The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/vm/vm_kern.c

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    1 /*-
    2  * Copyright (c) 1991, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * This code is derived from software contributed to Berkeley by
    6  * The Mach Operating System project at Carnegie-Mellon University.
    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  * 4. Neither the name of the University nor the names of its contributors
   17  *    may be used to endorse or promote products derived from this software
   18  *    without specific prior written permission.
   19  *
   20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   30  * SUCH DAMAGE.
   31  *
   32  *      from: @(#)vm_kern.c     8.3 (Berkeley) 1/12/94
   33  *
   34  *
   35  * Copyright (c) 1987, 1990 Carnegie-Mellon University.
   36  * All rights reserved.
   37  *
   38  * Authors: Avadis Tevanian, Jr., Michael Wayne Young
   39  *
   40  * Permission to use, copy, modify and distribute this software and
   41  * its documentation is hereby granted, provided that both the copyright
   42  * notice and this permission notice appear in all copies of the
   43  * software, derivative works or modified versions, and any portions
   44  * thereof, and that both notices appear in supporting documentation.
   45  *
   46  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
   47  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
   48  * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
   49  *
   50  * Carnegie Mellon requests users of this software to return to
   51  *
   52  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
   53  *  School of Computer Science
   54  *  Carnegie Mellon University
   55  *  Pittsburgh PA 15213-3890
   56  *
   57  * any improvements or extensions that they make and grant Carnegie the
   58  * rights to redistribute these changes.
   59  */
   60 
   61 /*
   62  *      Kernel memory management.
   63  */
   64 
   65 #include <sys/cdefs.h>
   66 __FBSDID("$FreeBSD: releng/8.2/sys/vm/vm_kern.c 215938 2010-11-27 12:26:40Z jchandra $");
   67 
   68 #include <sys/param.h>
   69 #include <sys/systm.h>
   70 #include <sys/kernel.h>         /* for ticks and hz */
   71 #include <sys/eventhandler.h>
   72 #include <sys/lock.h>
   73 #include <sys/mutex.h>
   74 #include <sys/proc.h>
   75 #include <sys/malloc.h>
   76 #include <sys/sysctl.h>
   77 
   78 #include <vm/vm.h>
   79 #include <vm/vm_param.h>
   80 #include <vm/pmap.h>
   81 #include <vm/vm_map.h>
   82 #include <vm/vm_object.h>
   83 #include <vm/vm_page.h>
   84 #include <vm/vm_pageout.h>
   85 #include <vm/vm_extern.h>
   86 #include <vm/uma.h>
   87 
   88 vm_map_t kernel_map=0;
   89 vm_map_t kmem_map=0;
   90 vm_map_t exec_map=0;
   91 vm_map_t pipe_map;
   92 vm_map_t buffer_map=0;
   93 
   94 /*
   95  *      kmem_alloc_nofault:
   96  *
   97  *      Allocate a virtual address range with no underlying object and
   98  *      no initial mapping to physical memory.  Any mapping from this
   99  *      range to physical memory must be explicitly created prior to
  100  *      its use, typically with pmap_qenter().  Any attempt to create
  101  *      a mapping on demand through vm_fault() will result in a panic. 
  102  */
  103 vm_offset_t
  104 kmem_alloc_nofault(map, size)
  105         vm_map_t map;
  106         vm_size_t size;
  107 {
  108         vm_offset_t addr;
  109         int result;
  110 
  111         size = round_page(size);
  112         addr = vm_map_min(map);
  113         result = vm_map_find(map, NULL, 0, &addr, size, VMFS_ANY_SPACE,
  114             VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
  115         if (result != KERN_SUCCESS) {
  116                 return (0);
  117         }
  118         return (addr);
  119 }
  120 
  121 /*
  122  *      kmem_alloc_nofault_space:
  123  *
  124  *      Allocate a virtual address range with no underlying object and
  125  *      no initial mapping to physical memory within the specified
  126  *      address space.  Any mapping from this range to physical memory
  127  *      must be explicitly created prior to its use, typically with
  128  *      pmap_qenter().  Any attempt to create a mapping on demand
  129  *      through vm_fault() will result in a panic. 
  130  */
  131 vm_offset_t
  132 kmem_alloc_nofault_space(map, size, find_space)
  133         vm_map_t map;
  134         vm_size_t size;
  135         int find_space;
  136 {
  137         vm_offset_t addr;
  138         int result;
  139 
  140         size = round_page(size);
  141         addr = vm_map_min(map);
  142         result = vm_map_find(map, NULL, 0, &addr, size, find_space,
  143             VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
  144         if (result != KERN_SUCCESS) {
  145                 return (0);
  146         }
  147         return (addr);
  148 }
  149 
  150 /*
  151  *      Allocate wired-down memory in the kernel's address map
  152  *      or a submap.
  153  */
  154 vm_offset_t
  155 kmem_alloc(map, size)
  156         vm_map_t map;
  157         vm_size_t size;
  158 {
  159         vm_offset_t addr;
  160         vm_offset_t offset;
  161         vm_offset_t i;
  162 
  163         size = round_page(size);
  164 
  165         /*
  166          * Use the kernel object for wired-down kernel pages. Assume that no
  167          * region of the kernel object is referenced more than once.
  168          */
  169 
  170         /*
  171          * Locate sufficient space in the map.  This will give us the final
  172          * virtual address for the new memory, and thus will tell us the
  173          * offset within the kernel map.
  174          */
  175         vm_map_lock(map);
  176         if (vm_map_findspace(map, vm_map_min(map), size, &addr)) {
  177                 vm_map_unlock(map);
  178                 return (0);
  179         }
  180         offset = addr - VM_MIN_KERNEL_ADDRESS;
  181         vm_object_reference(kernel_object);
  182         vm_map_insert(map, kernel_object, offset, addr, addr + size,
  183                 VM_PROT_ALL, VM_PROT_ALL, 0);
  184         vm_map_unlock(map);
  185 
  186         /*
  187          * Guarantee that there are pages already in this object before
  188          * calling vm_map_wire.  This is to prevent the following
  189          * scenario:
  190          *
  191          * 1) Threads have swapped out, so that there is a pager for the
  192          * kernel_object. 2) The kmsg zone is empty, and so we are
  193          * kmem_allocing a new page for it. 3) vm_map_wire calls vm_fault;
  194          * there is no page, but there is a pager, so we call
  195          * pager_data_request.  But the kmsg zone is empty, so we must
  196          * kmem_alloc. 4) goto 1 5) Even if the kmsg zone is not empty: when
  197          * we get the data back from the pager, it will be (very stale)
  198          * non-zero data.  kmem_alloc is defined to return zero-filled memory.
  199          *
  200          * We're intentionally not activating the pages we allocate to prevent a
  201          * race with page-out.  vm_map_wire will wire the pages.
  202          */
  203         VM_OBJECT_LOCK(kernel_object);
  204         for (i = 0; i < size; i += PAGE_SIZE) {
  205                 vm_page_t mem;
  206 
  207                 mem = vm_page_grab(kernel_object, OFF_TO_IDX(offset + i),
  208                     VM_ALLOC_NOBUSY | VM_ALLOC_ZERO | VM_ALLOC_RETRY);
  209                 mem->valid = VM_PAGE_BITS_ALL;
  210                 KASSERT((mem->flags & PG_UNMANAGED) != 0,
  211                     ("kmem_alloc: page %p is managed", mem));
  212         }
  213         VM_OBJECT_UNLOCK(kernel_object);
  214 
  215         /*
  216          * And finally, mark the data as non-pageable.
  217          */
  218         (void) vm_map_wire(map, addr, addr + size,
  219             VM_MAP_WIRE_SYSTEM|VM_MAP_WIRE_NOHOLES);
  220 
  221         return (addr);
  222 }
  223 
  224 /*
  225  *      kmem_free:
  226  *
  227  *      Release a region of kernel virtual memory allocated
  228  *      with kmem_alloc, and return the physical pages
  229  *      associated with that region.
  230  *
  231  *      This routine may not block on kernel maps.
  232  */
  233 void
  234 kmem_free(map, addr, size)
  235         vm_map_t map;
  236         vm_offset_t addr;
  237         vm_size_t size;
  238 {
  239 
  240         (void) vm_map_remove(map, trunc_page(addr), round_page(addr + size));
  241 }
  242 
  243 /*
  244  *      kmem_suballoc:
  245  *
  246  *      Allocates a map to manage a subrange
  247  *      of the kernel virtual address space.
  248  *
  249  *      Arguments are as follows:
  250  *
  251  *      parent          Map to take range from
  252  *      min, max        Returned endpoints of map
  253  *      size            Size of range to find
  254  *      superpage_align Request that min is superpage aligned
  255  */
  256 vm_map_t
  257 kmem_suballoc(vm_map_t parent, vm_offset_t *min, vm_offset_t *max,
  258     vm_size_t size, boolean_t superpage_align)
  259 {
  260         int ret;
  261         vm_map_t result;
  262 
  263         size = round_page(size);
  264 
  265         *min = vm_map_min(parent);
  266         ret = vm_map_find(parent, NULL, 0, min, size, superpage_align ?
  267             VMFS_ALIGNED_SPACE : VMFS_ANY_SPACE, VM_PROT_ALL, VM_PROT_ALL,
  268             MAP_ACC_NO_CHARGE);
  269         if (ret != KERN_SUCCESS)
  270                 panic("kmem_suballoc: bad status return of %d", ret);
  271         *max = *min + size;
  272         result = vm_map_create(vm_map_pmap(parent), *min, *max);
  273         if (result == NULL)
  274                 panic("kmem_suballoc: cannot create submap");
  275         if (vm_map_submap(parent, *min, *max, result) != KERN_SUCCESS)
  276                 panic("kmem_suballoc: unable to change range to submap");
  277         return (result);
  278 }
  279 
  280 /*
  281  *      kmem_malloc:
  282  *
  283  *      Allocate wired-down memory in the kernel's address map for the higher
  284  *      level kernel memory allocator (kern/kern_malloc.c).  We cannot use
  285  *      kmem_alloc() because we may need to allocate memory at interrupt
  286  *      level where we cannot block (canwait == FALSE).
  287  *
  288  *      This routine has its own private kernel submap (kmem_map) and object
  289  *      (kmem_object).  This, combined with the fact that only malloc uses
  290  *      this routine, ensures that we will never block in map or object waits.
  291  *
  292  *      We don't worry about expanding the map (adding entries) since entries
  293  *      for wired maps are statically allocated.
  294  *
  295  *      `map' is ONLY allowed to be kmem_map or one of the mbuf submaps to
  296  *      which we never free.
  297  */
  298 vm_offset_t
  299 kmem_malloc(map, size, flags)
  300         vm_map_t map;
  301         vm_size_t size;
  302         int flags;
  303 {
  304         vm_offset_t addr;
  305         int i, rv;
  306 
  307         size = round_page(size);
  308         addr = vm_map_min(map);
  309 
  310         /*
  311          * Locate sufficient space in the map.  This will give us the final
  312          * virtual address for the new memory, and thus will tell us the
  313          * offset within the kernel map.
  314          */
  315         vm_map_lock(map);
  316         if (vm_map_findspace(map, vm_map_min(map), size, &addr)) {
  317                 vm_map_unlock(map);
  318                 if ((flags & M_NOWAIT) == 0) {
  319                         for (i = 0; i < 8; i++) {
  320                                 EVENTHANDLER_INVOKE(vm_lowmem, 0);
  321                                 uma_reclaim();
  322                                 vm_map_lock(map);
  323                                 if (vm_map_findspace(map, vm_map_min(map),
  324                                     size, &addr) == 0) {
  325                                         break;
  326                                 }
  327                                 vm_map_unlock(map);
  328                                 tsleep(&i, 0, "nokva", (hz / 4) * (i + 1));
  329                         }
  330                         if (i == 8) {
  331                                 panic("kmem_malloc(%ld): kmem_map too small: %ld total allocated",
  332                                     (long)size, (long)map->size);
  333                         }
  334                 } else {
  335                         return (0);
  336                 }
  337         }
  338 
  339         rv = kmem_back(map, addr, size, flags);
  340         vm_map_unlock(map);
  341         return (rv == KERN_SUCCESS ? addr : 0);
  342 }
  343 
  344 /*
  345  *      kmem_back:
  346  *
  347  *      Allocate physical pages for the specified virtual address range.
  348  */
  349 int
  350 kmem_back(vm_map_t map, vm_offset_t addr, vm_size_t size, int flags)
  351 {
  352         vm_offset_t offset, i;
  353         vm_map_entry_t entry;
  354         vm_page_t m;
  355         int pflags;
  356 
  357         /*
  358          * XXX the map must be locked for write on entry, but there's
  359          * no easy way to assert that.
  360          */
  361 
  362         offset = addr - VM_MIN_KERNEL_ADDRESS;
  363         vm_object_reference(kmem_object);
  364         vm_map_insert(map, kmem_object, offset, addr, addr + size,
  365                 VM_PROT_ALL, VM_PROT_ALL, 0);
  366 
  367         if ((flags & (M_NOWAIT|M_USE_RESERVE)) == M_NOWAIT)
  368                 pflags = VM_ALLOC_INTERRUPT | VM_ALLOC_WIRED;
  369         else
  370                 pflags = VM_ALLOC_SYSTEM | VM_ALLOC_WIRED;
  371 
  372         if (flags & M_ZERO)
  373                 pflags |= VM_ALLOC_ZERO;
  374 
  375         VM_OBJECT_LOCK(kmem_object);
  376         for (i = 0; i < size; i += PAGE_SIZE) {
  377 retry:
  378                 m = vm_page_alloc(kmem_object, OFF_TO_IDX(offset + i), pflags);
  379 
  380                 /*
  381                  * Ran out of space, free everything up and return. Don't need
  382                  * to lock page queues here as we know that the pages we got
  383                  * aren't on any queues.
  384                  */
  385                 if (m == NULL) {
  386                         if ((flags & M_NOWAIT) == 0) {
  387                                 VM_OBJECT_UNLOCK(kmem_object);
  388                                 vm_map_unlock(map);
  389                                 VM_WAIT;
  390                                 vm_map_lock(map);
  391                                 VM_OBJECT_LOCK(kmem_object);
  392                                 goto retry;
  393                         }
  394                         /* 
  395                          * Free the pages before removing the map entry.
  396                          * They are already marked busy.  Calling
  397                          * vm_map_delete before the pages has been freed or
  398                          * unbusied will cause a deadlock.
  399                          */
  400                         while (i != 0) {
  401                                 i -= PAGE_SIZE;
  402                                 m = vm_page_lookup(kmem_object,
  403                                                    OFF_TO_IDX(offset + i));
  404                                 vm_page_lock_queues();
  405                                 vm_page_unwire(m, 0);
  406                                 vm_page_free(m);
  407                                 vm_page_unlock_queues();
  408                         }
  409                         VM_OBJECT_UNLOCK(kmem_object);
  410                         vm_map_delete(map, addr, addr + size);
  411                         return (KERN_NO_SPACE);
  412                 }
  413                 if (flags & M_ZERO && (m->flags & PG_ZERO) == 0)
  414                         pmap_zero_page(m);
  415                 m->valid = VM_PAGE_BITS_ALL;
  416                 KASSERT((m->flags & PG_UNMANAGED) != 0,
  417                     ("kmem_malloc: page %p is managed", m));
  418         }
  419         VM_OBJECT_UNLOCK(kmem_object);
  420 
  421         /*
  422          * Mark map entry as non-pageable. Assert: vm_map_insert() will never
  423          * be able to extend the previous entry so there will be a new entry
  424          * exactly corresponding to this address range and it will have
  425          * wired_count == 0.
  426          */
  427         if (!vm_map_lookup_entry(map, addr, &entry) ||
  428             entry->start != addr || entry->end != addr + size ||
  429             entry->wired_count != 0)
  430                 panic("kmem_malloc: entry not found or misaligned");
  431         entry->wired_count = 1;
  432 
  433         /*
  434          * At this point, the kmem_object must be unlocked because
  435          * vm_map_simplify_entry() calls vm_object_deallocate(), which
  436          * locks the kmem_object.
  437          */
  438         vm_map_simplify_entry(map, entry);
  439 
  440         /*
  441          * Loop thru pages, entering them in the pmap.
  442          */
  443         VM_OBJECT_LOCK(kmem_object);
  444         for (i = 0; i < size; i += PAGE_SIZE) {
  445                 m = vm_page_lookup(kmem_object, OFF_TO_IDX(offset + i));
  446                 /*
  447                  * Because this is kernel_pmap, this call will not block.
  448                  */
  449                 pmap_enter(kernel_pmap, addr + i, VM_PROT_ALL, m, VM_PROT_ALL,
  450                     TRUE);
  451                 vm_page_wakeup(m);
  452         }
  453         VM_OBJECT_UNLOCK(kmem_object);
  454 
  455         return (KERN_SUCCESS);
  456 }
  457 
  458 /*
  459  *      kmem_alloc_wait:
  460  *
  461  *      Allocates pageable memory from a sub-map of the kernel.  If the submap
  462  *      has no room, the caller sleeps waiting for more memory in the submap.
  463  *
  464  *      This routine may block.
  465  */
  466 vm_offset_t
  467 kmem_alloc_wait(map, size)
  468         vm_map_t map;
  469         vm_size_t size;
  470 {
  471         vm_offset_t addr;
  472 
  473         size = round_page(size);
  474         if (!swap_reserve(size))
  475                 return (0);
  476 
  477         for (;;) {
  478                 /*
  479                  * To make this work for more than one map, use the map's lock
  480                  * to lock out sleepers/wakers.
  481                  */
  482                 vm_map_lock(map);
  483                 if (vm_map_findspace(map, vm_map_min(map), size, &addr) == 0)
  484                         break;
  485                 /* no space now; see if we can ever get space */
  486                 if (vm_map_max(map) - vm_map_min(map) < size) {
  487                         vm_map_unlock(map);
  488                         swap_release(size);
  489                         return (0);
  490                 }
  491                 map->needs_wakeup = TRUE;
  492                 vm_map_unlock_and_wait(map, 0);
  493         }
  494         vm_map_insert(map, NULL, 0, addr, addr + size, VM_PROT_ALL,
  495             VM_PROT_ALL, MAP_ACC_CHARGED);
  496         vm_map_unlock(map);
  497         return (addr);
  498 }
  499 
  500 /*
  501  *      kmem_free_wakeup:
  502  *
  503  *      Returns memory to a submap of the kernel, and wakes up any processes
  504  *      waiting for memory in that map.
  505  */
  506 void
  507 kmem_free_wakeup(map, addr, size)
  508         vm_map_t map;
  509         vm_offset_t addr;
  510         vm_size_t size;
  511 {
  512 
  513         vm_map_lock(map);
  514         (void) vm_map_delete(map, trunc_page(addr), round_page(addr + size));
  515         if (map->needs_wakeup) {
  516                 map->needs_wakeup = FALSE;
  517                 vm_map_wakeup(map);
  518         }
  519         vm_map_unlock(map);
  520 }
  521 
  522 /*
  523  *      kmem_init:
  524  *
  525  *      Create the kernel map; insert a mapping covering kernel text, 
  526  *      data, bss, and all space allocated thus far (`boostrap' data).  The 
  527  *      new map will thus map the range between VM_MIN_KERNEL_ADDRESS and 
  528  *      `start' as allocated, and the range between `start' and `end' as free.
  529  */
  530 void
  531 kmem_init(start, end)
  532         vm_offset_t start, end;
  533 {
  534         vm_map_t m;
  535 
  536         m = vm_map_create(kernel_pmap, VM_MIN_KERNEL_ADDRESS, end);
  537         m->system_map = 1;
  538         vm_map_lock(m);
  539         /* N.B.: cannot use kgdb to debug, starting with this assignment ... */
  540         kernel_map = m;
  541         (void) vm_map_insert(m, NULL, (vm_ooffset_t) 0,
  542 #ifdef __amd64__
  543             KERNBASE,
  544 #else                
  545             VM_MIN_KERNEL_ADDRESS,
  546 #endif
  547             start, VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
  548         /* ... and ending with the completion of the above `insert' */
  549         vm_map_unlock(m);
  550 }
  551 
  552 #ifdef DIAGNOSTIC
  553 /*
  554  * Allow userspace to directly trigger the VM drain routine for testing
  555  * purposes.
  556  */
  557 static int
  558 debug_vm_lowmem(SYSCTL_HANDLER_ARGS)
  559 {
  560         int error, i;
  561 
  562         i = 0;
  563         error = sysctl_handle_int(oidp, &i, 0, req);
  564         if (error)
  565                 return (error);
  566         if (i)   
  567                 EVENTHANDLER_INVOKE(vm_lowmem, 0);
  568         return (0);
  569 }
  570 
  571 SYSCTL_PROC(_debug, OID_AUTO, vm_lowmem, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
  572     debug_vm_lowmem, "I", "set to trigger vm_lowmem event");
  573 #endif

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