/* $NetBSD: uvm_anon.h,v 1.7 1998/03/09 00:58:56 mrg 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 [pageqlock] */ } u; int an_swslot; /* drum swap slot # (if != 0) [pageqlock] */ }; /* * 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_ */