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uvm_anon.h revision 1.15 
      1 /*	$NetBSD: uvm_anon.h,v 1.15 2001/05/26 16:32:46 chs Exp $	*/
      2 
      3 /*
      4  *
      5  * Copyright (c) 1997 Charles D. Cranor and Washington University.
      6  * All rights reserved.
      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  * 3. All advertising materials mentioning features or use of this software
     17  *    must display the following acknowledgement:
     18  *      This product includes software developed by Charles D. Cranor and
     19  *      Washington University.
     20  * 4. The name of the author may not be used to endorse or promote products
     21  *    derived from this software without specific prior written permission.
     22  *
     23  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     24  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     25  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     26  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     27  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     28  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     29  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     30  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     31  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     32  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     33  */
     34 
     35 #ifndef _UVM_UVM_ANON_H_
     36 #define _UVM_UVM_ANON_H_
     37 
     38 /*
     39  * uvm_anon.h
     40  */
     41 
     42 /*
     43  * anonymous memory management
     44  *
     45  * anonymous virtual memory is short term virtual memory that goes away
     46  * when the processes referencing it go away.    an anonymous page of
     47  * virtual memory is described by the following data structure:
     48  */
     49 
     50 struct vm_anon {
     51 	int an_ref;			/* reference count [an_lock] */
     52 	struct simplelock an_lock;	/* lock for an_ref */
     53 	union {
     54 		struct vm_anon *an_nxt;	/* if on free list [afreelock] */
     55 		struct vm_page *an_page;/* if in RAM [an_lock] */
     56 	} u;
     57 	int an_swslot;		/* drum swap slot # (if != 0)
     58 				   [an_lock.  also, it is ok to read
     59 				   an_swslot if we hold an_page PG_BUSY] */
     60 };
     61 
     62 /*
     63  * a pool of vm_anon data structures is allocated and put on a global
     64  * free list at boot time.  vm_anon's on the free list use "an_nxt" as
     65  * a pointer to the next item on the free list.  for active vm_anon's
     66  * the data can be in one of the following state: [1] in a vm_page
     67  * with no backing store allocated yet, [2] in a vm_page with backing
     68  * store allocated, or [3] paged out to backing store (no vm_page).
     69  *
     70  * for pageout in case [2]: if the page has been modified then we must
     71  * flush it out to backing store, otherwise we can just dump the
     72  * vm_page.
     73  */
     74 
     75 /*
     76  * anons are grouped together in anonymous memory maps, or amaps.
     77  * amaps are defined in uvm_amap.h.
     78  */
     79 
     80 /*
     81  * processes reference anonymous virtual memory maps with an anonymous
     82  * reference structure:
     83  */
     84 
     85 struct vm_aref {
     86 	int ar_pageoff;			/* page offset into amap we start */
     87 	struct vm_amap *ar_amap;	/* pointer to amap */
     88 };
     89 
     90 /*
     91  * the offset field indicates which part of the amap we are referencing.
     92  * locked by vm_map lock.
     93  */
     94 
     95 #ifdef _KERNEL
     96 
     97 /*
     98  * prototypes
     99  */
    100 
    101 struct vm_anon *uvm_analloc __P((void));
    102 void uvm_anfree __P((struct vm_anon *));
    103 void uvm_anon_init __P((void));
    104 int uvm_anon_add __P((int));
    105 void uvm_anon_remove __P((int));
    106 struct vm_page *uvm_anon_lockloanpg __P((struct vm_anon *));
    107 void uvm_anon_dropswap __P((struct vm_anon *));
    108 boolean_t anon_swap_off __P((int, int));
    109 #endif /* _KERNEL */
    110 
    111 #endif /* _UVM_UVM_ANON_H_ */
    112