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/8.1/sys/vm/vm_kern.c 199583 2009-11-20 15:27:52Z jhb $");
   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  *      Allocate wired-down memory in the kernel's address map
  123  *      or a submap.
  124  */
  125 vm_offset_t
  126 kmem_alloc(map, size)
  127         vm_map_t map;
  128         vm_size_t size;
  129 {
  130         vm_offset_t addr;
  131         vm_offset_t offset;
  132         vm_offset_t i;
  133 
  134         size = round_page(size);
  135 
  136         /*
  137          * Use the kernel object for wired-down kernel pages. Assume that no
  138          * region of the kernel object is referenced more than once.
  139          */
  140 
  141         /*
  142          * Locate sufficient space in the map.  This will give us the final
  143          * virtual address for the new memory, and thus will tell us the
  144          * offset within the kernel map.
  145          */
  146         vm_map_lock(map);
  147         if (vm_map_findspace(map, vm_map_min(map), size, &addr)) {
  148                 vm_map_unlock(map);
  149                 return (0);
  150         }
  151         offset = addr - VM_MIN_KERNEL_ADDRESS;
  152         vm_object_reference(kernel_object);
  153         vm_map_insert(map, kernel_object, offset, addr, addr + size,
  154                 VM_PROT_ALL, VM_PROT_ALL, 0);
  155         vm_map_unlock(map);
  156 
  157         /*
  158          * Guarantee that there are pages already in this object before
  159          * calling vm_map_wire.  This is to prevent the following
  160          * scenario:
  161          *
  162          * 1) Threads have swapped out, so that there is a pager for the
  163          * kernel_object. 2) The kmsg zone is empty, and so we are
  164          * kmem_allocing a new page for it. 3) vm_map_wire calls vm_fault;
  165          * there is no page, but there is a pager, so we call
  166          * pager_data_request.  But the kmsg zone is empty, so we must
  167          * kmem_alloc. 4) goto 1 5) Even if the kmsg zone is not empty: when
  168          * we get the data back from the pager, it will be (very stale)
  169          * non-zero data.  kmem_alloc is defined to return zero-filled memory.
  170          *
  171          * We're intentionally not activating the pages we allocate to prevent a
  172          * race with page-out.  vm_map_wire will wire the pages.
  173          */
  174         VM_OBJECT_LOCK(kernel_object);
  175         for (i = 0; i < size; i += PAGE_SIZE) {
  176                 vm_page_t mem;
  177 
  178                 mem = vm_page_grab(kernel_object, OFF_TO_IDX(offset + i),
  179                     VM_ALLOC_NOBUSY | VM_ALLOC_ZERO | VM_ALLOC_RETRY);
  180                 mem->valid = VM_PAGE_BITS_ALL;
  181                 KASSERT((mem->flags & PG_UNMANAGED) != 0,
  182                     ("kmem_alloc: page %p is managed", mem));
  183         }
  184         VM_OBJECT_UNLOCK(kernel_object);
  185 
  186         /*
  187          * And finally, mark the data as non-pageable.
  188          */
  189         (void) vm_map_wire(map, addr, addr + size,
  190             VM_MAP_WIRE_SYSTEM|VM_MAP_WIRE_NOHOLES);
  191 
  192         return (addr);
  193 }
  194 
  195 /*
  196  *      kmem_free:
  197  *
  198  *      Release a region of kernel virtual memory allocated
  199  *      with kmem_alloc, and return the physical pages
  200  *      associated with that region.
  201  *
  202  *      This routine may not block on kernel maps.
  203  */
  204 void
  205 kmem_free(map, addr, size)
  206         vm_map_t map;
  207         vm_offset_t addr;
  208         vm_size_t size;
  209 {
  210 
  211         (void) vm_map_remove(map, trunc_page(addr), round_page(addr + size));
  212 }
  213 
  214 /*
  215  *      kmem_suballoc:
  216  *
  217  *      Allocates a map to manage a subrange
  218  *      of the kernel virtual address space.
  219  *
  220  *      Arguments are as follows:
  221  *
  222  *      parent          Map to take range from
  223  *      min, max        Returned endpoints of map
  224  *      size            Size of range to find
  225  *      superpage_align Request that min is superpage aligned
  226  */
  227 vm_map_t
  228 kmem_suballoc(vm_map_t parent, vm_offset_t *min, vm_offset_t *max,
  229     vm_size_t size, boolean_t superpage_align)
  230 {
  231         int ret;
  232         vm_map_t result;
  233 
  234         size = round_page(size);
  235 
  236         *min = vm_map_min(parent);
  237         ret = vm_map_find(parent, NULL, 0, min, size, superpage_align ?
  238             VMFS_ALIGNED_SPACE : VMFS_ANY_SPACE, VM_PROT_ALL, VM_PROT_ALL,
  239             MAP_ACC_NO_CHARGE);
  240         if (ret != KERN_SUCCESS)
  241                 panic("kmem_suballoc: bad status return of %d", ret);
  242         *max = *min + size;
  243         result = vm_map_create(vm_map_pmap(parent), *min, *max);
  244         if (result == NULL)
  245                 panic("kmem_suballoc: cannot create submap");
  246         if (vm_map_submap(parent, *min, *max, result) != KERN_SUCCESS)
  247                 panic("kmem_suballoc: unable to change range to submap");
  248         return (result);
  249 }
  250 
  251 /*
  252  *      kmem_malloc:
  253  *
  254  *      Allocate wired-down memory in the kernel's address map for the higher
  255  *      level kernel memory allocator (kern/kern_malloc.c).  We cannot use
  256  *      kmem_alloc() because we may need to allocate memory at interrupt
  257  *      level where we cannot block (canwait == FALSE).
  258  *
  259  *      This routine has its own private kernel submap (kmem_map) and object
  260  *      (kmem_object).  This, combined with the fact that only malloc uses
  261  *      this routine, ensures that we will never block in map or object waits.
  262  *
  263  *      We don't worry about expanding the map (adding entries) since entries
  264  *      for wired maps are statically allocated.
  265  *
  266  *      `map' is ONLY allowed to be kmem_map or one of the mbuf submaps to
  267  *      which we never free.
  268  */
  269 vm_offset_t
  270 kmem_malloc(map, size, flags)
  271         vm_map_t map;
  272         vm_size_t size;
  273         int flags;
  274 {
  275         vm_offset_t offset, i;
  276         vm_map_entry_t entry;
  277         vm_offset_t addr;
  278         vm_page_t m;
  279         int pflags;
  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         offset = addr - VM_MIN_KERNEL_ADDRESS;
  313         vm_object_reference(kmem_object);
  314         vm_map_insert(map, kmem_object, offset, addr, addr + size,
  315                 VM_PROT_ALL, VM_PROT_ALL, 0);
  316 
  317         if ((flags & (M_NOWAIT|M_USE_RESERVE)) == M_NOWAIT)
  318                 pflags = VM_ALLOC_INTERRUPT | VM_ALLOC_WIRED;
  319         else
  320                 pflags = VM_ALLOC_SYSTEM | VM_ALLOC_WIRED;
  321 
  322         if (flags & M_ZERO)
  323                 pflags |= VM_ALLOC_ZERO;
  324 
  325         VM_OBJECT_LOCK(kmem_object);
  326         for (i = 0; i < size; i += PAGE_SIZE) {
  327 retry:
  328                 m = vm_page_alloc(kmem_object, OFF_TO_IDX(offset + i), pflags);
  329 
  330                 /*
  331                  * Ran out of space, free everything up and return. Don't need
  332                  * to lock page queues here as we know that the pages we got
  333                  * aren't on any queues.
  334                  */
  335                 if (m == NULL) {
  336                         if ((flags & M_NOWAIT) == 0) {
  337                                 VM_OBJECT_UNLOCK(kmem_object);
  338                                 vm_map_unlock(map);
  339                                 VM_WAIT;
  340                                 vm_map_lock(map);
  341                                 VM_OBJECT_LOCK(kmem_object);
  342                                 goto retry;
  343                         }
  344                         /* 
  345                          * Free the pages before removing the map entry.
  346                          * They are already marked busy.  Calling
  347                          * vm_map_delete before the pages has been freed or
  348                          * unbusied will cause a deadlock.
  349                          */
  350                         while (i != 0) {
  351                                 i -= PAGE_SIZE;
  352                                 m = vm_page_lookup(kmem_object,
  353                                                    OFF_TO_IDX(offset + i));
  354                                 vm_page_lock_queues();
  355                                 vm_page_unwire(m, 0);
  356                                 vm_page_free(m);
  357                                 vm_page_unlock_queues();
  358                         }
  359                         VM_OBJECT_UNLOCK(kmem_object);
  360                         vm_map_delete(map, addr, addr + size);
  361                         vm_map_unlock(map);
  362                         return (0);
  363                 }
  364                 if (flags & M_ZERO && (m->flags & PG_ZERO) == 0)
  365                         pmap_zero_page(m);
  366                 m->valid = VM_PAGE_BITS_ALL;
  367                 KASSERT((m->flags & PG_UNMANAGED) != 0,
  368                     ("kmem_malloc: page %p is managed", m));
  369         }
  370         VM_OBJECT_UNLOCK(kmem_object);
  371 
  372         /*
  373          * Mark map entry as non-pageable. Assert: vm_map_insert() will never
  374          * be able to extend the previous entry so there will be a new entry
  375          * exactly corresponding to this address range and it will have
  376          * wired_count == 0.
  377          */
  378         if (!vm_map_lookup_entry(map, addr, &entry) ||
  379             entry->start != addr || entry->end != addr + size ||
  380             entry->wired_count != 0)
  381                 panic("kmem_malloc: entry not found or misaligned");
  382         entry->wired_count = 1;
  383 
  384         /*
  385          * At this point, the kmem_object must be unlocked because
  386          * vm_map_simplify_entry() calls vm_object_deallocate(), which
  387          * locks the kmem_object.
  388          */
  389         vm_map_simplify_entry(map, entry);
  390 
  391         /*
  392          * Loop thru pages, entering them in the pmap.
  393          */
  394         VM_OBJECT_LOCK(kmem_object);
  395         for (i = 0; i < size; i += PAGE_SIZE) {
  396                 m = vm_page_lookup(kmem_object, OFF_TO_IDX(offset + i));
  397                 /*
  398                  * Because this is kernel_pmap, this call will not block.
  399                  */
  400                 pmap_enter(kernel_pmap, addr + i, VM_PROT_ALL, m, VM_PROT_ALL,
  401                     TRUE);
  402                 vm_page_wakeup(m);
  403         }
  404         VM_OBJECT_UNLOCK(kmem_object);
  405         vm_map_unlock(map);
  406 
  407         return (addr);
  408 }
  409 
  410 /*
  411  *      kmem_alloc_wait:
  412  *
  413  *      Allocates pageable memory from a sub-map of the kernel.  If the submap
  414  *      has no room, the caller sleeps waiting for more memory in the submap.
  415  *
  416  *      This routine may block.
  417  */
  418 vm_offset_t
  419 kmem_alloc_wait(map, size)
  420         vm_map_t map;
  421         vm_size_t size;
  422 {
  423         vm_offset_t addr;
  424 
  425         size = round_page(size);
  426         if (!swap_reserve(size))
  427                 return (0);
  428 
  429         for (;;) {
  430                 /*
  431                  * To make this work for more than one map, use the map's lock
  432                  * to lock out sleepers/wakers.
  433                  */
  434                 vm_map_lock(map);
  435                 if (vm_map_findspace(map, vm_map_min(map), size, &addr) == 0)
  436                         break;
  437                 /* no space now; see if we can ever get space */
  438                 if (vm_map_max(map) - vm_map_min(map) < size) {
  439                         vm_map_unlock(map);
  440                         swap_release(size);
  441                         return (0);
  442                 }
  443                 map->needs_wakeup = TRUE;
  444                 vm_map_unlock_and_wait(map, 0);
  445         }
  446         vm_map_insert(map, NULL, 0, addr, addr + size, VM_PROT_ALL,
  447             VM_PROT_ALL, MAP_ACC_CHARGED);
  448         vm_map_unlock(map);
  449         return (addr);
  450 }
  451 
  452 /*
  453  *      kmem_free_wakeup:
  454  *
  455  *      Returns memory to a submap of the kernel, and wakes up any processes
  456  *      waiting for memory in that map.
  457  */
  458 void
  459 kmem_free_wakeup(map, addr, size)
  460         vm_map_t map;
  461         vm_offset_t addr;
  462         vm_size_t size;
  463 {
  464 
  465         vm_map_lock(map);
  466         (void) vm_map_delete(map, trunc_page(addr), round_page(addr + size));
  467         if (map->needs_wakeup) {
  468                 map->needs_wakeup = FALSE;
  469                 vm_map_wakeup(map);
  470         }
  471         vm_map_unlock(map);
  472 }
  473 
  474 /*
  475  *      kmem_init:
  476  *
  477  *      Create the kernel map; insert a mapping covering kernel text, 
  478  *      data, bss, and all space allocated thus far (`boostrap' data).  The 
  479  *      new map will thus map the range between VM_MIN_KERNEL_ADDRESS and 
  480  *      `start' as allocated, and the range between `start' and `end' as free.
  481  */
  482 void
  483 kmem_init(start, end)
  484         vm_offset_t start, end;
  485 {
  486         vm_map_t m;
  487 
  488         m = vm_map_create(kernel_pmap, VM_MIN_KERNEL_ADDRESS, end);
  489         m->system_map = 1;
  490         vm_map_lock(m);
  491         /* N.B.: cannot use kgdb to debug, starting with this assignment ... */
  492         kernel_map = m;
  493         (void) vm_map_insert(m, NULL, (vm_ooffset_t) 0,
  494 #ifdef __amd64__
  495             KERNBASE,
  496 #else                
  497             VM_MIN_KERNEL_ADDRESS,
  498 #endif
  499             start, VM_PROT_ALL, VM_PROT_ALL, MAP_NOFAULT);
  500         /* ... and ending with the completion of the above `insert' */
  501         vm_map_unlock(m);
  502 }
  503 
  504 #ifdef DIAGNOSTIC
  505 /*
  506  * Allow userspace to directly trigger the VM drain routine for testing
  507  * purposes.
  508  */
  509 static int
  510 debug_vm_lowmem(SYSCTL_HANDLER_ARGS)
  511 {
  512         int error, i;
  513 
  514         i = 0;
  515         error = sysctl_handle_int(oidp, &i, 0, req);
  516         if (error)
  517                 return (error);
  518         if (i)   
  519                 EVENTHANDLER_INVOKE(vm_lowmem, 0);
  520         return (0);
  521 }
  522 
  523 SYSCTL_PROC(_debug, OID_AUTO, vm_lowmem, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
  524     debug_vm_lowmem, "I", "set to trigger vm_lowmem event");
  525 #endif

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