c8b0a7332c
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).
176 lines
6.7 KiB
C
176 lines
6.7 KiB
C
/*
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* Copyright (c) 1991, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* The Mach Operating System project at Carnegie-Mellon University.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* from: @(#)vm_object.h 8.3 (Berkeley) 1/12/94
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*
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*
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* Copyright (c) 1987, 1990 Carnegie-Mellon University.
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* All rights reserved.
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*
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* Authors: Avadis Tevanian, Jr., Michael Wayne Young
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*
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* Permission to use, copy, modify and distribute this software and
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* its documentation is hereby granted, provided that both the copyright
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* notice and this permission notice appear in all copies of the
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* software, derivative works or modified versions, and any portions
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* thereof, and that both notices appear in supporting documentation.
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*
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* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
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* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
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* FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
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*
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* Carnegie Mellon requests users of this software to return to
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*
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* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
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* School of Computer Science
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* Carnegie Mellon University
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* Pittsburgh PA 15213-3890
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*
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* any improvements or extensions that they make and grant Carnegie the
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* rights to redistribute these changes.
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*
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* $Id: vm_object.h,v 1.18 1995/05/02 05:57:11 davidg Exp $
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*/
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/*
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* Virtual memory object module definitions.
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*/
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#ifndef _VM_OBJECT_
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#define _VM_OBJECT_
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#ifdef KERNEL
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#include <sys/proc.h> /* XXX for wakeup() */
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#endif
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enum obj_type { OBJT_DEFAULT, OBJT_SWAP, OBJT_VNODE, OBJT_DEVICE };
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typedef enum obj_type objtype_t;
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/*
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* Types defined:
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*
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* vm_object_t Virtual memory object.
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*/
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struct vm_object {
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TAILQ_ENTRY(vm_object) object_list; /* list of all objects */
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TAILQ_ENTRY(vm_object) cached_list; /* list of cached (persistent) objects */
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TAILQ_HEAD(, vm_object) shadow_head; /* objects that this is a shadow for */
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TAILQ_ENTRY(vm_object) shadow_list; /* chain of shadow objects */
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TAILQ_HEAD(, vm_page) memq; /* list of resident pages */
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objtype_t type; /* type of pager */
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vm_size_t size; /* Object size */
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int ref_count; /* How many refs?? */
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u_short flags; /* see below */
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u_short paging_in_progress; /* Paging (in or out) so don't collapse or destroy */
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int resident_page_count; /* number of resident pages */
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vm_offset_t paging_offset; /* Offset into paging space */
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struct vm_object *backing_object; /* object that I'm a shadow of */
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vm_offset_t backing_object_offset;/* Offset in backing object */
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struct vm_object *copy; /* Object that holds copies of my changed pages */
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vm_offset_t last_read; /* last read in object -- detect seq behavior */
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TAILQ_ENTRY(vm_object) pager_object_list; /* list of all objects of this pager type */
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void *handle;
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void *pg_data;
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union {
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struct {
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vm_size_t vnp_size; /* Current size of file */
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} vnp;
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struct {
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TAILQ_HEAD(, vm_page) devp_pglist; /* list of pages allocated */
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} devp;
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} un_pager;
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};
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/*
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* Flags
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*/
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#define OBJ_CANPERSIST 0x0001 /* allow to persist */
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#define OBJ_ACTIVE 0x0004 /* active objects */
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#define OBJ_DEAD 0x0008 /* dead objects (during rundown) */
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#define OBJ_PIPWNT 0x0040 /* paging in progress wanted */
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#define OBJ_WRITEABLE 0x0080 /* object has been made writable */
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#ifdef KERNEL
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extern int vm_object_cache_max;
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TAILQ_HEAD(object_q, vm_object);
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struct object_q vm_object_cached_list; /* list of objects persisting */
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int vm_object_cached; /* size of cached list */
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struct object_q vm_object_list; /* list of allocated objects */
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long vm_object_count; /* count of all objects */
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/* lock for object list and count */
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vm_object_t kernel_object; /* the single kernel object */
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vm_object_t kmem_object;
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#endif /* KERNEL */
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#ifdef KERNEL
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static __inline void
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vm_object_pip_wakeup(vm_object_t object)
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{
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object->paging_in_progress--;
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if ((object->flags & OBJ_PIPWNT) && object->paging_in_progress == 0) {
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object->flags &= ~OBJ_PIPWNT;
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wakeup(object);
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}
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}
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vm_object_t vm_object_allocate __P((objtype_t, vm_size_t));
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void vm_object_cache_clear __P((void));
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void vm_object_cache_trim __P((void));
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boolean_t vm_object_coalesce __P((vm_object_t, vm_object_t, vm_offset_t, vm_offset_t, vm_offset_t, vm_size_t));
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void vm_object_collapse __P((vm_object_t));
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void vm_object_copy __P((vm_object_t, vm_offset_t, vm_size_t, vm_object_t *, vm_offset_t *, boolean_t *));
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void vm_object_deactivate_pages __P((vm_object_t));
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void vm_object_deallocate __P((vm_object_t));
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void vm_object_init __P((vm_size_t));
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void vm_object_page_clean __P((vm_object_t, vm_offset_t, vm_offset_t, boolean_t, boolean_t));
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void vm_object_page_remove __P((vm_object_t, vm_offset_t, vm_offset_t, boolean_t));
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void vm_object_pmap_copy __P((vm_object_t, vm_offset_t, vm_offset_t));
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void vm_object_pmap_remove __P((vm_object_t, vm_offset_t, vm_offset_t));
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void vm_object_print __P((vm_object_t, boolean_t));
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void vm_object_reference __P((vm_object_t));
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void vm_object_shadow __P((vm_object_t *, vm_offset_t *, vm_size_t));
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void vm_object_terminate __P((vm_object_t));
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#endif /* KERNEL */
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#endif /* _VM_OBJECT_ */
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