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uvm_anon.h revision 1.4
      1 /*	$NetBSD: uvm_anon.h,v 1.4 1998/02/09 04:05:36 mrg Exp $	*/
      2 
      3 /*
      4  * XXXCDC: "ROUGH DRAFT" QUALITY UVM PRE-RELEASE FILE!
      5  *	   >>>USE AT YOUR OWN RISK, WORK IS NOT FINISHED<<<
      6  */
      7 /*
      8  *
      9  * Copyright (c) 1997 Charles D. Cranor and Washington University.
     10  * All rights reserved.
     11  *
     12  * Redistribution and use in source and binary forms, with or without
     13  * modification, are permitted provided that the following conditions
     14  * are met:
     15  * 1. Redistributions of source code must retain the above copyright
     16  *    notice, this list of conditions and the following disclaimer.
     17  * 2. Redistributions in binary form must reproduce the above copyright
     18  *    notice, this list of conditions and the following disclaimer in the
     19  *    documentation and/or other materials provided with the distribution.
     20  * 3. All advertising materials mentioning features or use of this software
     21  *    must display the following acknowledgement:
     22  *      This product includes software developed by Charles D. Cranor and
     23  *      Washington University.
     24  * 4. The name of the author may not be used to endorse or promote products
     25  *    derived from this software without specific prior written permission.
     26  *
     27  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     28  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     29  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     30  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     31  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     32  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     33  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     34  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     35  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     36  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     37  *
     38  * from: Id: uvm_anon.h,v 1.1.2.4 1998/01/04 22:43:39 chuck Exp
     39  */
     40 
     41 /*
     42  * uvm_anon.h
     43  */
     44 
     45 /*
     46  * anonymous memory management
     47  *
     48  * anonymous virtual memory is short term virtual memory that goes away
     49  * when the processes referencing it go away.    an anonymous page of
     50  * virtual memory is described by the following data structure:
     51  */
     52 
     53 struct vm_anon {
     54 	int an_ref;			/* reference count [an_lock] */
     55 #if NCPU > 1
     56 	simple_lock_data_t an_lock;	/* lock for an_ref */
     57 #endif
     58 	union {
     59 		struct vm_anon *an_nxt;	/* if on free list [afreelock] */
     60 		struct vm_page *an_page;/* if in RAM [pageqlock] */
     61 	} u;
     62 	int an_swslot;		/* drum swap slot # (if != 0) [pageqlock] */
     63 };
     64 
     65 /*
     66  * a pool of vm_anon data structures is allocated and put on a global
     67  * free list at boot time.  vm_anon's on the free list use "an_nxt" as
     68  * a pointer to the next item on the free list.  for active vm_anon's
     69  * the data can be in one of the following state: [1] in a vm_page
     70  * with no backing store allocated yet, [2] in a vm_page with backing
     71  * store allocated, or [3] paged out to backing store (no vm_page).
     72  *
     73  * for pageout in case [2]: if the page has been modified then we must
     74  * flush it out to backing store, otherwise we can just dump the
     75  * vm_page.
     76  */
     77 
     78 /*
     79  * anonymous virtual memory pages (vm_anon's) live in anonymous memory
     80  * maps.   anonymous memory maps can be shared between processes.
     81  * different subsets of an anonymous memory map can be referenced by
     82  * processes (see below).    an anonymous map is described by the following
     83  * data structure:
     84  */
     85 
     86 #define VM_AMAP_PPREF		/* use a per-page reference count for split
     87 				   vm_map_entry_t's. */
     88 
     89 struct vm_amap {
     90 #if NCPU > 1
     91 	simple_lock_data_t am_l; /* simple lock [locks all vm_amap fields] */
     92 #endif
     93 	int am_ref;		/* reference count */
     94 	int am_flags;		/* flags */
     95 	int am_maxslot;		/* max # of slots allocated */
     96 	int am_nslot;		/* # of slots currently in map ( <= maxslot) */
     97 	int am_nused;		/* # of slots currently in use */
     98 	int *am_slots;		/* contig array of active slots */
     99 	int *am_bckptr;		/* back pointer array to am_slots */
    100 	struct vm_anon **am_anon; /* array of anonymous pages */
    101 #ifdef VM_AMAP_PPREF
    102 	int *am_ppref;		/* per page reference count (if !NULL) */
    103 #endif
    104 };
    105 
    106 #define AMAP_SHARED	0x1	/* am_flags: shared amap */
    107 #define AMAP_REFALL	0x2	/* flag to amap_ref() */
    108 
    109 /*
    110  * note that am_slots, am_bckptr, and am_anon are arrays.   this allows
    111  * fast lookup of pages based on their virual address at the expense of
    112  * some extra memory.    [XXX: for memory starved systems provide alternate
    113  * functions?]
    114  *
    115  * 4 slot/page example, with slots 1 and 3 in use:
    116  * ("D/C" == don't care what the value is)
    117  *
    118  *            0     1      2     3
    119  * am_anon:   NULL, anon0, NULL, anon1		(actual pointers to anons)
    120  * am_bckptr: D/C,  1,     D/C,  0		(points to am_slots entry)
    121  *
    122  * am_slots:  3, 1, D/C, D/C    		(says slots 3 and 1 are in use)
    123  *
    124  * note that am_bckptr is D/C if the slot in am_anon is set to NULL.
    125  * to find the entry in am_slots for an anon, look at am_bckptr[slot],
    126  * thus the entry for slot 3 in am_slots[] is at am_slots[am_bckptr[3]].
    127  * in general, if am_anon[X] is non-NULL, then the following must be
    128  * true: am_slots[am_bckptr[X]] == X
    129  *
    130  * note that am_slots is always contig-packed.
    131  */
    132 
    133 /*
    134  * processes reference anonymous virtual memory maps with an anonymous
    135  * reference structure:
    136  */
    137 
    138 struct vm_aref {
    139 	int ar_slotoff;			/* slot offset into amap we start */
    140 	struct vm_amap *ar_amap;	/* pointer to amap */
    141 };
    142 
    143 /*
    144  * the offset field indicates which part of the amap we are referencing.
    145  * locked by vm_map lock.
    146  */
    147 
    148