1 /* $NetBSD: uvm_amap.h,v 1.33 2007/07/21 19:21:53 ad Exp $ */ 2 3 /* 4 * 5 * Copyright (c) 1997 Charles D. Cranor and Washington University. 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by Charles D. Cranor and 19 * Washington University. 20 * 4. The name of the author may not be used to endorse or promote products 21 * derived from this software without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 24 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 25 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 26 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 27 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 28 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 29 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 30 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 31 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 32 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 33 */ 34 35 #ifndef _UVM_UVM_AMAP_H_ 36 #define _UVM_UVM_AMAP_H_ 37 38 /* 39 * uvm_amap.h: general amap interface and amap implementation-specific info 40 */ 41 42 /* 43 * an amap structure contains pointers to a set of anons that are 44 * mapped together in virtual memory (an anon is a single page of 45 * anonymous virtual memory -- see uvm_anon.h). in uvm we hide the 46 * details of the implementation of amaps behind a general amap 47 * interface. this allows us to change the amap implementation 48 * without having to touch the rest of the code. this file is divided 49 * into two parts: the definition of the uvm amap interface and the 50 * amap implementation-specific definitions. 51 */ 52 53 #ifdef _KERNEL 54 55 /* 56 * part 1: amap interface 57 */ 58 59 void uvm_amap_init(void); 60 61 /* 62 * forward definition of vm_amap structure. only amap 63 * implementation-specific code should directly access the fields of 64 * this structure. 65 */ 66 67 struct vm_amap; 68 69 70 /* 71 * prototypes for the amap interface 72 */ 73 74 void amap_add /* add an anon to an amap */ 75 (struct vm_aref *, vaddr_t, 76 struct vm_anon *, bool); 77 struct vm_amap *amap_alloc /* allocate a new amap */ 78 (vaddr_t, vaddr_t, int); 79 void amap_copy /* clear amap needs-copy flag */ 80 (struct vm_map *, struct vm_map_entry *, int, 81 vaddr_t, vaddr_t); 82 void amap_cow_now /* resolve all COW faults now */ 83 (struct vm_map *, struct vm_map_entry *); 84 int amap_extend /* make amap larger */ 85 (struct vm_map_entry *, vsize_t, int); 86 int amap_flags /* get amap's flags */ 87 (struct vm_amap *); 88 void amap_free /* free amap */ 89 (struct vm_amap *); 90 void amap_lock /* lock amap */ 91 (struct vm_amap *); 92 struct vm_anon *amap_lookup /* lookup an anon @ offset in amap */ 93 (struct vm_aref *, vaddr_t); 94 void amap_lookups /* lookup multiple anons */ 95 (struct vm_aref *, vaddr_t, 96 struct vm_anon **, int); 97 void amap_ref /* add a reference to an amap */ 98 (struct vm_amap *, vaddr_t, vsize_t, int); 99 int amap_refs /* get number of references of amap */ 100 (struct vm_amap *); 101 void amap_share_protect /* protect pages in a shared amap */ 102 (struct vm_map_entry *, vm_prot_t); 103 void amap_splitref /* split reference to amap into two */ 104 (struct vm_aref *, struct vm_aref *, vaddr_t); 105 void amap_unadd /* remove an anon from an amap */ 106 (struct vm_aref *, vaddr_t); 107 void amap_unlock /* unlock amap */ 108 (struct vm_amap *); 109 void amap_unref /* drop reference to an amap */ 110 (struct vm_amap *, vaddr_t, vsize_t, bool); 111 void amap_wipeout /* remove all anons from amap */ 112 (struct vm_amap *); 113 bool amap_swap_off 114 (int, int); 115 116 /* 117 * amap flag values 118 */ 119 120 #define AMAP_SHARED 0x1 /* amap is shared */ 121 #define AMAP_REFALL 0x2 /* amap_ref: reference entire amap */ 122 #define AMAP_SWAPOFF 0x4 /* amap_swap_off() is in progress */ 123 124 /* 125 * amap_copy flags 126 */ 127 128 #define AMAP_COPY_NOWAIT 0x02 /* not allowed to sleep */ 129 #define AMAP_COPY_NOCHUNK 0x04 /* not allowed to chunk */ 130 #define AMAP_COPY_NOMERGE 0x08 /* not allowed to merge */ 131 132 /* 133 * amap_extend flags 134 */ 135 #define AMAP_EXTEND_BACKWARDS 0x00 /* add "size" to start of map */ 136 #define AMAP_EXTEND_FORWARDS 0x01 /* add "size" to end of map */ 137 #define AMAP_EXTEND_NOWAIT 0x02 /* not allowed to sleep */ 138 139 #endif /* _KERNEL */ 140 141 /**********************************************************************/ 142 143 /* 144 * part 2: amap implementation-specific info 145 */ 146 147 /* 148 * we currently provide an array-based amap implementation. in this 149 * implementation we provide the option of tracking split references 150 * so that we don't lose track of references during partial unmaps 151 * ... this is enabled with the "UVM_AMAP_PPREF" define. 152 */ 153 154 #define UVM_AMAP_PPREF /* track partial references */ 155 156 /* 157 * here is the definition of the vm_amap structure for this implementation. 158 */ 159 160 struct vm_amap { 161 kmutex_t am_l; /* lock [locks all vm_amap fields] */ 162 int am_ref; /* reference count */ 163 int am_flags; /* flags */ 164 int am_maxslot; /* max # of slots allocated */ 165 int am_nslot; /* # of slots currently in map ( <= maxslot) */ 166 int am_nused; /* # of slots currently in use */ 167 int *am_slots; /* contig array of active slots */ 168 int *am_bckptr; /* back pointer array to am_slots */ 169 struct vm_anon **am_anon; /* array of anonymous pages */ 170 #ifdef UVM_AMAP_PPREF 171 int *am_ppref; /* per page reference count (if !NULL) */ 172 #endif 173 LIST_ENTRY(vm_amap) am_list; 174 }; 175 176 /* 177 * note that am_slots, am_bckptr, and am_anon are arrays. this allows 178 * fast lookup of pages based on their virual address at the expense of 179 * some extra memory. in the future we should be smarter about memory 180 * usage and fall back to a non-array based implementation on systems 181 * that are short of memory (XXXCDC). 182 * 183 * the entries in the array are called slots... for example an amap that 184 * covers four pages of virtual memory is said to have four slots. here 185 * is an example of the array usage for a four slot amap. note that only 186 * slots one and three have anons assigned to them. "D/C" means that we 187 * "don't care" about the value. 188 * 189 * 0 1 2 3 190 * am_anon: NULL, anon0, NULL, anon1 (actual pointers to anons) 191 * am_bckptr: D/C, 1, D/C, 0 (points to am_slots entry) 192 * 193 * am_slots: 3, 1, D/C, D/C (says slots 3 and 1 are in use) 194 * 195 * note that am_bckptr is D/C if the slot in am_anon is set to NULL. 196 * to find the entry in am_slots for an anon, look at am_bckptr[slot], 197 * thus the entry for slot 3 in am_slots[] is at am_slots[am_bckptr[3]]. 198 * in general, if am_anon[X] is non-NULL, then the following must be 199 * true: am_slots[am_bckptr[X]] == X 200 * 201 * note that am_slots is always contig-packed. 202 */ 203 204 /* 205 * defines for handling of large sparce amaps: 206 * 207 * one of the problems of array-based amaps is that if you allocate a 208 * large sparcely-used area of virtual memory you end up allocating 209 * large arrays that, for the most part, don't get used. this is a 210 * problem for BSD in that the kernel likes to make these types of 211 * allocations to "reserve" memory for possible future use. 212 * 213 * for example, the kernel allocates (reserves) a large chunk of user 214 * VM for possible stack growth. most of the time only a page or two 215 * of this VM is actually used. since the stack is anonymous memory 216 * it makes sense for it to live in an amap, but if we allocated an 217 * amap for the entire stack range we could end up wasting a large 218 * amount of malloc'd KVM. 219 * 220 * for example, on the i386 at boot time we allocate two amaps for the stack 221 * of /sbin/init: 222 * 1. a 7680 slot amap at protection 0 (reserve space for stack) 223 * 2. a 512 slot amap at protection 7 (top of stack) 224 * 225 * most of the array allocated for the amaps for this is never used. 226 * the amap interface provides a way for us to avoid this problem by 227 * allowing amap_copy() to break larger amaps up into smaller sized 228 * chunks (controlled by the "canchunk" option). we use this feature 229 * to reduce our memory usage with the BSD stack management. if we 230 * are asked to create an amap with more than UVM_AMAP_LARGE slots in it, 231 * we attempt to break it up into a UVM_AMAP_CHUNK sized amap if the 232 * "canchunk" flag is set. 233 * 234 * so, in the i386 example, the 7680 slot area is never referenced so 235 * nothing gets allocated (amap_copy is never called because the protection 236 * is zero). the 512 slot area for the top of the stack is referenced. 237 * the chunking code breaks it up into 16 slot chunks (hopefully a single 238 * 16 slot chunk is enough to handle the whole stack). 239 */ 240 241 #define UVM_AMAP_LARGE 256 /* # of slots in "large" amap */ 242 #define UVM_AMAP_CHUNK 16 /* # of slots to chunk large amaps in */ 243 244 #ifdef _KERNEL 245 246 /* 247 * macros 248 */ 249 250 /* AMAP_B2SLOT: convert byte offset to slot */ 251 #define AMAP_B2SLOT(S,B) { \ 252 KASSERT(((B) & (PAGE_SIZE - 1)) == 0); \ 253 (S) = (B) >> PAGE_SHIFT; \ 254 } 255 256 /* 257 * lock/unlock/refs/flags macros 258 */ 259 260 #define amap_flags(AMAP) ((AMAP)->am_flags) 261 #define amap_lock(AMAP) mutex_enter(&(AMAP)->am_l) 262 #define amap_lock_try(AMAP) mutex_tryenter(&(AMAP)->am_l) 263 #define amap_refs(AMAP) ((AMAP)->am_ref) 264 #define amap_unlock(AMAP) mutex_exit(&(AMAP)->am_l) 265 266 /* 267 * if we enable PPREF, then we have a couple of extra functions that 268 * we need to prototype here... 269 */ 270 271 #ifdef UVM_AMAP_PPREF 272 273 #define PPREF_NONE ((int *) -1) /* not using ppref */ 274 275 void amap_pp_adjref /* adjust references */ 276 (struct vm_amap *, int, vsize_t, int); 277 void amap_pp_establish /* establish ppref */ 278 (struct vm_amap *, vaddr_t); 279 void amap_wiperange /* wipe part of an amap */ 280 (struct vm_amap *, int, int); 281 #endif /* UVM_AMAP_PPREF */ 282 283 #endif /* _KERNEL */ 284 285 #endif /* _UVM_UVM_AMAP_H_ */ 286