uvm_anon.h revision 1.4 1 /* $NetBSD: uvm_anon.h,v 1.4 1998/02/09 04:05:36 mrg Exp $ */
2
3 /*
4 * XXXCDC: "ROUGH DRAFT" QUALITY UVM PRE-RELEASE FILE!
5 * >>>USE AT YOUR OWN RISK, WORK IS NOT FINISHED<<<
6 */
7 /*
8 *
9 * Copyright (c) 1997 Charles D. Cranor and Washington University.
10 * All rights reserved.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. All advertising materials mentioning features or use of this software
21 * must display the following acknowledgement:
22 * This product includes software developed by Charles D. Cranor and
23 * Washington University.
24 * 4. The name of the author may not be used to endorse or promote products
25 * derived from this software without specific prior written permission.
26 *
27 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
28 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
29 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
30 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
31 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
32 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
33 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
34 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
35 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
36 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
37 *
38 * from: Id: uvm_anon.h,v 1.1.2.4 1998/01/04 22:43:39 chuck Exp
39 */
40
41 /*
42 * uvm_anon.h
43 */
44
45 /*
46 * anonymous memory management
47 *
48 * anonymous virtual memory is short term virtual memory that goes away
49 * when the processes referencing it go away. an anonymous page of
50 * virtual memory is described by the following data structure:
51 */
52
53 struct vm_anon {
54 int an_ref; /* reference count [an_lock] */
55 #if NCPU > 1
56 simple_lock_data_t an_lock; /* lock for an_ref */
57 #endif
58 union {
59 struct vm_anon *an_nxt; /* if on free list [afreelock] */
60 struct vm_page *an_page;/* if in RAM [pageqlock] */
61 } u;
62 int an_swslot; /* drum swap slot # (if != 0) [pageqlock] */
63 };
64
65 /*
66 * a pool of vm_anon data structures is allocated and put on a global
67 * free list at boot time. vm_anon's on the free list use "an_nxt" as
68 * a pointer to the next item on the free list. for active vm_anon's
69 * the data can be in one of the following state: [1] in a vm_page
70 * with no backing store allocated yet, [2] in a vm_page with backing
71 * store allocated, or [3] paged out to backing store (no vm_page).
72 *
73 * for pageout in case [2]: if the page has been modified then we must
74 * flush it out to backing store, otherwise we can just dump the
75 * vm_page.
76 */
77
78 /*
79 * anonymous virtual memory pages (vm_anon's) live in anonymous memory
80 * maps. anonymous memory maps can be shared between processes.
81 * different subsets of an anonymous memory map can be referenced by
82 * processes (see below). an anonymous map is described by the following
83 * data structure:
84 */
85
86 #define VM_AMAP_PPREF /* use a per-page reference count for split
87 vm_map_entry_t's. */
88
89 struct vm_amap {
90 #if NCPU > 1
91 simple_lock_data_t am_l; /* simple lock [locks all vm_amap fields] */
92 #endif
93 int am_ref; /* reference count */
94 int am_flags; /* flags */
95 int am_maxslot; /* max # of slots allocated */
96 int am_nslot; /* # of slots currently in map ( <= maxslot) */
97 int am_nused; /* # of slots currently in use */
98 int *am_slots; /* contig array of active slots */
99 int *am_bckptr; /* back pointer array to am_slots */
100 struct vm_anon **am_anon; /* array of anonymous pages */
101 #ifdef VM_AMAP_PPREF
102 int *am_ppref; /* per page reference count (if !NULL) */
103 #endif
104 };
105
106 #define AMAP_SHARED 0x1 /* am_flags: shared amap */
107 #define AMAP_REFALL 0x2 /* flag to amap_ref() */
108
109 /*
110 * note that am_slots, am_bckptr, and am_anon are arrays. this allows
111 * fast lookup of pages based on their virual address at the expense of
112 * some extra memory. [XXX: for memory starved systems provide alternate
113 * functions?]
114 *
115 * 4 slot/page example, with slots 1 and 3 in use:
116 * ("D/C" == don't care what the value is)
117 *
118 * 0 1 2 3
119 * am_anon: NULL, anon0, NULL, anon1 (actual pointers to anons)
120 * am_bckptr: D/C, 1, D/C, 0 (points to am_slots entry)
121 *
122 * am_slots: 3, 1, D/C, D/C (says slots 3 and 1 are in use)
123 *
124 * note that am_bckptr is D/C if the slot in am_anon is set to NULL.
125 * to find the entry in am_slots for an anon, look at am_bckptr[slot],
126 * thus the entry for slot 3 in am_slots[] is at am_slots[am_bckptr[3]].
127 * in general, if am_anon[X] is non-NULL, then the following must be
128 * true: am_slots[am_bckptr[X]] == X
129 *
130 * note that am_slots is always contig-packed.
131 */
132
133 /*
134 * processes reference anonymous virtual memory maps with an anonymous
135 * reference structure:
136 */
137
138 struct vm_aref {
139 int ar_slotoff; /* slot offset into amap we start */
140 struct vm_amap *ar_amap; /* pointer to amap */
141 };
142
143 /*
144 * the offset field indicates which part of the amap we are referencing.
145 * locked by vm_map lock.
146 */
147
148