1 | /* $NetBSD: uvm_amap.h,v 1.37 2011/06/12 03:36:02 rmind Exp $ */ |
2 | |
3 | /* |
4 | * Copyright (c) 1997 Charles D. Cranor and Washington University. |
5 | * All rights reserved. |
6 | * |
7 | * Redistribution and use in source and binary forms, with or without |
8 | * modification, are permitted provided that the following conditions |
9 | * are met: |
10 | * 1. Redistributions of source code must retain the above copyright |
11 | * notice, this list of conditions and the following disclaimer. |
12 | * 2. Redistributions in binary form must reproduce the above copyright |
13 | * notice, this list of conditions and the following disclaimer in the |
14 | * documentation and/or other materials provided with the distribution. |
15 | * |
16 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
17 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
18 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
19 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
20 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
21 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
22 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
23 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
24 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
25 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
26 | */ |
27 | |
28 | #ifndef _UVM_UVM_AMAP_H_ |
29 | #define _UVM_UVM_AMAP_H_ |
30 | |
31 | /* |
32 | * uvm_amap.h: general amap interface and amap implementation-specific info |
33 | */ |
34 | |
35 | /* |
36 | * an amap structure contains pointers to a set of anons that are |
37 | * mapped together in virtual memory (an anon is a single page of |
38 | * anonymous virtual memory -- see uvm_anon.h). in uvm we hide the |
39 | * details of the implementation of amaps behind a general amap |
40 | * interface. this allows us to change the amap implementation |
41 | * without having to touch the rest of the code. this file is divided |
42 | * into two parts: the definition of the uvm amap interface and the |
43 | * amap implementation-specific definitions. |
44 | */ |
45 | |
46 | #ifdef _KERNEL |
47 | |
48 | /* |
49 | * part 1: amap interface |
50 | */ |
51 | |
52 | void uvm_amap_init(void); |
53 | |
54 | /* |
55 | * forward definition of vm_amap structure. only amap |
56 | * implementation-specific code should directly access the fields of |
57 | * this structure. |
58 | */ |
59 | |
60 | struct vm_amap; |
61 | |
62 | |
63 | /* |
64 | * prototypes for the amap interface |
65 | */ |
66 | |
67 | void amap_add /* add an anon to an amap */ |
68 | (struct vm_aref *, vaddr_t, |
69 | struct vm_anon *, bool); |
70 | struct vm_amap *amap_alloc /* allocate a new amap */ |
71 | (vaddr_t, vaddr_t, int); |
72 | void amap_copy /* clear amap needs-copy flag */ |
73 | (struct vm_map *, struct vm_map_entry *, int, |
74 | vaddr_t, vaddr_t); |
75 | void amap_cow_now /* resolve all COW faults now */ |
76 | (struct vm_map *, struct vm_map_entry *); |
77 | int amap_extend /* make amap larger */ |
78 | (struct vm_map_entry *, vsize_t, int); |
79 | int amap_flags /* get amap's flags */ |
80 | (struct vm_amap *); |
81 | void amap_free /* free amap */ |
82 | (struct vm_amap *); |
83 | void amap_lock /* lock amap */ |
84 | (struct vm_amap *); |
85 | struct vm_anon *amap_lookup /* lookup an anon @ offset in amap */ |
86 | (struct vm_aref *, vaddr_t); |
87 | void amap_lookups /* lookup multiple anons */ |
88 | (struct vm_aref *, vaddr_t, |
89 | struct vm_anon **, int); |
90 | void amap_ref /* add a reference to an amap */ |
91 | (struct vm_amap *, vaddr_t, vsize_t, int); |
92 | int amap_refs /* get number of references of amap */ |
93 | (struct vm_amap *); |
94 | void amap_share_protect /* protect pages in a shared amap */ |
95 | (struct vm_map_entry *, vm_prot_t); |
96 | void amap_splitref /* split reference to amap into two */ |
97 | (struct vm_aref *, struct vm_aref *, vaddr_t); |
98 | void amap_unadd /* remove an anon from an amap */ |
99 | (struct vm_aref *, vaddr_t); |
100 | void amap_unlock /* unlock amap */ |
101 | (struct vm_amap *); |
102 | void amap_unref /* drop reference to an amap */ |
103 | (struct vm_amap *, vaddr_t, vsize_t, bool); |
104 | void amap_wipeout /* remove all anons from amap */ |
105 | (struct vm_amap *); |
106 | bool amap_swap_off |
107 | (int, int); |
108 | |
109 | /* |
110 | * amap flag values |
111 | */ |
112 | |
113 | #define AMAP_SHARED 0x1 /* amap is shared */ |
114 | #define AMAP_REFALL 0x2 /* amap_ref: reference entire amap */ |
115 | #define AMAP_SWAPOFF 0x4 /* amap_swap_off() is in progress */ |
116 | |
117 | /* |
118 | * amap_copy flags |
119 | */ |
120 | |
121 | #define AMAP_COPY_NOWAIT 0x02 /* not allowed to sleep */ |
122 | #define AMAP_COPY_NOCHUNK 0x04 /* not allowed to chunk */ |
123 | #define AMAP_COPY_NOMERGE 0x08 /* not allowed to merge */ |
124 | |
125 | /* |
126 | * amap_extend flags |
127 | */ |
128 | #define AMAP_EXTEND_BACKWARDS 0x00 /* add "size" to start of map */ |
129 | #define AMAP_EXTEND_FORWARDS 0x01 /* add "size" to end of map */ |
130 | #define AMAP_EXTEND_NOWAIT 0x02 /* not allowed to sleep */ |
131 | |
132 | #endif /* _KERNEL */ |
133 | |
134 | /**********************************************************************/ |
135 | |
136 | /* |
137 | * part 2: amap implementation-specific info |
138 | */ |
139 | |
140 | /* |
141 | * we currently provide an array-based amap implementation. in this |
142 | * implementation we provide the option of tracking split references |
143 | * so that we don't lose track of references during partial unmaps |
144 | * ... this is enabled with the "UVM_AMAP_PPREF" define. |
145 | */ |
146 | |
147 | #define UVM_AMAP_PPREF /* track partial references */ |
148 | |
149 | /* |
150 | * here is the definition of the vm_amap structure for this implementation. |
151 | */ |
152 | |
153 | struct vm_amap { |
154 | kmutex_t *am_lock; /* lock [locks all vm_amap fields] */ |
155 | int am_ref; /* reference count */ |
156 | int am_flags; /* flags */ |
157 | int am_maxslot; /* max # of slots allocated */ |
158 | int am_nslot; /* # of slots currently in map ( <= maxslot) */ |
159 | int am_nused; /* # of slots currently in use */ |
160 | int *am_slots; /* contig array of active slots */ |
161 | int *am_bckptr; /* back pointer array to am_slots */ |
162 | struct vm_anon **am_anon; /* array of anonymous pages */ |
163 | #ifdef UVM_AMAP_PPREF |
164 | int *am_ppref; /* per page reference count (if !NULL) */ |
165 | #endif |
166 | LIST_ENTRY(vm_amap) am_list; |
167 | }; |
168 | |
169 | /* |
170 | * note that am_slots, am_bckptr, and am_anon are arrays. this allows |
171 | * fast lookup of pages based on their virual address at the expense of |
172 | * some extra memory. in the future we should be smarter about memory |
173 | * usage and fall back to a non-array based implementation on systems |
174 | * that are short of memory (XXXCDC). |
175 | * |
176 | * the entries in the array are called slots... for example an amap that |
177 | * covers four pages of virtual memory is said to have four slots. here |
178 | * is an example of the array usage for a four slot amap. note that only |
179 | * slots one and three have anons assigned to them. "D/C" means that we |
180 | * "don't care" about the value. |
181 | * |
182 | * 0 1 2 3 |
183 | * am_anon: NULL, anon0, NULL, anon1 (actual pointers to anons) |
184 | * am_bckptr: D/C, 1, D/C, 0 (points to am_slots entry) |
185 | * |
186 | * am_slots: 3, 1, D/C, D/C (says slots 3 and 1 are in use) |
187 | * |
188 | * note that am_bckptr is D/C if the slot in am_anon is set to NULL. |
189 | * to find the entry in am_slots for an anon, look at am_bckptr[slot], |
190 | * thus the entry for slot 3 in am_slots[] is at am_slots[am_bckptr[3]]. |
191 | * in general, if am_anon[X] is non-NULL, then the following must be |
192 | * true: am_slots[am_bckptr[X]] == X |
193 | * |
194 | * note that am_slots is always contig-packed. |
195 | */ |
196 | |
197 | /* |
198 | * defines for handling of large, sparse amaps: |
199 | * |
200 | * one of the problems of array-based amaps is that if you allocate a |
201 | * large, sparsely-used area of virtual memory you end up allocating |
202 | * large arrays that, for the most part, don't get used. this is a |
203 | * problem for BSD in that the kernel likes to make these types of |
204 | * allocations to "reserve" memory for possible future use. |
205 | * |
206 | * for example, the kernel allocates (reserves) a large chunk of user |
207 | * VM for possible stack growth. most of the time only a page or two |
208 | * of this VM is actually used. since the stack is anonymous memory |
209 | * it makes sense for it to live in an amap, but if we allocated an |
210 | * amap for the entire stack range we could end up wasting a large |
211 | * amount of allocated KVM. |
212 | * |
213 | * for example, on the i386 at boot time we allocate two amaps for the stack |
214 | * of /sbin/init: |
215 | * 1. a 7680 slot amap at protection 0 (reserve space for stack) |
216 | * 2. a 512 slot amap at protection 7 (top of stack) |
217 | * |
218 | * most of the array allocated for the amaps for this is never used. |
219 | * the amap interface provides a way for us to avoid this problem by |
220 | * allowing amap_copy() to break larger amaps up into smaller sized |
221 | * chunks (controlled by the "canchunk" option). we use this feature |
222 | * to reduce our memory usage with the BSD stack management. if we |
223 | * are asked to create an amap with more than UVM_AMAP_LARGE slots in it, |
224 | * we attempt to break it up into a UVM_AMAP_CHUNK sized amap if the |
225 | * "canchunk" flag is set. |
226 | * |
227 | * so, in the i386 example, the 7680 slot area is never referenced so |
228 | * nothing gets allocated (amap_copy is never called because the protection |
229 | * is zero). the 512 slot area for the top of the stack is referenced. |
230 | * the chunking code breaks it up into 16 slot chunks (hopefully a single |
231 | * 16 slot chunk is enough to handle the whole stack). |
232 | */ |
233 | |
234 | #define UVM_AMAP_LARGE 256 /* # of slots in "large" amap */ |
235 | #define UVM_AMAP_CHUNK 16 /* # of slots to chunk large amaps in */ |
236 | |
237 | #ifdef _KERNEL |
238 | |
239 | /* |
240 | * macros |
241 | */ |
242 | |
243 | /* AMAP_B2SLOT: convert byte offset to slot */ |
244 | #define AMAP_B2SLOT(S,B) { \ |
245 | KASSERT(((B) & (PAGE_SIZE - 1)) == 0); \ |
246 | (S) = (B) >> PAGE_SHIFT; \ |
247 | } |
248 | |
249 | /* |
250 | * lock/unlock/refs/flags macros |
251 | */ |
252 | |
253 | #define amap_flags(AMAP) ((AMAP)->am_flags) |
254 | #define amap_lock(AMAP) mutex_enter((AMAP)->am_lock) |
255 | #define amap_lock_try(AMAP) mutex_tryenter((AMAP)->am_lock) |
256 | #define amap_refs(AMAP) ((AMAP)->am_ref) |
257 | #define amap_unlock(AMAP) mutex_exit((AMAP)->am_lock) |
258 | |
259 | /* |
260 | * if we enable PPREF, then we have a couple of extra functions that |
261 | * we need to prototype here... |
262 | */ |
263 | |
264 | #ifdef UVM_AMAP_PPREF |
265 | |
266 | #define PPREF_NONE ((int *) -1) /* not using ppref */ |
267 | |
268 | void amap_pp_adjref /* adjust references */ |
269 | (struct vm_amap *, int, vsize_t, int, |
270 | struct vm_anon **); |
271 | void amap_pp_establish /* establish ppref */ |
272 | (struct vm_amap *, vaddr_t); |
273 | void amap_wiperange /* wipe part of an amap */ |
274 | (struct vm_amap *, int, int, struct vm_anon **); |
275 | #endif /* UVM_AMAP_PPREF */ |
276 | |
277 | #endif /* _KERNEL */ |
278 | |
279 | #endif /* _UVM_UVM_AMAP_H_ */ |
280 | |