swap_pager.h revision 1542
1/* 2 * Copyright (c) 1990 University of Utah. 3 * Copyright (c) 1991, 1993 4 * The Regents of the University of California. All rights reserved. 5 * 6 * This code is derived from software contributed to Berkeley by 7 * the Systems Programming Group of the University of Utah Computer 8 * Science Department. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 * 38 * @(#)swap_pager.h 8.1 (Berkeley) 6/11/93 39 */ 40 41#ifndef _SWAP_PAGER_ 42#define _SWAP_PAGER_ 1 43 44/* 45 * In the swap pager, the backing store for an object is organized as an 46 * array of some number of "swap blocks". A swap block consists of a bitmask 47 * and some number of contiguous DEV_BSIZE disk blocks. The minimum size 48 * of a swap block is: 49 * 50 * max(PAGE_SIZE, dmmin*DEV_BSIZE) [ 32k currently ] 51 * 52 * bytes (since the pager interface is page oriented), the maximum size is: 53 * 54 * min(#bits(swb_mask)*PAGE_SIZE, dmmax*DEV_BSIZE) [ 128k currently ] 55 * 56 * where dmmin and dmmax are left over from the old VM interface. The bitmask 57 * (swb_mask) is used by swap_pager_haspage() to determine if a particular 58 * page has actually been written; i.e. the pager copy of the page is valid. 59 * All swap blocks in the backing store of an object will be the same size. 60 * 61 * The reason for variable sized swap blocks is to reduce fragmentation of 62 * swap resources. Whenever possible we allocate smaller swap blocks to 63 * smaller objects. The swap block size is determined from a table of 64 * object-size vs. swap-block-size computed at boot time. 65 */ 66typedef int sw_bm_t; /* pager bitmask */ 67 68struct swblock { 69 sw_bm_t swb_mask; /* bitmask of valid pages in this block */ 70 daddr_t swb_block; /* starting disk block for this block */ 71}; 72typedef struct swblock *sw_blk_t; 73 74/* 75 * Swap pager private data. 76 */ 77struct swpager { 78 vm_size_t sw_osize; /* size of object we are backing (bytes) */ 79 int sw_bsize; /* size of swap blocks (DEV_BSIZE units) */ 80 int sw_nblocks;/* number of blocks in list (sw_blk_t units) */ 81 sw_blk_t sw_blocks; /* pointer to list of swap blocks */ 82 short sw_flags; /* flags */ 83 short sw_poip; /* pageouts in progress */ 84}; 85typedef struct swpager *sw_pager_t; 86 87#define SW_WANTED 0x01 88#define SW_NAMED 0x02 89 90#endif /* _SWAP_PAGER_ */ 91