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 * %sccs.include.redist.c% 11 * 12 * @(#)swap_pager.h 8.1 (Berkeley) 06/11/93 13 */ 14 15 #ifndef _SWAP_PAGER_ 16 #define _SWAP_PAGER_ 1 17 18 /* 19 * In the swap pager, the backing store for an object is organized as an 20 * array of some number of "swap blocks". A swap block consists of a bitmask 21 * and some number of contiguous DEV_BSIZE disk blocks. The minimum size 22 * of a swap block is: 23 * 24 * max(PAGE_SIZE, dmmin*DEV_BSIZE) [ 32k currently ] 25 * 26 * bytes (since the pager interface is page oriented), the maximum size is: 27 * 28 * min(#bits(swb_mask)*PAGE_SIZE, dmmax*DEV_BSIZE) [ 128k currently ] 29 * 30 * where dmmin and dmmax are left over from the old VM interface. The bitmask 31 * (swb_mask) is used by swap_pager_haspage() to determine if a particular 32 * page has actually been written; i.e. the pager copy of the page is valid. 33 * All swap blocks in the backing store of an object will be the same size. 34 * 35 * The reason for variable sized swap blocks is to reduce fragmentation of 36 * swap resources. Whenever possible we allocate smaller swap blocks to 37 * smaller objects. The swap block size is determined from a table of 38 * object-size vs. swap-block-size computed at boot time. 39 */ 40 typedef int sw_bm_t; /* pager bitmask */ 41 42 struct swblock { 43 sw_bm_t swb_mask; /* bitmask of valid pages in this block */ 44 daddr_t swb_block; /* starting disk block for this block */ 45 }; 46 typedef struct swblock *sw_blk_t; 47 48 /* 49 * Swap pager private data. 50 */ 51 struct swpager { 52 vm_size_t sw_osize; /* size of object we are backing (bytes) */ 53 int sw_bsize; /* size of swap blocks (DEV_BSIZE units) */ 54 int sw_nblocks;/* number of blocks in list (sw_blk_t units) */ 55 sw_blk_t sw_blocks; /* pointer to list of swap blocks */ 56 short sw_flags; /* flags */ 57 short sw_poip; /* pageouts in progress */ 58 }; 59 typedef struct swpager *sw_pager_t; 60 61 #define SW_WANTED 0x01 62 #define SW_NAMED 0x02 63 64 #endif /* _SWAP_PAGER_ */ 65