NetBSD/sys/uvm/uvm_anon.h

151 lines
5.5 KiB
C

/* $NetBSD: uvm_anon.h,v 1.8 1998/11/20 19:37:06 chuck Exp $ */
/*
* XXXCDC: "ROUGH DRAFT" QUALITY UVM PRE-RELEASE FILE!
* >>>USE AT YOUR OWN RISK, WORK IS NOT FINISHED<<<
*/
/*
*
* Copyright (c) 1997 Charles D. Cranor and Washington University.
* All rights reserved.
*
* 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 Charles D. Cranor and
* Washington University.
* 4. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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: Id: uvm_anon.h,v 1.1.2.4 1998/01/04 22:43:39 chuck Exp
*/
#ifndef _UVM_UVM_ANON_H_
#define _UVM_UVM_ANON_H_
/*
* uvm_anon.h
*/
/*
* anonymous memory management
*
* anonymous virtual memory is short term virtual memory that goes away
* when the processes referencing it go away. an anonymous page of
* virtual memory is described by the following data structure:
*/
struct vm_anon {
int an_ref; /* reference count [an_lock] */
simple_lock_data_t an_lock; /* lock for an_ref */
union {
struct vm_anon *an_nxt; /* if on free list [afreelock] */
struct vm_page *an_page;/* if in RAM [an_lock] */
} u;
int an_swslot; /* drum swap slot # (if != 0)
[an_lock. also, it is ok to read
an_swslot if we hold an_page PG_BUSY] */
};
/*
* a pool of vm_anon data structures is allocated and put on a global
* free list at boot time. vm_anon's on the free list use "an_nxt" as
* a pointer to the next item on the free list. for active vm_anon's
* the data can be in one of the following state: [1] in a vm_page
* with no backing store allocated yet, [2] in a vm_page with backing
* store allocated, or [3] paged out to backing store (no vm_page).
*
* for pageout in case [2]: if the page has been modified then we must
* flush it out to backing store, otherwise we can just dump the
* vm_page.
*/
/*
* anonymous virtual memory pages (vm_anon's) live in anonymous memory
* maps. anonymous memory maps can be shared between processes.
* different subsets of an anonymous memory map can be referenced by
* processes (see below). an anonymous map is described by the following
* data structure:
*/
#define VM_AMAP_PPREF /* use a per-page reference count for split
vm_map_entry_t's. */
struct vm_amap {
simple_lock_data_t am_l; /* simple lock [locks all vm_amap fields] */
int am_ref; /* reference count */
int am_flags; /* flags */
int am_maxslot; /* max # of slots allocated */
int am_nslot; /* # of slots currently in map ( <= maxslot) */
int am_nused; /* # of slots currently in use */
int *am_slots; /* contig array of active slots */
int *am_bckptr; /* back pointer array to am_slots */
struct vm_anon **am_anon; /* array of anonymous pages */
#ifdef VM_AMAP_PPREF
int *am_ppref; /* per page reference count (if !NULL) */
#endif
};
#define AMAP_SHARED 0x1 /* am_flags: shared amap */
#define AMAP_REFALL 0x2 /* flag to amap_ref() */
/*
* note that am_slots, am_bckptr, and am_anon are arrays. this allows
* fast lookup of pages based on their virual address at the expense of
* some extra memory. [XXX: for memory starved systems provide alternate
* functions?]
*
* 4 slot/page example, with slots 1 and 3 in use:
* ("D/C" == don't care what the value is)
*
* 0 1 2 3
* am_anon: NULL, anon0, NULL, anon1 (actual pointers to anons)
* am_bckptr: D/C, 1, D/C, 0 (points to am_slots entry)
*
* am_slots: 3, 1, D/C, D/C (says slots 3 and 1 are in use)
*
* note that am_bckptr is D/C if the slot in am_anon is set to NULL.
* to find the entry in am_slots for an anon, look at am_bckptr[slot],
* thus the entry for slot 3 in am_slots[] is at am_slots[am_bckptr[3]].
* in general, if am_anon[X] is non-NULL, then the following must be
* true: am_slots[am_bckptr[X]] == X
*
* note that am_slots is always contig-packed.
*/
/*
* processes reference anonymous virtual memory maps with an anonymous
* reference structure:
*/
struct vm_aref {
int ar_slotoff; /* slot offset into amap we start */
struct vm_amap *ar_amap; /* pointer to amap */
};
/*
* the offset field indicates which part of the amap we are referencing.
* locked by vm_map lock.
*/
#endif /* _UVM_UVM_ANON_H_ */