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("$FreeBSD$");
   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 int default_phys_pager_getpages(vm_object_t object, vm_page_t *m,
   55     int count, int *rbehind, int *rahead);
   56 static int default_phys_pager_populate(vm_object_t object, vm_pindex_t pidx,
   57     int fault_type, vm_prot_t max_prot, vm_pindex_t *first, vm_pindex_t *last);
   58 static boolean_t default_phys_pager_haspage(vm_object_t object,
   59     vm_pindex_t pindex, int *before, int *after);
   60 struct phys_pager_ops default_phys_pg_ops = {
   61         .phys_pg_getpages = default_phys_pager_getpages,
   62         .phys_pg_populate = default_phys_pager_populate,
   63         .phys_pg_haspage = default_phys_pager_haspage,
   64         .phys_pg_ctor = NULL,
   65         .phys_pg_dtor = NULL,
   66 };
   67 
   68 static void
   69 phys_pager_init(void)
   70 {
   71 
   72         TAILQ_INIT(&phys_pager_object_list);
   73         mtx_init(&phys_pager_mtx, "phys_pager list", NULL, MTX_DEF);
   74 }
   75 
   76 vm_object_t
   77 phys_pager_allocate(void *handle, struct phys_pager_ops *ops, void *data,
   78     vm_ooffset_t size, vm_prot_t prot, vm_ooffset_t foff, struct ucred *cred)
   79 {
   80         vm_object_t object, object1;
   81         vm_pindex_t pindex;
   82         bool init;
   83 
   84         /*
   85          * Offset should be page aligned.
   86          */
   87         if (foff & PAGE_MASK)
   88                 return (NULL);
   89 
   90         pindex = OFF_TO_IDX(foff + PAGE_MASK + size);
   91         init = true;
   92 
   93         if (handle != NULL) {
   94                 mtx_lock(&phys_pager_mtx);
   95                 /*
   96                  * Look up pager, creating as necessary.
   97                  */
   98                 object1 = NULL;
   99                 object = vm_pager_object_lookup(&phys_pager_object_list, handle);
  100                 if (object == NULL) {
  101                         /*
  102                          * Allocate object and associate it with the pager.
  103                          */
  104                         mtx_unlock(&phys_pager_mtx);
  105                         object1 = vm_object_allocate(OBJT_PHYS, pindex);
  106                         mtx_lock(&phys_pager_mtx);
  107                         object = vm_pager_object_lookup(&phys_pager_object_list,
  108                             handle);
  109                         if (object != NULL) {
  110                                 /*
  111                                  * We raced with other thread while
  112                                  * allocating object.
  113                                  */
  114                                 if (pindex > object->size)
  115                                         object->size = pindex;
  116                                 init = false;
  117                         } else {
  118                                 object = object1;
  119                                 object1 = NULL;
  120                                 object->handle = handle;
  121                                 object->un_pager.phys.ops = ops;
  122                                 object->un_pager.phys.data_ptr = data;
  123                                 if (ops->phys_pg_populate != NULL)
  124                                         vm_object_set_flag(object, OBJ_POPULATE);
  125                                 TAILQ_INSERT_TAIL(&phys_pager_object_list,
  126                                     object, pager_object_list);
  127                         }
  128                 } else {
  129                         if (pindex > object->size)
  130                                 object->size = pindex;
  131                 }
  132                 mtx_unlock(&phys_pager_mtx);
  133                 vm_object_deallocate(object1);
  134         } else {
  135                 object = vm_object_allocate(OBJT_PHYS, pindex);
  136                 object->un_pager.phys.ops = ops;
  137                 object->un_pager.phys.data_ptr = data;
  138                 if (ops->phys_pg_populate != NULL)
  139                         vm_object_set_flag(object, OBJ_POPULATE);
  140         }
  141         if (init && ops->phys_pg_ctor != NULL)
  142                 ops->phys_pg_ctor(object, prot, foff, cred);
  143 
  144         return (object);
  145 }
  146 
  147 static vm_object_t
  148 phys_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
  149     vm_ooffset_t foff, struct ucred *ucred)
  150 {
  151         return (phys_pager_allocate(handle, &default_phys_pg_ops, NULL,
  152             size, prot, foff, ucred));
  153 }
  154 
  155 static void
  156 phys_pager_dealloc(vm_object_t object)
  157 {
  158 
  159         if (object->handle != NULL) {
  160                 VM_OBJECT_WUNLOCK(object);
  161                 mtx_lock(&phys_pager_mtx);
  162                 TAILQ_REMOVE(&phys_pager_object_list, object, pager_object_list);
  163                 mtx_unlock(&phys_pager_mtx);
  164                 VM_OBJECT_WLOCK(object);
  165         }
  166         object->type = OBJT_DEAD;
  167         if (object->un_pager.phys.ops->phys_pg_dtor != NULL)
  168                 object->un_pager.phys.ops->phys_pg_dtor(object);
  169         object->handle = NULL;
  170 }
  171 
  172 /*
  173  * Fill as many pages as vm_fault has allocated for us.
  174  */
  175 static int
  176 default_phys_pager_getpages(vm_object_t object, vm_page_t *m, int count,
  177     int *rbehind, int *rahead)
  178 {
  179         int i;
  180 
  181         VM_OBJECT_ASSERT_WLOCKED(object);
  182         for (i = 0; i < count; i++) {
  183                 if (m[i]->valid == 0) {
  184                         if ((m[i]->flags & PG_ZERO) == 0)
  185                                 pmap_zero_page(m[i]);
  186                         m[i]->valid = VM_PAGE_BITS_ALL;
  187                 }
  188                 KASSERT(m[i]->valid == VM_PAGE_BITS_ALL,
  189                     ("phys_pager_getpages: partially valid page %p", m[i]));
  190                 KASSERT(m[i]->dirty == 0,
  191                     ("phys_pager_getpages: dirty page %p", m[i]));
  192         }
  193         if (rbehind)
  194                 *rbehind = 0;
  195         if (rahead)
  196                 *rahead = 0;
  197         return (VM_PAGER_OK);
  198 }
  199 
  200 static int
  201 phys_pager_getpages(vm_object_t object, vm_page_t *m, int count, int *rbehind,
  202     int *rahead)
  203 {
  204         return (object->un_pager.phys.ops->phys_pg_getpages(object, m,
  205             count, rbehind, rahead));
  206 }
  207 
  208 /*
  209  * Implement a pretty aggressive clustered getpages strategy.  Hint that
  210  * everything in an entire 4MB window should be prefaulted at once.
  211  *
  212  * 4MB (1024 slots per page table page) is convenient for x86,
  213  * but may not be for other arches.
  214  */
  215 #ifndef PHYSCLUSTER
  216 #define PHYSCLUSTER 1024
  217 #endif
  218 static int phys_pager_cluster = PHYSCLUSTER;
  219 SYSCTL_INT(_vm, OID_AUTO, phys_pager_cluster, CTLFLAG_RWTUN,
  220     &phys_pager_cluster, 0,
  221     "prefault window size for phys pager");
  222 
  223 /*
  224  * Max hint to vm_page_alloc() about the further allocation needs
  225  * inside the phys_pager_populate() loop.  The number of bits used to
  226  * implement VM_ALLOC_COUNT() determines the hard limit on this value.
  227  * That limit is currently 65535.
  228  */
  229 #define PHYSALLOC       16
  230 
  231 static int
  232 default_phys_pager_populate(vm_object_t object, vm_pindex_t pidx,
  233     int fault_type __unused, vm_prot_t max_prot __unused, vm_pindex_t *first,
  234     vm_pindex_t *last)
  235 {
  236         vm_page_t m;
  237         vm_pindex_t base, end, i;
  238         int ahead;
  239 
  240         base = rounddown(pidx, phys_pager_cluster);
  241         end = base + phys_pager_cluster - 1;
  242         if (end >= object->size)
  243                 end = object->size - 1;
  244         if (*first > base)
  245                 base = *first;
  246         if (end > *last)
  247                 end = *last;
  248         *first = base;
  249         *last = end;
  250 
  251         for (i = base; i <= end; i++) {
  252 retry:
  253                 m = vm_page_lookup(object, i);
  254                 if (m == NULL) {
  255                         ahead = MIN(end - i, PHYSALLOC);
  256                         m = vm_page_alloc(object, i, VM_ALLOC_NORMAL |
  257                             VM_ALLOC_ZERO | VM_ALLOC_WAITFAIL |
  258                             VM_ALLOC_COUNT(ahead));
  259                         if (m == NULL)
  260                                 goto retry;
  261                         if ((m->flags & PG_ZERO) == 0)
  262                                 pmap_zero_page(m);
  263                         m->valid = VM_PAGE_BITS_ALL;
  264                 } else if (vm_page_xbusied(m)) {
  265                         vm_page_lock(m);
  266                         VM_OBJECT_WUNLOCK(object);
  267                         vm_page_busy_sleep(m, "physb", true);
  268                         VM_OBJECT_WLOCK(object);
  269                         goto retry;
  270                 } else {
  271                         vm_page_xbusy(m);
  272                         if (m->valid != VM_PAGE_BITS_ALL)
  273                                 vm_page_zero_invalid(m, TRUE);
  274                 }
  275 
  276                 KASSERT(m->valid == VM_PAGE_BITS_ALL,
  277                     ("phys_pager_populate: partially valid page %p", m));
  278                 KASSERT(m->dirty == 0,
  279                     ("phys_pager_populate: dirty page %p", m));
  280         }
  281         return (VM_PAGER_OK);
  282 }
  283 
  284 static int
  285 phys_pager_populate(vm_object_t object, vm_pindex_t pidx, int fault_type,
  286     vm_prot_t max_prot, vm_pindex_t *first, vm_pindex_t *last)
  287 {
  288         return (object->un_pager.phys.ops->phys_pg_populate(object, pidx,
  289             fault_type, max_prot, first, last));
  290 }
  291 
  292 static void
  293 phys_pager_putpages(vm_object_t object, vm_page_t *m, int count, boolean_t sync,
  294     int *rtvals)
  295 {
  296 
  297         panic("phys_pager_putpage called");
  298 }
  299 
  300 static boolean_t
  301 default_phys_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
  302     int *after)
  303 {
  304         vm_pindex_t base, end;
  305 
  306         base = rounddown(pindex, phys_pager_cluster);
  307         end = base + phys_pager_cluster - 1;
  308         if (before != NULL)
  309                 *before = pindex - base;
  310         if (after != NULL)
  311                 *after = end - pindex;
  312         return (TRUE);
  313 }
  314 
  315 static boolean_t
  316 phys_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
  317     int *after)
  318 {
  319         return (object->un_pager.phys.ops->phys_pg_haspage(object, pindex,
  320             before, after));
  321 }
  322 
  323 struct pagerops physpagerops = {
  324         .pgo_init =     phys_pager_init,
  325         .pgo_alloc =    phys_pager_alloc,
  326         .pgo_dealloc =  phys_pager_dealloc,
  327         .pgo_getpages = phys_pager_getpages,
  328         .pgo_putpages = phys_pager_putpages,
  329         .pgo_haspage =  phys_pager_haspage,
  330         .pgo_populate = phys_pager_populate,
  331 };
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FreeBSD/Linux Kernel Cross Reference sys/vm/phys_pager.c

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