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619edcce KM |
1 | /* |
2 | * Copyright (c) 1990 University of Utah. | |
3 | * Copyright (c) 1991 The Regents of the University of California. | |
4 | * 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 | * | |
202cd3ae | 12 | * @(#)swap_pager.h 7.2 (Berkeley) %G% |
619edcce KM |
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 | ||
619edcce | 64 | #endif /* _SWAP_PAGER_ */ |