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Annotation of Net2/vm/swap_pager.h, revision 1.1

1.1     ! root        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:  * 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        7.1 (Berkeley) 12/5/90
        !            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:  */
        !            66: typedef        int     sw_bm_t;        /* pager bitmask */
        !            67: 
        !            68: struct 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: };
        !            72: typedef struct swblock *sw_blk_t;
        !            73: 
        !            74: /*
        !            75:  * Swap pager private data.
        !            76:  */
        !            77: struct 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: };
        !            85: typedef struct swpager *sw_pager_t;
        !            86: 
        !            87: #define        SW_WANTED       0x01
        !            88: #define SW_NAMED       0x02
        !            89: 
        !            90: #ifdef KERNEL
        !            91: 
        !            92: void           swap_pager_init();
        !            93: vm_pager_t     swap_pager_alloc();
        !            94: void           swap_pager_dealloc();
        !            95: boolean_t      swap_pager_getpage(), swap_pager_putpage();
        !            96: boolean_t      swap_pager_haspage();
        !            97: 
        !            98: struct pagerops swappagerops = {
        !            99:        swap_pager_init,
        !           100:        swap_pager_alloc,
        !           101:        swap_pager_dealloc,
        !           102:        swap_pager_getpage,
        !           103:        swap_pager_putpage,
        !           104:        swap_pager_haspage
        !           105: };
        !           106: 
        !           107: int            swap_pager_iodone();
        !           108: boolean_t      swap_pager_clean();
        !           109: 
        !           110: #endif
        !           111: 
        !           112: #endif /* _SWAP_PAGER_ */

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