigh();
if (p->bmapped) {
splx(s);
break;
}
if ((p->flags & PG_BUSY) || p->busy) {
p->flags |= PG_WANTED;
tsleep(p, PVM, "vmopar", 0);
splx(s);
goto again;
}
splx(s);
if (clean_only) {
vm_page_test_dirty(p);
if (p->valid & p->dirty)
continue;
}
vm_page_protect(p, VM_PROT_NONE);
PAGE_WAKEUP(p);
vm_page_free(p);
}
start += PAGE_SIZE;
size -= PAGE_SIZE;
}
}
vm_object_pip_wakeup(object);
}
/*
* 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;
if (next_object != NULL) {
return (FALSE);
}
if (prev_object == NULL) {
return (TRUE);
}
/*
* 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->type != OBJT_DEFAULT ||
prev_object->backing_object != NULL) {
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, FALSE);
/*
* Extend the object if necessary.
*/
newsize = prev_offset + prev_size + next_size;
if (newsize > prev_object->size)
prev_object->size = newsize;
return (TRUE);
}
/*
* returns page after looking up in shadow chain
*/
vm_page_t
vm_object_page_lookup(object, offset)
vm_object_t object;
vm_offset_t offset;
{
vm_page_t m;
if (!(m = vm_page_lookup(object, offset))) {
if (!object->backing_object)
return 0;
else
return vm_object_page_lookup(object->backing_object, offset + object->backing_object_offset);
}
return m;
}
#ifdef DDB
int
_vm_object_in_map(map, object, entry)
vm_map_t map;
vm_object_t object;
vm_map_entry_t entry;
{
vm_map_t tmpm;
vm_map_entry_t tmpe;
vm_object_t obj;
int entcount;
if (map == 0)
return 0;
if (entry == 0) {
tmpe = map->header.next;
entcount = map->nentries;
while (entcount-- && (tmpe != &map->header)) {
if( _vm_object_in_map(map, object, tmpe)) {
return 1;
}
tmpe = tmpe->next;
}
} else if (entry->is_sub_map || entry->is_a_map) {
tmpm = entry->object.share_map;
tmpe = tmpm->header.next;
entcount = tmpm->nentries;
while (entcount-- && tmpe != &tmpm->header) {
if( _vm_object_in_map(tmpm, object, tmpe)) {
return 1;
}
tmpe = tmpe->next;
}
} else if (obj = entry->object.vm_object) {
for(; obj; obj=obj->backing_object)
if( obj == object) {
return 1;
}
}
return 0;
}
int
vm_object_in_map( object)
vm_object_t object;
{
struct proc *p;
for (p = (struct proc *) allproc; p != NULL; p = p->p_next) {
if( !p->p_vmspace /* || (p->p_flag & (P_SYSTEM|P_WEXIT)) */)
continue;
/*
if (p->p_stat != SRUN && p->p_stat != SSLEEP) {
continue;
}
*/
if( _vm_object_in_map(&p->p_vmspace->vm_map, object, 0))
return 1;
}
if( _vm_object_in_map( kernel_map, object, 0))
return 1;
if( _vm_object_in_map( kmem_map, object, 0))
return 1;
if( _vm_object_in_map( pager_map, object, 0))
return 1;
if( _vm_object_in_map( buffer_map, object, 0))
return 1;
if( _vm_object_in_map( io_map, object, 0))
return 1;
if( _vm_object_in_map( phys_map, object, 0))
return 1;
if( _vm_object_in_map( mb_map, object, 0))
return 1;
if( _vm_object_in_map( u_map, object, 0))
return 1;
return 0;
}
void
vm_object_check() {
int i;
int maxhash = 0;
vm_object_t object;
/*
* make sure that internal objs are in a map somewhere
* and none have zero ref counts.
*/
for (object = vm_object_list.tqh_first;
object != NULL;
object = object->object_list.tqe_next) {
if (object->handle == NULL &&
(object->type == OBJT_DEFAULT || object->type == OBJT_SWAP)) {
if (object->ref_count == 0) {
printf("vmochk: internal obj has zero ref count: %d\n",
object->size);
}
if (!vm_object_in_map(object)) {
printf("vmochk: internal obj is not in a map: ref: %d, size: %d, pg_data: 0x%x, backing_object: 0x%x\n",
object->ref_count, object->size, object->pg_data, object->backing_object);
}
}
}
}
/*
* vm_object_print: [ debug ]
*/
void
vm_object_print(object, full)
vm_object_t object;
boolean_t full;
{
register vm_page_t p;
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("pg_data=0x%x+0x%x, backing_object=(0x%x)+0x%x\n",
(int) object->pg_data, (int) object->paging_offset,
(int) object->backing_object, (int) object->backing_object_offset);
printf("cache: next=%p, prev=%p\n",
object->cached_list.tqe_next, 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("memory:=");
else if (count == 6) {
printf("\n");
iprintf(" ...");
count = 0;
} else
printf(",");
count++;
printf("(off=0x%lx,page=0x%lx)",
(u_long) p->offset, (u_long) VM_PAGE_TO_PHYS(p));
}
if (count != 0)
printf("\n");
indent -= 2;
}
#endif /* DDB */
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