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

     /*
      * Copyright (c) 1991, 1993
      *      The Regents of the University of California.  All rights reserved.
      *
      * This code is derived from software contributed to Berkeley by
      * The Mach Operating System project at Carnegie-Mellon University.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. All advertising materials mentioning features or use of this software
     *    must display the following acknowledgement:
     *      This product includes software developed by the University of
     *      California, Berkeley and its contributors.
     * 4. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      from: @(#)vm_object.c   8.5 (Berkeley) 3/22/94
     *
     *
     * Copyright (c) 1987, 1990 Carnegie-Mellon University.
     * All rights reserved.
     *
     * Authors: Avadis Tevanian, Jr., Michael Wayne Young
     *
     * Permission to use, copy, modify and distribute this software and
     * its documentation is hereby granted, provided that both the copyright
     * notice and this permission notice appear in all copies of the
     * software, derivative works or modified versions, and any portions
     * thereof, and that both notices appear in supporting documentation.
     *
     * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
     * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
     * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
     *
     * Carnegie Mellon requests users of this software to return to
     *
     *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
     *  School of Computer Science
     *  Carnegie Mellon University
     *  Pittsburgh PA 15213-3890
     *
     * any improvements or extensions that they make and grant Carnegie the
     * rights to redistribute these changes.
     *
     * $FreeBSD$
     */
    
    /*
     *      Virtual memory object module.
     */
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/proc.h>           /* for curproc, pageproc */
    #include <sys/vnode.h>
    #include <sys/vmmeter.h>
    #include <sys/mman.h>
    #include <sys/mount.h>
    
    #include <vm/vm.h>
    #include <vm/vm_param.h>
    #include <vm/vm_prot.h>
    #include <vm/pmap.h>
    #include <vm/vm_map.h>
    #include <vm/vm_object.h>
    #include <vm/vm_page.h>
    #include <vm/vm_pageout.h>
    #include <vm/vm_pager.h>
    #include <vm/swap_pager.h>
    #include <vm/vm_kern.h>
    #include <vm/vm_extern.h>
    #include <vm/vm_zone.h>
    
    static void     vm_object_qcollapse __P((vm_object_t object));
    
    /*
     *      Virtual memory objects maintain the actual data
     *      associated with allocated virtual memory.  A given
     *      page of memory exists within exactly one object.
     *
    *      An object is only deallocated when all "references"
    *      are given up.  Only one "reference" to a given
    *      region of an object should be writeable.
    *
    *      Associated with each object is a list of all resident
    *      memory pages belonging to that object; this list is
    *      maintained by the "vm_page" module, and locked by the object's
    *      lock.
    *
    *      Each object also records a "pager" routine which is
    *      used to retrieve (and store) pages to the proper backing
    *      storage.  In addition, objects may be backed by other
    *      objects from which they were virtual-copied.
    *
    *      The only items within the object structure which are
    *      modified after time of creation are:
    *              reference count         locked by object's lock
    *              pager routine           locked by object's lock
    *
    */
   
   struct object_q vm_object_list;
   #ifndef NULL_SIMPLELOCKS
   static struct simplelock vm_object_list_lock;
   #endif
   static long vm_object_count;            /* count of all objects */
   vm_object_t kernel_object;
   vm_object_t kmem_object;
   static struct vm_object kernel_object_store;
   static struct vm_object kmem_object_store;
   extern int vm_pageout_page_count;
   
   static long object_collapses;
   static long object_bypasses;
   static int next_index;
   static vm_zone_t obj_zone;
   static struct vm_zone obj_zone_store;
   #define VM_OBJECTS_INIT 256
   static struct vm_object vm_objects_init[VM_OBJECTS_INIT];
   static int objidnumber;
   
   void
   _vm_object_allocate(type, size, object)
           objtype_t type;
           vm_size_t size;
           register vm_object_t object;
   {
           int incr;
           TAILQ_INIT(&object->memq);
           TAILQ_INIT(&object->shadow_head);
   
           object->type = type;
           object->size = size;
           object->ref_count = 1;
           object->flags = 0;
           object->id = ++objidnumber;
           if ((object->type == OBJT_DEFAULT) || (object->type == OBJT_SWAP))
                   vm_object_set_flag(object, OBJ_ONEMAPPING);
           object->behavior = OBJ_NORMAL;
           object->paging_in_progress = 0;
           object->resident_page_count = 0;
           object->shadow_count = 0;
           object->pg_color = next_index;
           if ( size > (PQ_L2_SIZE / 3 + PQ_PRIME1))
                   incr = PQ_L2_SIZE / 3 + PQ_PRIME1;
           else
                   incr = size;
           next_index = (next_index + incr) & PQ_L2_MASK;
           object->handle = NULL;
           object->paging_offset = (vm_ooffset_t) 0;
           object->backing_object = NULL;
           object->backing_object_offset = (vm_ooffset_t) 0;
           object->page_hint = NULL;
   
           object->last_read = 0;
           object->generation++;
   
           TAILQ_INSERT_TAIL(&vm_object_list, object, object_list);
           vm_object_count++;
   }
   
   /*
    *      vm_object_init:
    *
    *      Initialize the VM objects module.
    */
   void
   vm_object_init()
   {
           TAILQ_INIT(&vm_object_list);
           simple_lock_init(&vm_object_list_lock);
           vm_object_count = 0;
           
           kernel_object = &kernel_object_store;
           _vm_object_allocate(OBJT_DEFAULT, OFF_TO_IDX(VM_MAX_KERNEL_ADDRESS - VM_MIN_KERNEL_ADDRESS),
               kernel_object);
   
           kmem_object = &kmem_object_store;
           _vm_object_allocate(OBJT_DEFAULT, OFF_TO_IDX(VM_MAX_KERNEL_ADDRESS - VM_MIN_KERNEL_ADDRESS),
               kmem_object);
   
           obj_zone = &obj_zone_store;
           zbootinit(obj_zone, "VM OBJECT", sizeof (struct vm_object),
                   vm_objects_init, VM_OBJECTS_INIT);
   }
   
   void
   vm_object_init2() {
           zinitna(obj_zone, NULL, NULL, 0, 0, 0, 1);
   }
   
   /*
    *      vm_object_allocate:
    *
    *      Returns a new object with the given size.
    */
   
   vm_object_t
   vm_object_allocate(type, size)
           objtype_t type;
           vm_size_t size;
   {
           register vm_object_t result;
           result = (vm_object_t) zalloc(obj_zone);
   
           _vm_object_allocate(type, size, result);
   
           return (result);
   }
   
   
   /*
    *      vm_object_reference:
    *
    *      Gets another reference to the given object.
    */
   void
   vm_object_reference(object)
           register vm_object_t object;
   {
           if (object == NULL)
                   return;
   
           KASSERT(!(object->flags & OBJ_DEAD),
               ("vm_object_reference: attempting to reference dead obj"));
   
           object->ref_count++;
           if (object->type == OBJT_VNODE) {
                   while (vget((struct vnode *) object->handle, LK_RETRY|LK_NOOBJ, curproc)) {
   #if !defined(MAX_PERF)
                           printf("vm_object_reference: delay in getting object\n");
   #endif
                   }
           }
   }
   
   void
   vm_object_vndeallocate(object)
           vm_object_t object;
   {
           struct vnode *vp = (struct vnode *) object->handle;
   
           KASSERT(object->type == OBJT_VNODE,
               ("vm_object_vndeallocate: not a vnode object"));
           KASSERT(vp != NULL, ("vm_object_vndeallocate: missing vp"));
   #ifdef INVARIANTS
           if (object->ref_count == 0) {
                   vprint("vm_object_vndeallocate", vp);
                   panic("vm_object_vndeallocate: bad object reference count");
           }
   #endif
   
           object->ref_count--;
           if (object->ref_count == 0) {
                   vp->v_flag &= ~VTEXT;
                   vm_object_clear_flag(object, OBJ_OPT);
           }
           vrele(vp);
   }
   
   /*
    *      vm_object_deallocate:
    *
    *      Release a reference to the specified object,
    *      gained either through a vm_object_allocate
    *      or a vm_object_reference call.  When all references
    *      are gone, storage associated with this object
    *      may be relinquished.
    *
    *      No object may be locked.
    */
   void
   vm_object_deallocate(object)
           vm_object_t object;
   {
           vm_object_t temp;
   
           while (object != NULL) {
   
                   if (object->type == OBJT_VNODE) {
                           vm_object_vndeallocate(object);
                           return;
                   }
   
                   if (object->ref_count == 0) {
                           panic("vm_object_deallocate: object deallocated too many times: %d", object->type);
                   } else if (object->ref_count > 2) {
                           object->ref_count--;
                           return;
                   }
   
                   /*
                    * Here on ref_count of one or two, which are special cases for
                    * objects.
                    */
                   if ((object->ref_count == 2) && (object->shadow_count == 0)) {
                           vm_object_set_flag(object, OBJ_ONEMAPPING);
                           object->ref_count--;
                           return;
                   } else if ((object->ref_count == 2) && (object->shadow_count == 1)) {
                           object->ref_count--;
                           if ((object->handle == NULL) &&
                               (object->type == OBJT_DEFAULT ||
                                object->type == OBJT_SWAP)) {
                                   vm_object_t robject;
   
                                   robject = TAILQ_FIRST(&object->shadow_head);
                                   KASSERT(robject != NULL,
                                       ("vm_object_deallocate: ref_count: %d, shadow_count: %d",
                                            object->ref_count,
                                            object->shadow_count));
                                   if ((robject->handle == NULL) &&
                                       (robject->type == OBJT_DEFAULT ||
                                        robject->type == OBJT_SWAP)) {
   
                                           robject->ref_count++;
   
                           retry:
                                           if (robject->paging_in_progress ||
                                                           object->paging_in_progress) {
                                                   vm_object_pip_sleep(robject, "objde1");
                                                   if (robject->paging_in_progress &&
                                                           robject->type == OBJT_SWAP) {
                                                           swap_pager_sync();
                                                           goto retry;
                                                   }
   
                                                   vm_object_pip_sleep(object, "objde2");
                                                   if (object->paging_in_progress &&
                                                           object->type == OBJT_SWAP) {
                                                           swap_pager_sync();
                                                   }
                                                   goto retry;
                                           }
   
                                           if( robject->ref_count == 1) {
                                                   robject->ref_count--;
                                                   object = robject;
                                                   goto doterm;
                                           }
   
                                           object = robject;
                                           vm_object_collapse(object);
                                           continue;
                                   }
                           }
   
                           return;
   
                   } else {
                           object->ref_count--;
                           if (object->ref_count != 0)
                                   return;
                   }
   
   doterm:
   
                   temp = object->backing_object;
                   if (temp) {
                           TAILQ_REMOVE(&temp->shadow_head, object, shadow_list);
                           temp->shadow_count--;
                           if (temp->ref_count == 0)
                                   vm_object_clear_flag(temp, OBJ_OPT);
                           temp->generation++;
                           object->backing_object = NULL;
                   }
                   vm_object_terminate(object);
                   /* unlocks and deallocates object */
                   object = temp;
           }
   }
   
   /*
    *      vm_object_terminate actually destroys the specified object, freeing
    *      up all previously used resources.
    *
    *      The object must be locked.
    */
   void
   vm_object_terminate(object)
           register vm_object_t object;
   {
           register vm_page_t p;
           int s;
   
           /*
            * Make sure no one uses us.
            */
           vm_object_set_flag(object, OBJ_DEAD);
   
           /*
            * wait for the pageout daemon to be done with the object
            */
           vm_object_pip_wait(object, "objtrm");
   
           KASSERT(!object->paging_in_progress,
                   ("vm_object_terminate: pageout in progress"));
   
           /*
            * Clean and free the pages, as appropriate. All references to the
            * object are gone, so we don't need to lock it.
            */
           if (object->type == OBJT_VNODE) {
                   struct vnode *vp;
   
                   /*
                    * Freeze optimized copies.
                    */
                   vm_freeze_copyopts(object, 0, object->size);
   
                   /*
                    * Clean pages and flush buffers.
                    */
                   vm_object_page_clean(object, 0, 0, OBJPC_SYNC);
   
                   vp = (struct vnode *) object->handle;
                   vinvalbuf(vp, V_SAVE, NOCRED, NULL, 0, 0);
           }
   
           if (object->ref_count != 0)
                   panic("vm_object_terminate: object with references, ref_count=%d", object->ref_count);
   
           /*
            * Now free any remaining pages. For internal objects, this also
            * removes them from paging queues. Don't free wired pages, just
            * remove them from the object.
            */
           s = splvm();
           while ((p = TAILQ_FIRST(&object->memq)) != NULL) {
   #if !defined(MAX_PERF)
                   if (p->busy || (p->flags & PG_BUSY))
                           printf("vm_object_terminate: freeing busy page\n");
   #endif
                   if (p->wire_count == 0) {
                           vm_page_busy(p);
                           vm_page_free(p);
                           cnt.v_pfree++;
                   } else {
                           vm_page_busy(p);
                           vm_page_remove(p);
                   }
           }
           splx(s);
   
           /*
            * Let the pager know object is dead.
            */
           vm_pager_deallocate(object);
   
           /*
            * Remove the object from the global object list.
            */
           simple_lock(&vm_object_list_lock);
           TAILQ_REMOVE(&vm_object_list, object, object_list);
           simple_unlock(&vm_object_list_lock);
   
           wakeup(object);
   
           /*
            * Free the space for the object.
            */
           zfree(obj_zone, object);
   }
   
   /*
    *      vm_object_page_clean
    *
    *      Clean all dirty pages in the specified range of object.
    *      Leaves page on whatever queue it is currently on.
    *
    *      Odd semantics: if start == end, we clean everything.
    *
    *      The object must be locked.
    */
   
   void
   vm_object_page_clean(object, start, end, flags)
           vm_object_t object;
           vm_pindex_t start;
           vm_pindex_t end;
           int flags;
   {
           register vm_page_t p, np, tp;
           register vm_offset_t tstart, tend;
           vm_pindex_t pi;
           int s;
           struct vnode *vp;
           int runlen;
           int maxf;
           int chkb;
           int maxb;
           int i;
           int pagerflags;
           vm_page_t maf[vm_pageout_page_count];
           vm_page_t mab[vm_pageout_page_count];
           vm_page_t ma[vm_pageout_page_count];
           int curgeneration;
   
           if (object->type != OBJT_VNODE ||
                   (object->flags & OBJ_MIGHTBEDIRTY) == 0)
                   return;
   
           pagerflags = (flags & (OBJPC_SYNC | OBJPC_INVAL)) ? VM_PAGER_PUT_SYNC : 0;
           pagerflags |= (flags & OBJPC_INVAL) ? VM_PAGER_PUT_INVAL : 0;
   
           vp = object->handle;
   
           vm_object_set_flag(object, OBJ_CLEANING);
   
           tstart = start;
           if (end == 0) {
                   tend = object->size;
           } else {
                   tend = end;
           }
   
           for(p = TAILQ_FIRST(&object->memq); p; p = TAILQ_NEXT(p, listq)) {
                   vm_page_flag_set(p, PG_CLEANCHK);
                   vm_page_protect(p, VM_PROT_READ);
           }
   
           if ((tstart == 0) && (tend == object->size)) {
                   vm_object_clear_flag(object, OBJ_WRITEABLE|OBJ_MIGHTBEDIRTY);
           }
   
   rescan:
           curgeneration = object->generation;
   
           for(p = TAILQ_FIRST(&object->memq); p; p = np) {
                   np = TAILQ_NEXT(p, listq);
   
                   pi = p->pindex;
                   if (((p->flags & PG_CLEANCHK) == 0) ||
                           (pi < tstart) || (pi >= tend) ||
                           (p->valid == 0) ||
                           ((p->queue - p->pc) == PQ_CACHE)) {
                           vm_page_flag_clear(p, PG_CLEANCHK);
                           continue;
                   }
   
                   vm_page_test_dirty(p);
                   if ((p->dirty & p->valid) == 0) {
                           vm_page_flag_clear(p, PG_CLEANCHK);
                           continue;
                   }
   
                   s = splvm();
                   while ((p->flags & PG_BUSY) || p->busy) {
                           vm_page_flag_set(p, PG_WANTED | PG_REFERENCED);
                           tsleep(p, PVM, "vpcwai", 0);
                           if (object->generation != curgeneration) {
                                   splx(s);
                                   goto rescan;
                           }
                   }
   
                   maxf = 0;
                   for(i=1;i<vm_pageout_page_count;i++) {
                           if (tp = vm_page_lookup(object, pi + i)) {
                                   if ((tp->flags & PG_BUSY) ||
                                           (tp->flags & PG_CLEANCHK) == 0 ||
                                           (tp->busy != 0))
                                           break;
                                   if((tp->queue - tp->pc) == PQ_CACHE) {
                                           vm_page_flag_clear(tp, PG_CLEANCHK);
                                           break;
                                   }
                                   vm_page_test_dirty(tp);
                                   if ((tp->dirty & tp->valid) == 0) {
                                           vm_page_flag_clear(tp, PG_CLEANCHK);
                                           break;
                                   }
                                   maf[ i - 1 ] = tp;
                                   maxf++;
                                   continue;
                           }
                           break;
                   }
   
                   maxb = 0;
                   chkb = vm_pageout_page_count -  maxf;
                   if (chkb) {
                           for(i = 1; i < chkb;i++) {
                                   if (tp = vm_page_lookup(object, pi - i)) {
                                           if ((tp->flags & PG_BUSY) ||
                                                   (tp->flags & PG_CLEANCHK) == 0 ||
                                                   (tp->busy != 0))
                                                   break;
                                           if((tp->queue - tp->pc) == PQ_CACHE) {
                                                   vm_page_flag_clear(tp, PG_CLEANCHK);
                                                   break;
                                           }
                                           vm_page_test_dirty(tp);
                                           if ((tp->dirty & tp->valid) == 0) {
                                                   vm_page_flag_clear(tp, PG_CLEANCHK);
                                                   break;
                                           }
                                           mab[ i - 1 ] = tp;
                                           maxb++;
                                           continue;
                                   }
                                   break;
                           }
                   }
   
                   for(i=0;i<maxb;i++) {
                           int index = (maxb - i) - 1;
                           ma[index] = mab[i];
                           vm_page_flag_clear(ma[index], PG_CLEANCHK);
                   }
                   vm_page_flag_clear(p, PG_CLEANCHK);
                   ma[maxb] = p;
                   for(i=0;i<maxf;i++) {
                           int index = (maxb + i) + 1;
                           ma[index] = maf[i];
                           vm_page_flag_clear(ma[index], PG_CLEANCHK);
                   }
                   runlen = maxb + maxf + 1;
   
                   splx(s);
                   vm_pageout_flush(ma, runlen, pagerflags);
                   for (i = 0; i<runlen; i++) {
                           if (ma[i]->valid & ma[i]->dirty) {
                                   vm_page_protect(ma[i], VM_PROT_READ);
                                   vm_page_flag_set(ma[i], PG_CLEANCHK);
                           }
                   }
                   if (object->generation != curgeneration)
                           goto rescan;
           }
   
           VOP_FSYNC(vp, NULL, (pagerflags & VM_PAGER_PUT_SYNC)?MNT_WAIT:0, curproc);
   
           vm_object_clear_flag(object, OBJ_CLEANING);
           return;
   }
   
   #ifdef not_used
   /* XXX I cannot tell if this should be an exported symbol */
   /*
    *      vm_object_deactivate_pages
    *
    *      Deactivate all pages in the specified object.  (Keep its pages
    *      in memory even though it is no longer referenced.)
    *
    *      The object must be locked.
    */
   static void
   vm_object_deactivate_pages(object)
           register vm_object_t object;
   {
           register vm_page_t p, next;
   
           for (p = TAILQ_FIRST(&object->memq); p != NULL; p = next) {
                   next = TAILQ_NEXT(p, listq);
                   vm_page_deactivate(p);
           }
   }
   #endif
   
   /*
    *      vm_object_pmap_copy:
    *
    *      Makes all physical pages in the specified
    *      object range copy-on-write.  No writeable
    *      references to these pages should remain.
    *
    *      The object must *not* be locked.
    */
   void
   vm_object_pmap_copy(object, start, end)
           register vm_object_t object;
           register vm_pindex_t start;
           register vm_pindex_t end;
   {
           register vm_page_t p;
   
           if (object == NULL || (object->flags & OBJ_WRITEABLE) == 0)
                   return;
   
           for (p = TAILQ_FIRST(&object->memq);
                   p != NULL;
                   p = TAILQ_NEXT(p, listq)) {
                   vm_page_protect(p, VM_PROT_READ);
           }
   
           vm_object_clear_flag(object, OBJ_WRITEABLE);
   }
   
   /*
    * Same as vm_object_pmap_copy_1, except range checking really
    * works, and is meant for small sections of an object.
    */
   void
   vm_object_pmap_copy_1(object, start, end)
           register vm_object_t object;
           register vm_pindex_t start;
           register vm_pindex_t end;
   {
           vm_pindex_t idx;
           register vm_page_t p;
   
           if (object == NULL || (object->flags & OBJ_WRITEABLE) == 0)
                   return;
   
           for (idx = start; idx < end; idx++) {
                   p = vm_page_lookup(object, idx);
                   if (p == NULL)
                           continue;
                   vm_page_protect(p, VM_PROT_READ);
           }
   }
   
   /*
    *      vm_object_pmap_remove:
    *
    *      Removes all physical pages in the specified
    *      object range from all physical maps.
    *
    *      The object must *not* be locked.
    */
   void
   vm_object_pmap_remove(object, start, end)
           register vm_object_t object;
           register vm_pindex_t start;
           register vm_pindex_t end;
   {
           register vm_page_t p;
           if (object == NULL)
                   return;
           for (p = TAILQ_FIRST(&object->memq);
                   p != NULL;
                   p = TAILQ_NEXT(p, listq)) {
                   if (p->pindex >= start && p->pindex < end)
                           vm_page_protect(p, VM_PROT_NONE);
           }
           if ((start == 0) && (object->size == end))
                   vm_object_clear_flag(object, OBJ_WRITEABLE);
   }
   
   /*
    *      vm_object_madvise:
    *
    *      Implements the madvise function at the object/page level.
    */
   void
   vm_object_madvise(object, pindex, count, advise)
           vm_object_t object;
           vm_pindex_t pindex;
           int count;
           int advise;
   {
           vm_pindex_t end, tpindex;
           vm_object_t tobject;
           vm_page_t m;
   
           if (object == NULL)
                   return;
   
           end = pindex + count;
   
           for (; pindex < end; pindex += 1) {
   
   relookup:
                   tobject = object;
                   tpindex = pindex;
   shadowlookup:
                   if (tobject->type != OBJT_DEFAULT &&
                       tobject->type != OBJT_SWAP
                   ) {
                           continue;
                   }
   
                   if ((tobject->flags & OBJ_ONEMAPPING) == 0)
                           continue;
   
                   m = vm_page_lookup(tobject, tpindex);
   
                   if (m == NULL) {
                           tobject = tobject->backing_object;
                           if (tobject == NULL)
                                   continue;
   
                           tpindex += OFF_TO_IDX(tobject->backing_object_offset);
                           goto shadowlookup;
                   }
   
                   /*
                    * If the page is busy or not in a normal active state,
                    * we skip it.  Things can break if we mess with pages
                    * in any of the below states.
                    */
                   if (
                       m->hold_count || 
                       m->wire_count ||
                       m->valid != VM_PAGE_BITS_ALL
                   ) {
                           continue;
                   }
   
                   if (vm_page_sleep(m, "madvpo", &m->busy))
                           goto relookup;
   
                   if (advise == MADV_WILLNEED) {
                           vm_page_activate(m);
                   } else if (advise == MADV_DONTNEED) {
                           vm_page_deactivate(m);
                   } else if (advise == MADV_FREE) {
                           pmap_clear_modify(VM_PAGE_TO_PHYS(m));
                           m->dirty = 0;
                           /*
                            * Force a demand zero if attempt to read from swap.
                            * We currently don't handle vnode files correctly,
                            * and will reread stale contents unnecessarily.
                            */
                           if (object->type == OBJT_SWAP)
                                   swap_pager_dmzspace(tobject, m->pindex, 1);
                   }
           }       
   }
   
   /*
    *      vm_object_shadow:
    *
    *      Create a new object which is backed by the
    *      specified existing object range.  The source
    *      object reference is deallocated.
    *
    *      The new object and offset into that object
    *      are returned in the source parameters.
    */
   
   void
   vm_object_shadow(object, offset, length)
           vm_object_t *object;    /* IN/OUT */
           vm_ooffset_t *offset;   /* IN/OUT */
           vm_size_t length;
   {
           register vm_object_t source;
           register vm_object_t result;
   
           source = *object;
   
           /*
            * Allocate a new object with the given length
            */
   
           if ((result = vm_object_allocate(OBJT_DEFAULT, length)) == NULL)
                   panic("vm_object_shadow: no object for shadowing");
   
           /*
            * The new object shadows the source object, adding a reference to it.
            * Our caller changes his reference to point to the new object,
            * removing a reference to the source object.  Net result: no change
            * of reference count.
            *
            * Try to optimize the result object's page color when shadowing
            * in order to maintain page coloring consistancy in the combined 
            * shadowed object.
            */
           result->backing_object = source;
           if (source) {
                   TAILQ_INSERT_TAIL(&source->shadow_head, result, shadow_list);
                   vm_object_clear_flag(source, OBJ_ONEMAPPING);
                   source->shadow_count++;
                   source->generation++;
                   result->pg_color = (source->pg_color + OFF_TO_IDX(*offset)) & PQ_L2_MASK;
           }
   
           /*
            * Store the offset into the source object, and fix up the offset into
            * the new object.
            */
   
           result->backing_object_offset = *offset;
   
           /*
            * Return the new things
            */
   
           *offset = 0;
           *object = result;
   }
   
   
   /*
    * this version of collapse allows the operation to occur earlier and
    * when paging_in_progress is true for an object...  This is not a complete
    * operation, but should plug 99.9% of the rest of the leaks.
    */
   static void
   vm_object_qcollapse(object)
           register vm_object_t object;
   {
           register vm_object_t backing_object;
           register vm_pindex_t backing_offset_index, paging_offset_index;
           vm_pindex_t backing_object_paging_offset_index;
           vm_pindex_t new_pindex;
           register vm_page_t p, pp;
           register vm_size_t size;
   
           backing_object = object->backing_object;
           if (backing_object->ref_count != 1)
                   return;
   
           backing_object->ref_count += 2;
   
           backing_offset_index = OFF_TO_IDX(object->backing_object_offset);
           backing_object_paging_offset_index = OFF_TO_IDX(backing_object->paging_offset);
           paging_offset_index = OFF_TO_IDX(object->paging_offset);
           size = object->size;
           p = TAILQ_FIRST(&backing_object->memq);
           while (p) {
                   vm_page_t next;
   
                   next = TAILQ_NEXT(p, listq);
                   if ((p->flags & (PG_BUSY | PG_FICTITIOUS)) ||
                       !p->valid || p->hold_count || p->wire_count || p->busy) {
                           p = next;
                           continue;
                   }
                   vm_page_busy(p);
   
                   new_pindex = p->pindex - backing_offset_index;
                   if (p->pindex < backing_offset_index ||
                       new_pindex >= size) {
                           if (backing_object->type == OBJT_SWAP)
                                   swap_pager_freespace(backing_object,
                                       backing_object_paging_offset_index+p->pindex,
                                       1);
                           vm_page_protect(p, VM_PROT_NONE);
                           vm_page_free(p);
                   } else {
                           pp = vm_page_lookup(object, new_pindex);
                           if (pp != NULL ||
                                   (object->type == OBJT_SWAP && vm_pager_has_page(object,
                                       paging_offset_index + new_pindex, NULL, NULL))) {
                                   if (backing_object->type == OBJT_SWAP)
                                           swap_pager_freespace(backing_object,
                                               backing_object_paging_offset_index + p->pindex, 1);
                                   vm_page_protect(p, VM_PROT_NONE);
                                   vm_page_free(p);
                           } else {
                                   if (backing_object->type == OBJT_SWAP)
                                           swap_pager_freespace(backing_object,
                                               backing_object_paging_offset_index + p->pindex, 1);
   
                                   if ((p->queue - p->pc) == PQ_CACHE)
                                           vm_page_deactivate(p);
                                   else
                                           vm_page_protect(p, VM_PROT_NONE);
   
                                   vm_page_rename(p, object, new_pindex);
                                   p->dirty = VM_PAGE_BITS_ALL;
                           }
                   }
                   p = next;
           }
           backing_object->ref_count -= 2;
   }
   
   /*
    *      vm_object_collapse:
    *
    *      Collapse an object with the object backing it.
    *      Pages in the backing object are moved into the
    *      parent, and the backing object is deallocated.
    */
   void
   vm_object_collapse(object)
           vm_object_t object;
   
   {
           vm_object_t backing_object;
           vm_ooffset_t backing_offset;
           vm_size_t size;
           vm_pindex_t new_pindex, backing_offset_index;
           vm_page_t p, pp;
   
           while (TRUE) {
                  /*
                   * Verify that the conditions are right for collapse:
                   *
                   * The object exists and no pages in it are currently being paged
                   * out.
                   */
                  if (object == NULL)
                          return;
  
                  /*
                   * Make sure there is a backing object.
                   */
                  if ((backing_object = object->backing_object) == NULL)
                          return;
  
                  /*
                   * we check the backing object first, because it is most likely
                   * not collapsable.
                   */
                  if (backing_object->handle != NULL ||
                      (backing_object->type != OBJT_DEFAULT &&
                       backing_object->type != OBJT_SWAP) ||
                      (backing_object->flags & OBJ_DEAD) ||
                      object->handle != NULL ||
                      (object->type != OBJT_DEFAULT &&
                       object->type != OBJT_SWAP) ||
                      (object->flags & OBJ_DEAD)) {
                          return;
                  }
  
                  if (object->paging_in_progress != 0 ||
                      backing_object->paging_in_progress != 0) {
                          vm_object_qcollapse(object);
                          return;
                  }
  
                  /*
                   * We know that we can either collapse the backing object (if
                   * the parent is the only reference to it) or (perhaps) remove
                   * the parent's reference to it.
                   */
  
                  backing_offset = object->backing_object_offset;
                  backing_offset_index = OFF_TO_IDX(backing_offset);
                  size = object->size;
  
                  /*
                   * If there is exactly one reference to the backing object, we
                   * can collapse it into the parent.
                   */
  
                  if (backing_object->ref_count == 1) {
  
                          vm_object_set_flag(backing_object, OBJ_DEAD);
                          /*
                           * We can collapse the backing object.
                           *
                           * Move all in-memory pages from backing_object to the
                           * parent.  Pages that have been paged out will be
                           * overwritten by any of the parent's pages that
                           * shadow them.
                           */
  
                          while ((p = TAILQ_FIRST(&backing_object->memq)) != 0) {
                                  if (vm_page_sleep(p, "vmocol", &p->busy))
                                          continue;
                                  vm_page_busy(p);
                                  new_pindex = p->pindex - backing_offset_index;
  
                                  /*
                                   * If the parent has a page here, or if this
                                   * page falls outside the parent, dispose of
                                   * it.
                                   *
                                   * Otherwise, move it as planned.
                                   */
  
                                  if (p->pindex < backing_offset_index ||
                                      new_pindex >= size) {
                                          vm_page_protect(p, VM_PROT_NONE);
                                          vm_page_free(p);
                                  } else {
                                          pp = vm_page_lookup(object, new_pindex);
                                          if (pp != NULL || (object->type == OBJT_SWAP && vm_pager_has_page(object,
                                              OFF_TO_IDX(object->paging_offset) + new_pindex, NULL, NULL))) {
                                                  vm_page_protect(p, VM_PROT_NONE);
                                                  vm_page_free(p);
                                          } else {
                                                  if ((p->queue - p->pc) == PQ_CACHE)
                                                          vm_page_deactivate(p);
                                                  else
                                                          vm_page_protect(p, VM_PROT_NONE);
                                                  vm_page_rename(p, object, new_pindex);
                                                  p->dirty = VM_PAGE_BITS_ALL;
                                          }
                                  }
                          }
  
                          /*
                           * Move the pager from backing_object to object.
                           */
  
                          if (backing_object->type == OBJT_SWAP) {
                                  vm_object_pip_add(backing_object, 1);
                                  if (object->type == OBJT_SWAP) {
                                          vm_object_pip_add(object, 1);
                                          /*
                                           * copy shadow object pages into ours
                                           * and destroy unneeded pages in
                                           * shadow object.
                                           */
                                          swap_pager_copy(
                                              backing_object,
                                              OFF_TO_IDX(backing_object->paging_offset),
                                              object,
                                              OFF_TO_IDX(object->paging_offset),
                                              OFF_TO_IDX(object->backing_object_offset), TRUE);
                                          vm_object_pip_wakeup(object);
                                  } else {
                                          vm_object_pip_add(object, 1);
                                          /*
                                           * move the shadow backing_object's pager data to
                                           * "object" and convert "object" type to OBJT_SWAP.
                                           */
                                          object->type = OBJT_SWAP;
                                          object->un_pager.swp.swp_nblocks =
                                              backing_object->un_pager.swp.swp_nblocks;
                                          object->un_pager.swp.swp_allocsize =
                                              backing_object->un_pager.swp.swp_allocsize;
                                          object->un_pager.swp.swp_blocks =
                                              backing_object->un_pager.swp.swp_blocks;
                                          object->un_pager.swp.swp_poip =         /* XXX */
                                              backing_object->un_pager.swp.swp_poip;
                                          object->paging_offset = backing_object->paging_offset + backing_offset;
                                          TAILQ_INSERT_TAIL(&swap_pager_un_object_list, object, pager_object_list);
  
                                          /*
                                           * Convert backing object from OBJT_SWAP to
                                           * OBJT_DEFAULT. XXX - only the TAILQ_REMOVE is
                                           * actually necessary.
                                           */
                                          backing_object->type = OBJT_DEFAULT;
                                          TAILQ_REMOVE(&swap_pager_un_object_list, backing_object, pager_object_list);
                                          /*
                                           * free unnecessary blocks
                                           */
                                          swap_pager_freespace(object, 0,
                                                  OFF_TO_IDX(object->paging_offset));
                                          vm_object_pip_wakeup(object);
                                  }
  
                                  vm_object_pip_wakeup(backing_object);
                          }
                          /*
                           * Object now shadows whatever backing_object did.
                           * Note that the reference to backing_object->backing_object
                           * moves from within backing_object to within object.
                           */
  
                          TAILQ_REMOVE(&object->backing_object->shadow_head, object,
                              shadow_list);
                          object->backing_object->shadow_count--;
                          object->backing_object->generation++;
                          if (backing_object->backing_object) {
                                  TAILQ_REMOVE(&backing_object->backing_object->shadow_head,
                                      backing_object, shadow_list);
                                  backing_object->backing_object->shadow_count--;
                                  backing_object->backing_object->generation++;
                          }
                          object->backing_object = backing_object->backing_object;
                          if (object->backing_object) {
                                  TAILQ_INSERT_TAIL(&object->backing_object->shadow_head,
                                      object, shadow_list);
                                  object->backing_object->shadow_count++;
                                  object->backing_object->generation++;
                          }
  
                          object->backing_object_offset += backing_object->backing_object_offset;
                          /*
                           * Discard backing_object.
                           *
                           * Since the backing object has no pages, no pager left,
                           * and no object references within it, all that is
                           * necessary is to dispose of it.
                           */
  
                          TAILQ_REMOVE(&vm_object_list, backing_object,
                              object_list);
                          vm_object_count--;
  
                          zfree(obj_zone, backing_object);
  
                          object_collapses++;
                  } else {
                          vm_object_t new_backing_object;
                          /*
                           * If all of the pages in the backing object are
                           * shadowed by the parent object, the parent object no
                           * longer has to shadow the backing object; it can
                           * shadow the next one in the chain.
                           *
                           * The backing object must not be paged out - we'd have
                           * to check all of the paged-out pages, as well.
                           */
  
                          if (backing_object->type != OBJT_DEFAULT) {
                                  return;
                          }
                          /*
                           * Should have a check for a 'small' number of pages
                           * here.
                           */
  
                          for (p = TAILQ_FIRST(&backing_object->memq); p;
                                          p = TAILQ_NEXT(p, listq)) {
  
                                  new_pindex = p->pindex - backing_offset_index;
                                  vm_page_busy(p);
  
                                  /*
                                   * If the parent has a page here, or if this
                                   * page falls outside the parent, keep going.
                                   *
                                   * Otherwise, the backing_object must be left in
                                   * the chain.
                                   */
  
                                  if (p->pindex >= backing_offset_index &&
                                          new_pindex <= size) {
  
                                          pp = vm_page_lookup(object, new_pindex);
  
                                          if ((pp == NULL) || (pp->flags & PG_BUSY) || pp->busy) {
                                                  vm_page_wakeup(p);
                                                  return;
                                          }
  
                                          vm_page_busy(pp);
                                          if ((pp->valid == 0) &&
                                              !vm_pager_has_page(object, OFF_TO_IDX(object->paging_offset) + new_pindex, NULL, NULL)) {
                                                  /*
                                                   * Page still needed. Can't go any
                                                   * further.
                                                   */
                                                  vm_page_wakeup(pp);
                                                  vm_page_wakeup(p);
                                                  return;
                                          }
                                          vm_page_wakeup(pp);
                                  }
                                  vm_page_wakeup(p);
                          }
  
                          /*
                           * Make the parent shadow the next object in the
                           * chain.  Deallocating backing_object will not remove
                           * it, since its reference count is at least 2.
                           */
  
                          TAILQ_REMOVE(&backing_object->shadow_head,
                              object, shadow_list);
                          backing_object->shadow_count--;
                          backing_object->generation++;
  
                          new_backing_object = backing_object->backing_object;
                          if (object->backing_object = new_backing_object) {
                                  vm_object_reference(new_backing_object);
                                  TAILQ_INSERT_TAIL(&new_backing_object->shadow_head,
                                      object, shadow_list);
                                  new_backing_object->shadow_count++;
                                  new_backing_object->generation++;
                                  object->backing_object_offset +=
                                          backing_object->backing_object_offset;
                          }
  
                          /*
                           * Drop the reference count on backing_object. Since
                           * its ref_count was at least 2, it will not vanish;
                           * so we don't need to call vm_object_deallocate, but
                           * we do anyway.
                           */
                          vm_object_deallocate(backing_object);
                          object_bypasses++;
                  }
  
                  /*
                   * Try again with this object's new backing object.
                   */
          }
  }
  
  /*
   *      vm_object_page_remove: [internal]
   *
   *      Removes all physical pages in the specified
   *      object range from the object's list of pages.
   *
   *      The object must be locked.
   */
  void
  vm_object_page_remove(object, start, end, clean_only)
          register vm_object_t object;
          register vm_pindex_t start;
          register vm_pindex_t end;
          boolean_t clean_only;
  {
          register vm_page_t p, next;
          unsigned int size;
          int all;
  
          if (object == NULL ||
              object->resident_page_count == 0)
                  return;
  
          all = ((end == 0) && (start == 0));
  
          vm_object_pip_add(object, 1);
  again:
          size = end - start;
          if (all || size > object->resident_page_count / 4) {
                  for (p = TAILQ_FIRST(&object->memq); p != NULL; p = next) {
                          next = TAILQ_NEXT(p, listq);
                          if (all || ((start <= p->pindex) && (p->pindex < end))) {
                                  if (p->wire_count != 0) {
                                          vm_page_protect(p, VM_PROT_NONE);
                                          if (!clean_only)
                                                  p->valid = 0;
                                          continue;
                                  }
  
                                  /*
                                   * The busy flags are only cleared at
                                   * interrupt -- minimize the spl transitions
                                   */
  
                                  if (vm_page_sleep(p, "vmopar", &p->busy))
                                          goto again;
  
                                  if (clean_only && p->valid) {
                                          vm_page_test_dirty(p);
                                          if (p->valid & p->dirty)
                                                  continue;
                                  }
  
                                  vm_page_busy(p);
                                  vm_page_protect(p, VM_PROT_NONE);
                                  vm_page_free(p);
                          }
                  }
          } else {
                  while (size > 0) {
                          if ((p = vm_page_lookup(object, start)) != 0) {
  
                                  if (p->wire_count != 0) {
                                          vm_page_protect(p, VM_PROT_NONE);
                                          if (!clean_only)
                                                  p->valid = 0;
                                          start += 1;
                                          size -= 1;
                                          continue;
                                  }
  
                                  /*
                                   * The busy flags are only cleared at
                                   * interrupt -- minimize the spl transitions
                                   */
                                  if (vm_page_sleep(p, "vmopar", &p->busy))
                                          goto again;
  
                                  if (clean_only && p->valid) {
                                          vm_page_test_dirty(p);
                                          if (p->valid & p->dirty) {
                                                  start += 1;
                                                  size -= 1;
                                                  continue;
                                          }
                                  }
  
                                  vm_page_busy(p);
                                  vm_page_protect(p, VM_PROT_NONE);
                                  vm_page_free(p);
                          }
                          start += 1;
                          size -= 1;
                  }
          }
          vm_object_pip_wakeup(object);
  }
  
  /*
   *      Routine:        vm_object_coalesce
   *      Function:       Coalesces two objects backing up adjoining
   *                      regions of memory into a single object.
   *
   *      returns TRUE if objects were combined.
   *
   *      NOTE:   Only works at the moment if the second object is NULL -
   *              if it's not, which object do we lock first?
   *
   *      Parameters:
   *              prev_object     First object to coalesce
   *              prev_offset     Offset into prev_object
   *              next_object     Second object into coalesce
   *              next_offset     Offset into next_object
   *
   *              prev_size       Size of reference to prev_object
   *              next_size       Size of reference to next_object
   *
   *      Conditions:
   *      The object must *not* be locked.
   */
  boolean_t
  vm_object_coalesce(prev_object, prev_pindex, prev_size, next_size)
          register vm_object_t prev_object;
          vm_pindex_t prev_pindex;
          vm_size_t prev_size, next_size;
  {
          vm_size_t newsize;
  
          if (prev_object == NULL) {
                  return (TRUE);
          }
  
          if (prev_object->type != OBJT_DEFAULT) {
                  return (FALSE);
          }
  
          /*
           * Try to collapse the object first
           */
          vm_object_collapse(prev_object);
  
          /*
           * Can't coalesce if: . more than one reference . paged out . shadows
           * another object . has a copy elsewhere (any of which mean that the
           * pages not mapped to prev_entry may be in use anyway)
           */
  
          if (prev_object->backing_object != NULL) {
                  return (FALSE);
          }
  
          prev_size >>= PAGE_SHIFT;
          next_size >>= PAGE_SHIFT;
  
          if ((prev_object->ref_count > 1) &&
              (prev_object->size != prev_pindex + prev_size)) {
                  return (FALSE);
          }
  
          /*
           * Remove any pages that may still be in the object from a previous
           * deallocation.
           */
  
          vm_object_page_remove(prev_object,
              prev_pindex + prev_size,
              prev_pindex + prev_size + next_size, FALSE);
  
          /*
           * Extend the object if necessary.
           */
          newsize = prev_pindex + prev_size + next_size;
          if (newsize > prev_object->size)
                  prev_object->size = newsize;
  
          return (TRUE);
  }
  
  #include "opt_ddb.h"
  #ifdef DDB
  #include <sys/kernel.h>
  
  #include <machine/cons.h>
  
  #include <ddb/ddb.h>
  
  static int      _vm_object_in_map __P((vm_map_t map, vm_object_t object,
                                         vm_map_entry_t entry));
  static int      vm_object_in_map __P((vm_object_t object));
  
  static int
  _vm_object_in_map(map, object, entry)
          vm_map_t map;
          vm_object_t object;
          vm_map_entry_t entry;
  {
          vm_map_t tmpm;
          vm_map_entry_t tmpe;
          vm_object_t obj;
          int entcount;
  
          if (map == 0)
                  return 0;
  
          if (entry == 0) {
                  tmpe = map->header.next;
                  entcount = map->nentries;
                  while (entcount-- && (tmpe != &map->header)) {
                          if( _vm_object_in_map(map, object, tmpe)) {
                                  return 1;
                          }
                          tmpe = tmpe->next;
                  }
          } else if (entry->eflags & (MAP_ENTRY_IS_A_MAP|MAP_ENTRY_IS_SUB_MAP)) {
                  tmpm = entry->object.share_map;
                  tmpe = tmpm->header.next;
                  entcount = tmpm->nentries;
                  while (entcount-- && tmpe != &tmpm->header) {
                          if( _vm_object_in_map(tmpm, object, tmpe)) {
                                  return 1;
                          }
                          tmpe = tmpe->next;
                  }
          } else if (obj = entry->object.vm_object) {
                  for(; obj; obj=obj->backing_object)
                          if( obj == object) {
                                  return 1;
                          }
          }
          return 0;
  }
  
  static int
  vm_object_in_map( object)
          vm_object_t object;
  {
          struct proc *p;
          for (p = allproc.lh_first; p != 0; p = p->p_list.le_next) {
                  if( !p->p_vmspace /* || (p->p_flag & (P_SYSTEM|P_WEXIT)) */)
                          continue;
                  if( _vm_object_in_map(&p->p_vmspace->vm_map, object, 0))
                          return 1;
          }
          if( _vm_object_in_map( kernel_map, object, 0))
                  return 1;
          if( _vm_object_in_map( kmem_map, object, 0))
                  return 1;
          if( _vm_object_in_map( pager_map, object, 0))
                  return 1;
          if( _vm_object_in_map( buffer_map, object, 0))
                  return 1;
          if( _vm_object_in_map( io_map, object, 0))
                  return 1;
          if( _vm_object_in_map( phys_map, object, 0))
                  return 1;
          if( _vm_object_in_map( mb_map, object, 0))
                  return 1;
          if( _vm_object_in_map( u_map, object, 0))
                  return 1;
          return 0;
  }
  
  DB_SHOW_COMMAND(vmochk, vm_object_check)
  {
          vm_object_t object;
  
          /*
           * make sure that internal objs are in a map somewhere
           * and none have zero ref counts.
           */
          for (object = TAILQ_FIRST(&vm_object_list);
                          object != NULL;
                          object = TAILQ_NEXT(object, object_list)) {
                  if (object->handle == NULL &&
                      (object->type == OBJT_DEFAULT || object->type == OBJT_SWAP)) {
                          if (object->ref_count == 0) {
                                  db_printf("vmochk: internal obj has zero ref count: %d\n",
                                          object->size);
                          }
                          if (!vm_object_in_map(object)) {
                                  db_printf(
                          "vmochk: internal obj is not in a map: "
                          "ref: %d, size: %lu: 0x%lx, backing_object: %p\n",
                                      object->ref_count, (u_long)object->size, 
                                      (u_long)object->size,
                                      (void *)object->backing_object);
                          }
                  }
          }
  }
  
  /*
   *      vm_object_print:        [ debug ]
   */
  DB_SHOW_COMMAND(object, vm_object_print_static)
  {
          /* XXX convert args. */
          vm_object_t object = (vm_object_t)addr;
          boolean_t full = have_addr;
  
          register vm_page_t p;
  
          /* XXX count is an (unused) arg.  Avoid shadowing it. */
  #define count   was_count
  
          register int count;
  
          if (object == NULL)
                  return;
  
          db_iprintf(
              "Object %p: type=%d, size=0x%lx, res=%d, ref=%d, flags=0x%x\n",
              object, (int)object->type, (u_long)object->size,
              object->resident_page_count, object->ref_count, object->flags);
          /*
           * XXX no %qd in kernel.  Truncate object->paging_offset and
           * object->backing_object_offset.
           */
          db_iprintf(" sref=%d, offset=0x%lx, backing_object(%d)=(%p)+0x%lx\n",
              object->shadow_count, (long)object->paging_offset,
              object->backing_object ? object->backing_object->ref_count : 0,
              object->backing_object, (long)object->backing_object_offset);
  
          if (!full)
                  return;
  
          db_indent += 2;
          count = 0;
          for (p = TAILQ_FIRST(&object->memq); p != NULL; p = TAILQ_NEXT(p, listq)) {
                  if (count == 0)
                          db_iprintf("memory:=");
                  else if (count == 6) {
                          db_printf("\n");
                          db_iprintf(" ...");
                          count = 0;
                  } else
                          db_printf(",");
                  count++;
  
                  db_printf("(off=0x%lx,page=0x%lx)",
                      (u_long) p->pindex, (u_long) VM_PAGE_TO_PHYS(p));
          }
          if (count != 0)
                  db_printf("\n");
          db_indent -= 2;
  }
  
  /* XXX. */
  #undef count
  
  /* XXX need this non-static entry for calling from vm_map_print. */
  void
  vm_object_print(addr, have_addr, count, modif)
          /* db_expr_t */ long addr;
          boolean_t have_addr;
          /* db_expr_t */ long count;
          char *modif;
  {
          vm_object_print_static(addr, have_addr, count, modif);
  }
  
  DB_SHOW_COMMAND(vmopag, vm_object_print_pages)
  {
          vm_object_t object;
          int nl = 0;
          int c;
          for (object = TAILQ_FIRST(&vm_object_list);
                          object != NULL;
                          object = TAILQ_NEXT(object, object_list)) {
                  vm_pindex_t idx, fidx;
                  vm_pindex_t osize;
                  vm_offset_t pa = -1, padiff;
                  int rcount;
                  vm_page_t m;
  
                  db_printf("new object: %p\n", (void *)object);
                  if ( nl > 18) {
                          c = cngetc();
                          if (c != ' ')
                                  return;
                          nl = 0;
                  }
                  nl++;
                  rcount = 0;
                  fidx = 0;
                  osize = object->size;
                  if (osize > 128)
                          osize = 128;
                  for(idx=0;idx<osize;idx++) {
                          m = vm_page_lookup(object, idx);
                          if (m == NULL) {
                                  if (rcount) {
                                          db_printf(" index(%d)run(%d)pa(0x%x)\n",
                                                  fidx, rcount, pa);
                                          if ( nl > 18) {
                                                  c = cngetc();
                                                  if (c != ' ')
                                                          return;
                                                  nl = 0;
                                          }
                                          nl++;
                                          rcount = 0;
                                  }
                                  continue;
                          }
  
                                  
                          if (rcount &&
                                  (VM_PAGE_TO_PHYS(m) == pa + rcount * PAGE_SIZE)) {
                                  ++rcount;
                                  continue;
                          }
                          if (rcount) {
                                  padiff = pa + rcount * PAGE_SIZE - VM_PAGE_TO_PHYS(m);
                                  padiff >>= PAGE_SHIFT;
                                  padiff &= PQ_L2_MASK;
                                  if (padiff == 0) {
                                          pa = VM_PAGE_TO_PHYS(m) - rcount * PAGE_SIZE;
                                          ++rcount;
                                          continue;
                                  }
                                  db_printf(" index(%d)run(%d)pa(0x%x)", fidx, rcount, pa);
                                  db_printf("pd(%d)\n", padiff);
                                  if ( nl > 18) {
                                          c = cngetc();
                                          if (c != ' ')
                                                  return;
                                          nl = 0;
                                  }
                                  nl++;
                          }
                          fidx = idx;
                          pa = VM_PAGE_TO_PHYS(m);
                          rcount = 1;
                  }
                  if (rcount) {
                          db_printf(" index(%d)run(%d)pa(0x%x)\n", fidx, rcount, pa);
                          if ( nl > 18) {
                                  c = cngetc();
                                  if (c != ' ')
                                          return;
                                  nl = 0;
                          }
                          nl++;
                  }
          }
  }
  #endif /* DDB */

Cache object: b8eff5e7ed48a654ab56124b1f05e082