sys/vm/phys_pager.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
   3  *
   4  * Copyright (c) 2000 Peter Wemm
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
  16  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  17  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  18  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
  19  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  21  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  22  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  24  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  25  * SUCH DAMAGE.
  26  */
  27
  28 #include <sys/cdefs.h>
  29 __FBSDID("$FreeBSD$");
  30
  31 #include <sys/param.h>
  32 #include <sys/systm.h>
  33 #include <sys/conf.h>
  34 #include <sys/kernel.h>
  35 #include <sys/lock.h>
  36 #include <sys/proc.h>
  37 #include <sys/mutex.h>
  38 #include <sys/mman.h>
  39 #include <sys/rwlock.h>
  40 #include <sys/sysctl.h>
  41
  42 #include <vm/vm.h>
  43 #include <vm/vm_param.h>
  44 #include <vm/vm_object.h>
  45 #include <vm/vm_page.h>
  46 #include <vm/vm_pageout.h>
  47 #include <vm/vm_pager.h>
  48
  49 /* list of phys pager objects */
  50 static struct pagerlst phys_pager_object_list;
  51 /* protect access to phys_pager_object_list */
  52 static struct mtx phys_pager_mtx;
  53
  54 static void
  55 phys_pager_init(void)
  56 {
  57
  58         TAILQ_INIT(&phys_pager_object_list);
  59         mtx_init(&phys_pager_mtx, "phys_pager list", NULL, MTX_DEF);
  60 }
  61
  62 static vm_object_t
  63 phys_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
  64     vm_ooffset_t foff, struct ucred *cred)
  65 {
  66         vm_object_t object, object1;
  67         vm_pindex_t pindex;
  68
  69         /*
  70          * Offset should be page aligned.
  71          */
  72         if (foff & PAGE_MASK)
  73                 return (NULL);
  74
  75         pindex = OFF_TO_IDX(foff + PAGE_MASK + size);
  76
  77         if (handle != NULL) {
  78                 mtx_lock(&phys_pager_mtx);
  79                 /*
  80                  * Look up pager, creating as necessary.
  81                  */
  82                 object1 = NULL;
  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                         mtx_unlock(&phys_pager_mtx);
  89                         object1 = vm_object_allocate(OBJT_PHYS, pindex);
  90                         mtx_lock(&phys_pager_mtx);
  91                         object = vm_pager_object_lookup(&phys_pager_object_list,
  92                             handle);
  93                         if (object != NULL) {
  94                                 /*
  95                                  * We raced with other thread while
  96                                  * allocating object.
  97                                  */
  98                                 if (pindex > object->size)
  99                                         object->size = pindex;
 100                         } else {
 101                                 object = object1;
 102                                 object1 = NULL;
 103                                 object->handle = handle;
 104                                 vm_object_set_flag(object, OBJ_POPULATE);
 105                                 TAILQ_INSERT_TAIL(&phys_pager_object_list,
 106                                     object, pager_object_list);
 107                         }
 108                 } else {
 109                         if (pindex > object->size)
 110                                 object->size = pindex;
 111                 }
 112                 mtx_unlock(&phys_pager_mtx);
 113                 vm_object_deallocate(object1);
 114         } else {
 115                 object = vm_object_allocate(OBJT_PHYS, pindex);
 116                 vm_object_set_flag(object, OBJ_POPULATE);
 117         }
 118
 119         return (object);
 120 }
 121
 122 static void
 123 phys_pager_dealloc(vm_object_t object)
 124 {
 125
 126         if (object->handle != NULL) {
 127                 VM_OBJECT_WUNLOCK(object);
 128                 mtx_lock(&phys_pager_mtx);
 129                 TAILQ_REMOVE(&phys_pager_object_list, object, pager_object_list);
 130                 mtx_unlock(&phys_pager_mtx);
 131                 VM_OBJECT_WLOCK(object);
 132         }
 133         object->handle = NULL;
 134         object->type = OBJT_DEAD;
 135 }
 136
 137 /*
 138  * Fill as many pages as vm_fault has allocated for us.
 139  */
 140 static int
 141 phys_pager_getpages(vm_object_t object, vm_page_t *m, int count, int *rbehind,
 142     int *rahead)
 143 {
 144         int i;
 145
 146         VM_OBJECT_ASSERT_WLOCKED(object);
 147         for (i = 0; i < count; i++) {
 148                 if (m[i]->valid == 0) {
 149                         if ((m[i]->flags & PG_ZERO) == 0)
 150                                 pmap_zero_page(m[i]);
 151                         m[i]->valid = VM_PAGE_BITS_ALL;
 152                 }
 153                 KASSERT(m[i]->valid == VM_PAGE_BITS_ALL,
 154                     ("phys_pager_getpages: partially valid page %p", m[i]));
 155                 KASSERT(m[i]->dirty == 0,
 156                     ("phys_pager_getpages: dirty page %p", m[i]));
 157         }
 158         if (rbehind)
 159                 *rbehind = 0;
 160         if (rahead)
 161                 *rahead = 0;
 162         return (VM_PAGER_OK);
 163 }
 164
 165 /*
 166  * Implement a pretty aggressive clustered getpages strategy.  Hint that
 167  * everything in an entire 4MB window should be prefaulted at once.
 168  *
 169  * 4MB (1024 slots per page table page) is convenient for x86,
 170  * but may not be for other arches.
 171  */
 172 #ifndef PHYSCLUSTER
 173 #define PHYSCLUSTER 1024
 174 #endif
 175 static int phys_pager_cluster = PHYSCLUSTER;
 176 SYSCTL_INT(_vm, OID_AUTO, phys_pager_cluster, CTLFLAG_RWTUN,
 177     &phys_pager_cluster, 0,
 178     "prefault window size for phys pager");
 179
 180 /*
 181  * Max hint to vm_page_alloc() about the further allocation needs
 182  * inside the phys_pager_populate() loop.  The number of bits used to
 183  * implement VM_ALLOC_COUNT() determines the hard limit on this value.
 184  * That limit is currently 65535.
 185  */
 186 #define PHYSALLOC       16
 187
 188 static int
 189 phys_pager_populate(vm_object_t object, vm_pindex_t pidx,
 190     int fault_type __unused, vm_prot_t max_prot __unused, vm_pindex_t *first,
 191     vm_pindex_t *last)
 192 {
 193         vm_page_t m;
 194         vm_pindex_t base, end, i;
 195         int ahead;
 196
 197         base = rounddown(pidx, phys_pager_cluster);
 198         end = base + phys_pager_cluster - 1;
 199         if (end >= object->size)
 200                 end = object->size - 1;
 201         if (*first > base)
 202                 base = *first;
 203         if (end > *last)
 204                 end = *last;
 205         *first = base;
 206         *last = end;
 207
 208         for (i = base; i <= end; i++) {
 209 retry:
 210                 m = vm_page_lookup(object, i);
 211                 if (m == NULL) {
 212                         ahead = MIN(end - i, PHYSALLOC);
 213                         m = vm_page_alloc(object, i, VM_ALLOC_NORMAL |
 214                             VM_ALLOC_ZERO | VM_ALLOC_WAITFAIL |
 215                             VM_ALLOC_COUNT(ahead));
 216                         if (m == NULL)
 217                                 goto retry;
 218                         if ((m->flags & PG_ZERO) == 0)
 219                                 pmap_zero_page(m);
 220                         m->valid = VM_PAGE_BITS_ALL;
 221                 } else if (vm_page_xbusied(m)) {
 222                         vm_page_lock(m);
 223                         VM_OBJECT_WUNLOCK(object);
 224                         vm_page_busy_sleep(m, "physb", true);
 225                         VM_OBJECT_WLOCK(object);
 226                         goto retry;
 227                 } else {
 228                         vm_page_xbusy(m);
 229                         if (m->valid != VM_PAGE_BITS_ALL)
 230                                 vm_page_zero_invalid(m, TRUE);
 231                 }
 232
 233                 KASSERT(m->valid == VM_PAGE_BITS_ALL,
 234                     ("phys_pager_populate: partially valid page %p", m));
 235                 KASSERT(m->dirty == 0,
 236                     ("phys_pager_populate: dirty page %p", m));
 237         }
 238         return (VM_PAGER_OK);
 239 }
 240
 241 static void
 242 phys_pager_putpages(vm_object_t object, vm_page_t *m, int count, boolean_t sync,
 243     int *rtvals)
 244 {
 245
 246         panic("phys_pager_putpage called");
 247 }
 248
 249 static boolean_t
 250 phys_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
 251     int *after)
 252 {
 253         vm_pindex_t base, end;
 254
 255         base = rounddown(pindex, phys_pager_cluster);
 256         end = base + phys_pager_cluster - 1;
 257         if (before != NULL)
 258                 *before = pindex - base;
 259         if (after != NULL)
 260                 *after = end - pindex;
 261         return (TRUE);
 262 }
 263
 264 struct pagerops physpagerops = {
 265         .pgo_init =     phys_pager_init,
 266         .pgo_alloc =    phys_pager_alloc,
 267         .pgo_dealloc =  phys_pager_dealloc,
 268         .pgo_getpages = phys_pager_getpages,
 269         .pgo_putpages = phys_pager_putpages,
 270         .pgo_haspage =  phys_pager_haspage,
 271         .pgo_populate = phys_pager_populate,
 272 };