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/9.2/sys/vm/vm_kern.c 251897 2013-06-18 05:21:40Z scottl $");
   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;
   89 vm_map_t kmem_map;
   90 vm_map_t exec_map;
   91 vm_map_t pipe_map;
   92 vm_map_t buffer_map;
   93 vm_map_t bio_transient_map;
   94 
   95 const void *zero_region;
   96 CTASSERT((ZERO_REGION_SIZE & PAGE_MASK) == 0);
   97 
   98 /*
   99  *      kmem_alloc_nofault:
  100  *
  101  *      Allocate a virtual address range with no underlying object and
  102  *      no initial mapping to physical memory.  Any mapping from this
  103  *      range to physical memory must be explicitly created prior to
  104  *      its use, typically with pmap_qenter().  Any attempt to create
  105  *      a mapping on demand through vm_fault() will result in a panic. 
  106  */
  107 vm_offset_t
  108 kmem_alloc_nofault(map, size)
  109         vm_map_t map;
  110         vm_size_t size;
  111 {
  112         vm_offset_t addr;
  113         int result;
  114 
  115         size = round_page(size);
  116         addr = vm_map_min(map);
  117         result = vm_map_find(map, NULL, 0, &addr, size, VMFS_ANY_SPACE,
  118             VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
  119         if (result != KERN_SUCCESS) {
  120                 return (0);
  121         }
  122         return (addr);
  123 }
  124 
  125 /*
  126  *      kmem_alloc_nofault_space:
  127  *
  128  *      Allocate a virtual address range with no underlying object and
  129  *      no initial mapping to physical memory within the specified
  130  *      address space.  Any mapping from this range to physical memory
  131  *      must be explicitly created prior to its use, typically with
  132  *      pmap_qenter().  Any attempt to create a mapping on demand
  133  *      through vm_fault() will result in a panic. 
  134  */
  135 vm_offset_t
  136 kmem_alloc_nofault_space(map, size, find_space)
  137         vm_map_t map;
  138         vm_size_t size;
  139         int find_space;
  140 {
  141         vm_offset_t addr;
  142         int result;
  143 
  144         size = round_page(size);
  145         addr = vm_map_min(map);
  146         result = vm_map_find(map, NULL, 0, &addr, size, find_space,
  147             VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
  148         if (result != KERN_SUCCESS) {
  149                 return (0);
  150         }
  151         return (addr);
  152 }
  153 
  154 /*
  155  *      Allocate wired-down memory in the kernel's address map
  156  *      or a submap.
  157  */
  158 vm_offset_t
  159 kmem_alloc(map, size)
  160         vm_map_t map;
  161         vm_size_t size;
  162 {
  163         vm_offset_t addr;
  164         vm_offset_t offset;
  165 
  166         size = round_page(size);
  167 
  168         /*
  169          * Use the kernel object for wired-down kernel pages. Assume that no
  170          * region of the kernel object is referenced more than once.
  171          */
  172 
  173         /*
  174          * Locate sufficient space in the map.  This will give us the final
  175          * virtual address for the new memory, and thus will tell us the
  176          * offset within the kernel map.
  177          */
  178         vm_map_lock(map);
  179         if (vm_map_findspace(map, vm_map_min(map), size, &addr)) {
  180                 vm_map_unlock(map);
  181                 return (0);
  182         }
  183         offset = addr - VM_MIN_KERNEL_ADDRESS;
  184         vm_object_reference(kernel_object);
  185         vm_map_insert(map, kernel_object, offset, addr, addr + size,
  186                 VM_PROT_ALL, VM_PROT_ALL, 0);
  187         vm_map_unlock(map);
  188 
  189         /*
  190          * And finally, mark the data as non-pageable.
  191          */
  192         (void) vm_map_wire(map, addr, addr + size,
  193             VM_MAP_WIRE_SYSTEM|VM_MAP_WIRE_NOHOLES);
  194 
  195         return (addr);
  196 }
  197 
  198 /*
  199  *      kmem_free:
  200  *
  201  *      Release a region of kernel virtual memory allocated
  202  *      with kmem_alloc, and return the physical pages
  203  *      associated with that region.
  204  *
  205  *      This routine may not block on kernel maps.
  206  */
  207 void
  208 kmem_free(map, addr, size)
  209         vm_map_t map;
  210         vm_offset_t addr;
  211         vm_size_t size;
  212 {
  213 
  214         (void) vm_map_remove(map, trunc_page(addr), round_page(addr + size));
  215 }
  216 
  217 /*
  218  *      kmem_suballoc:
  219  *
  220  *      Allocates a map to manage a subrange
  221  *      of the kernel virtual address space.
  222  *
  223  *      Arguments are as follows:
  224  *
  225  *      parent          Map to take range from
  226  *      min, max        Returned endpoints of map
  227  *      size            Size of range to find
  228  *      superpage_align Request that min is superpage aligned
  229  */
  230 vm_map_t
  231 kmem_suballoc(vm_map_t parent, vm_offset_t *min, vm_offset_t *max,
  232     vm_size_t size, boolean_t superpage_align)
  233 {
  234         int ret;
  235         vm_map_t result;
  236 
  237         size = round_page(size);
  238 
  239         *min = vm_map_min(parent);
  240         ret = vm_map_find(parent, NULL, 0, min, size, superpage_align ?
  241             VMFS_ALIGNED_SPACE : VMFS_ANY_SPACE, VM_PROT_ALL, VM_PROT_ALL,
  242             MAP_ACC_NO_CHARGE);
  243         if (ret != KERN_SUCCESS)
  244                 panic("kmem_suballoc: bad status return of %d", ret);
  245         *max = *min + size;
  246         result = vm_map_create(vm_map_pmap(parent), *min, *max);
  247         if (result == NULL)
  248                 panic("kmem_suballoc: cannot create submap");
  249         if (vm_map_submap(parent, *min, *max, result) != KERN_SUCCESS)
  250                 panic("kmem_suballoc: unable to change range to submap");
  251         return (result);
  252 }
  253 
  254 /*
  255  *      kmem_malloc:
  256  *
  257  *      Allocate wired-down memory in the kernel's address map for the higher
  258  *      level kernel memory allocator (kern/kern_malloc.c).  We cannot use
  259  *      kmem_alloc() because we may need to allocate memory at interrupt
  260  *      level where we cannot block (canwait == FALSE).
  261  *
  262  *      This routine has its own private kernel submap (kmem_map) and object
  263  *      (kmem_object).  This, combined with the fact that only malloc uses
  264  *      this routine, ensures that we will never block in map or object waits.
  265  *
  266  *      We don't worry about expanding the map (adding entries) since entries
  267  *      for wired maps are statically allocated.
  268  *
  269  *      `map' is ONLY allowed to be kmem_map or one of the mbuf submaps to
  270  *      which we never free.
  271  */
  272 vm_offset_t
  273 kmem_malloc(map, size, flags)
  274         vm_map_t map;
  275         vm_size_t size;
  276         int flags;
  277 {
  278         vm_offset_t addr;
  279         int i, rv;
  280 
  281         size = round_page(size);
  282         addr = vm_map_min(map);
  283 
  284         /*
  285          * Locate sufficient space in the map.  This will give us the final
  286          * virtual address for the new memory, and thus will tell us the
  287          * offset within the kernel map.
  288          */
  289         vm_map_lock(map);
  290         if (vm_map_findspace(map, vm_map_min(map), size, &addr)) {
  291                 vm_map_unlock(map);
  292                 if ((flags & M_NOWAIT) == 0) {
  293                         for (i = 0; i < 8; i++) {
  294                                 EVENTHANDLER_INVOKE(vm_lowmem, 0);
  295                                 uma_reclaim();
  296                                 vm_map_lock(map);
  297                                 if (vm_map_findspace(map, vm_map_min(map),
  298                                     size, &addr) == 0) {
  299                                         break;
  300                                 }
  301                                 vm_map_unlock(map);
  302                                 tsleep(&i, 0, "nokva", (hz / 4) * (i + 1));
  303                         }
  304                         if (i == 8) {
  305                                 panic("kmem_malloc(%ld): kmem_map too small: %ld total allocated",
  306                                     (long)size, (long)map->size);
  307                         }
  308                 } else {
  309                         return (0);
  310                 }
  311         }
  312 
  313         rv = kmem_back(map, addr, size, flags);
  314         vm_map_unlock(map);
  315         return (rv == KERN_SUCCESS ? addr : 0);
  316 }
  317 
  318 /*
  319  *      kmem_back:
  320  *
  321  *      Allocate physical pages for the specified virtual address range.
  322  */
  323 int
  324 kmem_back(vm_map_t map, vm_offset_t addr, vm_size_t size, int flags)
  325 {
  326         vm_offset_t offset, i;
  327         vm_map_entry_t entry;
  328         vm_page_t m;
  329         int pflags;
  330         boolean_t found;
  331 
  332         KASSERT(vm_map_locked(map), ("kmem_back: map %p is not locked", map));
  333         offset = addr - VM_MIN_KERNEL_ADDRESS;
  334         vm_object_reference(kmem_object);
  335         vm_map_insert(map, kmem_object, offset, addr, addr + size,
  336             VM_PROT_ALL, VM_PROT_ALL, 0);
  337 
  338         /*
  339          * Assert: vm_map_insert() will never be able to extend the
  340          * previous entry so vm_map_lookup_entry() will find a new
  341          * entry exactly corresponding to this address range and it
  342          * will have wired_count == 0.
  343          */
  344         found = vm_map_lookup_entry(map, addr, &entry);
  345         KASSERT(found && entry->start == addr && entry->end == addr + size &&
  346             entry->wired_count == 0 && (entry->eflags & MAP_ENTRY_IN_TRANSITION)
  347             == 0, ("kmem_back: entry not found or misaligned"));
  348 
  349         if ((flags & (M_NOWAIT|M_USE_RESERVE)) == M_NOWAIT)
  350                 pflags = VM_ALLOC_INTERRUPT | VM_ALLOC_WIRED;
  351         else
  352                 pflags = VM_ALLOC_SYSTEM | VM_ALLOC_WIRED;
  353 
  354         if (flags & M_ZERO)
  355                 pflags |= VM_ALLOC_ZERO;
  356         if (flags & M_NODUMP)
  357                 pflags |= VM_ALLOC_NODUMP;
  358 
  359         VM_OBJECT_LOCK(kmem_object);
  360         for (i = 0; i < size; i += PAGE_SIZE) {
  361 retry:
  362                 m = vm_page_alloc(kmem_object, OFF_TO_IDX(offset + i), pflags);
  363 
  364                 /*
  365                  * Ran out of space, free everything up and return. Don't need
  366                  * to lock page queues here as we know that the pages we got
  367                  * aren't on any queues.
  368                  */
  369                 if (m == NULL) {
  370                         if ((flags & M_NOWAIT) == 0) {
  371                                 VM_OBJECT_UNLOCK(kmem_object);
  372                                 entry->eflags |= MAP_ENTRY_IN_TRANSITION;
  373                                 vm_map_unlock(map);
  374                                 VM_WAIT;
  375                                 vm_map_lock(map);
  376                                 KASSERT(
  377 (entry->eflags & (MAP_ENTRY_IN_TRANSITION | MAP_ENTRY_NEEDS_WAKEUP)) ==
  378                                     MAP_ENTRY_IN_TRANSITION,
  379                                     ("kmem_back: volatile entry"));
  380                                 entry->eflags &= ~MAP_ENTRY_IN_TRANSITION;
  381                                 VM_OBJECT_LOCK(kmem_object);
  382                                 goto retry;
  383                         }
  384                         /* 
  385                          * Free the pages before removing the map entry.
  386                          * They are already marked busy.  Calling
  387                          * vm_map_delete before the pages has been freed or
  388                          * unbusied will cause a deadlock.
  389                          */
  390                         while (i != 0) {
  391                                 i -= PAGE_SIZE;
  392                                 m = vm_page_lookup(kmem_object,
  393                                                    OFF_TO_IDX(offset + i));
  394                                 vm_page_unwire(m, 0);
  395                                 vm_page_free(m);
  396                         }
  397                         VM_OBJECT_UNLOCK(kmem_object);
  398                         vm_map_delete(map, addr, addr + size);
  399                         return (KERN_NO_SPACE);
  400                 }
  401                 if (flags & M_ZERO && (m->flags & PG_ZERO) == 0)
  402                         pmap_zero_page(m);
  403                 m->valid = VM_PAGE_BITS_ALL;
  404                 KASSERT((m->oflags & VPO_UNMANAGED) != 0,
  405                     ("kmem_malloc: page %p is managed", m));
  406         }
  407         VM_OBJECT_UNLOCK(kmem_object);
  408 
  409         /*
  410          * Mark map entry as non-pageable.  Repeat the assert.
  411          */
  412         KASSERT(entry->start == addr && entry->end == addr + size &&
  413             entry->wired_count == 0,
  414             ("kmem_back: entry not found or misaligned after allocation"));
  415         entry->wired_count = 1;
  416 
  417         /*
  418          * At this point, the kmem_object must be unlocked because
  419          * vm_map_simplify_entry() calls vm_object_deallocate(), which
  420          * locks the kmem_object.
  421          */
  422         vm_map_simplify_entry(map, entry);
  423 
  424         /*
  425          * Loop thru pages, entering them in the pmap.
  426          */
  427         VM_OBJECT_LOCK(kmem_object);
  428         for (i = 0; i < size; i += PAGE_SIZE) {
  429                 m = vm_page_lookup(kmem_object, OFF_TO_IDX(offset + i));
  430                 /*
  431                  * Because this is kernel_pmap, this call will not block.
  432                  */
  433                 pmap_enter(kernel_pmap, addr + i, VM_PROT_ALL, m, VM_PROT_ALL,
  434                     TRUE);
  435                 vm_page_wakeup(m);
  436         }
  437         VM_OBJECT_UNLOCK(kmem_object);
  438 
  439         return (KERN_SUCCESS);
  440 }
  441 
  442 /*
  443  *      kmem_alloc_wait:
  444  *
  445  *      Allocates pageable memory from a sub-map of the kernel.  If the submap
  446  *      has no room, the caller sleeps waiting for more memory in the submap.
  447  *
  448  *      This routine may block.
  449  */
  450 vm_offset_t
  451 kmem_alloc_wait(map, size)
  452         vm_map_t map;
  453         vm_size_t size;
  454 {
  455         vm_offset_t addr;
  456 
  457         size = round_page(size);
  458         if (!swap_reserve(size))
  459                 return (0);
  460 
  461         for (;;) {
  462                 /*
  463                  * To make this work for more than one map, use the map's lock
  464                  * to lock out sleepers/wakers.
  465                  */
  466                 vm_map_lock(map);
  467                 if (vm_map_findspace(map, vm_map_min(map), size, &addr) == 0)
  468                         break;
  469                 /* no space now; see if we can ever get space */
  470                 if (vm_map_max(map) - vm_map_min(map) < size) {
  471                         vm_map_unlock(map);
  472                         swap_release(size);
  473                         return (0);
  474                 }
  475                 map->needs_wakeup = TRUE;
  476                 vm_map_unlock_and_wait(map, 0);
  477         }
  478         vm_map_insert(map, NULL, 0, addr, addr + size, VM_PROT_ALL,
  479             VM_PROT_ALL, MAP_ACC_CHARGED);
  480         vm_map_unlock(map);
  481         return (addr);
  482 }
  483 
  484 /*
  485  *      kmem_free_wakeup:
  486  *
  487  *      Returns memory to a submap of the kernel, and wakes up any processes
  488  *      waiting for memory in that map.
  489  */
  490 void
  491 kmem_free_wakeup(map, addr, size)
  492         vm_map_t map;
  493         vm_offset_t addr;
  494         vm_size_t size;
  495 {
  496 
  497         vm_map_lock(map);
  498         (void) vm_map_delete(map, trunc_page(addr), round_page(addr + size));
  499         if (map->needs_wakeup) {
  500                 map->needs_wakeup = FALSE;
  501                 vm_map_wakeup(map);
  502         }
  503         vm_map_unlock(map);
  504 }
  505 
  506 static void
  507 kmem_init_zero_region(void)
  508 {
  509         vm_offset_t addr, i;
  510         vm_page_t m;
  511         int error;
  512 
  513         /*
  514          * Map a single physical page of zeros to a larger virtual range.
  515          * This requires less looping in places that want large amounts of
  516          * zeros, while not using much more physical resources.
  517          */
  518         addr = kmem_alloc_nofault(kernel_map, ZERO_REGION_SIZE);
  519         m = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL |
  520             VM_ALLOC_NOOBJ | VM_ALLOC_WIRED | VM_ALLOC_ZERO);
  521         if ((m->flags & PG_ZERO) == 0)
  522                 pmap_zero_page(m);
  523         for (i = 0; i < ZERO_REGION_SIZE; i += PAGE_SIZE)
  524                 pmap_qenter(addr + i, &m, 1);
  525         error = vm_map_protect(kernel_map, addr, addr + ZERO_REGION_SIZE,
  526             VM_PROT_READ, TRUE);
  527         KASSERT(error == 0, ("error=%d", error));
  528 
  529         zero_region = (const void *)addr;
  530 }
  531 
  532 /*
  533  *      kmem_init:
  534  *
  535  *      Create the kernel map; insert a mapping covering kernel text, 
  536  *      data, bss, and all space allocated thus far (`boostrap' data).  The 
  537  *      new map will thus map the range between VM_MIN_KERNEL_ADDRESS and 
  538  *      `start' as allocated, and the range between `start' and `end' as free.
  539  */
  540 void
  541 kmem_init(start, end)
  542         vm_offset_t start, end;
  543 {
  544         vm_map_t m;
  545 
  546         m = vm_map_create(kernel_pmap, VM_MIN_KERNEL_ADDRESS, end);
  547         m->system_map = 1;
  548         vm_map_lock(m);
  549         /* N.B.: cannot use kgdb to debug, starting with this assignment ... */
  550         kernel_map = m;
  551         (void) vm_map_insert(m, NULL, (vm_ooffset_t) 0,
  552 #ifdef __amd64__
  553             KERNBASE,
  554 #else                
  555             VM_MIN_KERNEL_ADDRESS,
  556 #endif
  557             start, VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
  558         /* ... and ending with the completion of the above `insert' */
  559         vm_map_unlock(m);
  560 
  561         kmem_init_zero_region();
  562 }
  563 
  564 #ifdef DIAGNOSTIC
  565 /*
  566  * Allow userspace to directly trigger the VM drain routine for testing
  567  * purposes.
  568  */
  569 static int
  570 debug_vm_lowmem(SYSCTL_HANDLER_ARGS)
  571 {
  572         int error, i;
  573 
  574         i = 0;
  575         error = sysctl_handle_int(oidp, &i, 0, req);
  576         if (error)
  577                 return (error);
  578         if (i)   
  579                 EVENTHANDLER_INVOKE(vm_lowmem, 0);
  580         return (0);
  581 }
  582 
  583 SYSCTL_PROC(_debug, OID_AUTO, vm_lowmem, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
  584     debug_vm_lowmem, "I", "set to trigger vm_lowmem event");
  585 #endif

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