1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
|
/*
* Mach Operating System
* Copyright (c) 1991,1990,1989 Carnegie Mellon University
* All Rights Reserved.
*
* 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 Mellon
* the rights to redistribute these changes.
*/
/*
* This module maintains information about the presence of
* pages not in memory. Since an external memory object
* must maintain a complete knowledge of its contents, this
* information takes the form of hints.
*/
#include <mach/boolean.h>
#include <kern/slab.h>
#include <vm/vm_external.h>
#include <mach/vm_param.h>
#include <kern/assert.h>
boolean_t vm_external_unsafe = FALSE;
struct kmem_cache vm_external_cache;
/*
* The implementation uses bit arrays to record whether
* a page has been written to external storage. For
* convenience, these bit arrays come in two sizes
* (measured in bytes).
*/
#define SMALL_SIZE (VM_EXTERNAL_SMALL_SIZE/8)
#define LARGE_SIZE (VM_EXTERNAL_LARGE_SIZE/8)
struct kmem_cache vm_object_small_existence_map_cache;
struct kmem_cache vm_object_large_existence_map_cache;
vm_external_t vm_external_create(vm_offset_t size)
{
vm_external_t result;
vm_size_t bytes;
result = (vm_external_t) kmem_cache_alloc(&vm_external_cache);
result->existence_map = (char *) 0;
bytes = (atop(size) + 07) >> 3;
if (bytes <= SMALL_SIZE) {
result->existence_map =
(char *) kmem_cache_alloc(&vm_object_small_existence_map_cache);
result->existence_size = SMALL_SIZE;
} else if (bytes <= LARGE_SIZE) {
result->existence_map =
(char *) kmem_cache_alloc(&vm_object_large_existence_map_cache);
result->existence_size = LARGE_SIZE;
}
return(result);
}
void vm_external_destroy(vm_external_t e)
{
if (e == VM_EXTERNAL_NULL)
return;
if (e->existence_map != (char *) 0) {
if (e->existence_size <= SMALL_SIZE) {
kmem_cache_free(&vm_object_small_existence_map_cache,
(vm_offset_t) e->existence_map);
} else {
kmem_cache_free(&vm_object_large_existence_map_cache,
(vm_offset_t) e->existence_map);
}
}
kmem_cache_free(&vm_external_cache, (vm_offset_t) e);
}
vm_external_state_t _vm_external_state_get(e, offset)
const vm_external_t e;
vm_offset_t offset;
{
unsigned
int bit, byte;
if (vm_external_unsafe ||
(e == VM_EXTERNAL_NULL) ||
(e->existence_map == (char *) 0))
return(VM_EXTERNAL_STATE_UNKNOWN);
bit = atop(offset);
byte = bit >> 3;
if (byte >= e->existence_size) return (VM_EXTERNAL_STATE_UNKNOWN);
return( (e->existence_map[byte] & (1 << (bit & 07))) ?
VM_EXTERNAL_STATE_EXISTS : VM_EXTERNAL_STATE_ABSENT );
}
void vm_external_state_set(
vm_external_t e,
vm_offset_t offset,
vm_external_state_t state)
{
unsigned
int bit, byte;
if ((e == VM_EXTERNAL_NULL) || (e->existence_map == (char *) 0))
return;
if (state != VM_EXTERNAL_STATE_EXISTS)
return;
bit = atop(offset);
byte = bit >> 3;
if (byte >= e->existence_size) return;
e->existence_map[byte] |= (1 << (bit & 07));
}
void vm_external_module_initialize(void)
{
vm_size_t size = (vm_size_t) sizeof(struct vm_external);
kmem_cache_init(&vm_external_cache, "vm_external", size, 0,
NULL, NULL, NULL, 0);
kmem_cache_init(&vm_object_small_existence_map_cache,
"small_existence_map", SMALL_SIZE, 0,
NULL, NULL, NULL, 0);
kmem_cache_init(&vm_object_large_existence_map_cache,
"large_existence_map", LARGE_SIZE, 0,
NULL, NULL, NULL, 0);
}
|
