kernel - simplify vm pager ops, add pre-faulting for zero-fill pages.
[dragonfly.git] / sys / vm / phys_pager.c
1 /*
2  * Copyright (c) 2000 Peter Wemm
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
7  * 1. Redistributions of source code must retain the above copyright
8  *    notice, this list of conditions and the following disclaimer.
9  * 2. Redistributions in binary form must reproduce the above copyright
10  *    notice, this list of conditions and the following disclaimer in the
11  *    documentation and/or other materials provided with the distribution.
12  *
13  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
14  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
16  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
17  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
18  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
19  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
20  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
21  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
22  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
23  * SUCH DAMAGE.
24  *
25  * $FreeBSD: src/sys/vm/phys_pager.c,v 1.3.2.3 2000/12/17 02:05:41 alfred Exp $
26  * $DragonFly: src/sys/vm/phys_pager.c,v 1.5 2006/03/27 01:54:18 dillon Exp $
27  */
28
29 #include <sys/param.h>
30 #include <sys/systm.h>
31 #include <sys/linker_set.h>
32 #include <sys/conf.h>
33 #include <sys/mman.h>
34 #include <sys/sysctl.h>
35
36 #include <vm/vm.h>
37 #include <vm/vm_object.h>
38 #include <vm/vm_page.h>
39 #include <vm/vm_pager.h>
40 #include <vm/vm_zone.h>
41
42 #include <sys/thread2.h>
43
44 /* list of device pager objects */
45 static struct pagerlst phys_pager_object_list;
46
47 static int phys_pager_alloc_lock, phys_pager_alloc_lock_want;
48
49 static void
50 phys_pager_init(void)
51 {
52
53         TAILQ_INIT(&phys_pager_object_list);
54 }
55
56 static vm_object_t
57 phys_pager_alloc(void *handle, off_t size, vm_prot_t prot, off_t foff)
58 {
59         vm_object_t object;
60
61         /*
62          * Offset should be page aligned.
63          */
64         if (foff & PAGE_MASK)
65                 return (NULL);
66
67         size = round_page(size);
68
69         if (handle != NULL) {
70                 /*
71                  * Lock to prevent object creation race condition.
72                  */
73                 while (phys_pager_alloc_lock) {
74                         phys_pager_alloc_lock_want++;
75                         tsleep(&phys_pager_alloc_lock, 0, "ppall", 0);
76                         phys_pager_alloc_lock_want--;
77                 }
78                 phys_pager_alloc_lock = 1;
79         
80                 /*
81                  * Look up pager, creating as necessary.
82                  */
83                 object = vm_pager_object_lookup(&phys_pager_object_list, handle);
84                 if (object == NULL) {
85                         /*
86                          * Allocate object and associate it with the pager.
87                          */
88                         object = vm_object_allocate(OBJT_PHYS,
89                                 OFF_TO_IDX(foff + size));
90                         object->handle = handle;
91                         TAILQ_INSERT_TAIL(&phys_pager_object_list, object,
92                             pager_object_list);
93                 } else {
94                         /*
95                          * Gain a reference to the object.
96                          */
97                         vm_object_reference(object);
98                         if (OFF_TO_IDX(foff + size) > object->size)
99                                 object->size = OFF_TO_IDX(foff + size);
100                 }
101                 phys_pager_alloc_lock = 0;
102                 if (phys_pager_alloc_lock_want)
103                         wakeup(&phys_pager_alloc_lock);
104         } else {
105                 object = vm_object_allocate(OBJT_PHYS,
106                         OFF_TO_IDX(foff + size));
107         }
108
109         return (object);
110 }
111
112 static void
113 phys_pager_dealloc(vm_object_t object)
114 {
115
116         if (object->handle != NULL)
117                 TAILQ_REMOVE(&phys_pager_object_list, object, pager_object_list);
118 }
119
120 static int
121 phys_pager_getpage(vm_object_t object, vm_page_t *mpp, int seqaccess)
122 {
123         vm_page_t m = *mpp;
124
125         crit_enter();
126         if ((m->flags & PG_ZERO) == 0)
127                 vm_page_zero_fill(m);
128         vm_page_flag_set(m, PG_ZERO);
129         /* Switch off pv_entries */
130         vm_page_unmanage(m);
131         m->valid = VM_PAGE_BITS_ALL;
132         m->dirty = 0;
133         crit_exit();
134
135         return (VM_PAGER_OK);
136 }
137
138 static void
139 phys_pager_putpages(vm_object_t object, vm_page_t *m, int count,
140                     boolean_t sync, int *rtvals)
141 {
142
143         panic("phys_pager_putpage called");
144 }
145
146 /*
147  * Implement a pretty aggressive clustered getpages strategy.  Hint that
148  * everything in an entire 4MB window should be prefaulted at once.
149  *
150  * XXX 4MB (1024 slots per page table page) is convenient for x86,
151  * but may not be for other arches.
152  */
153 #ifndef PHYSCLUSTER
154 #define PHYSCLUSTER 1024
155 #endif
156
157 static boolean_t
158 phys_pager_haspage(vm_object_t object, vm_pindex_t pindex)
159 {
160         return (TRUE);
161 }
162
163 struct pagerops physpagerops = {
164         phys_pager_init,
165         phys_pager_alloc,
166         phys_pager_dealloc,
167         phys_pager_getpage,
168         phys_pager_putpages,
169         phys_pager_haspage,
170         NULL
171 };