phys_pager.c

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    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: releng/12.0/sys/vm/phys_pager.c 326272 2017-11-27 15:23:17Z pfg $");
   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 };
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FreeBSD/Linux Kernel Cross Reference sys/vm/phys_pager.c

FreeBSD/Linux Kernel Cross Reference
sys/vm/phys_pager.c
