BSD 4_4 release

[unix-history] / usr / src / sys / vm / swap_pager.h

/*
* Copyright (c) 1990 University of Utah.
* Copyright (c) 1991, 1993
*      The Regents of the University of California.  All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* the Systems Programming Group of the University of Utah Computer
* Science Department.
*
* 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 the University of
*      California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
*    may be used to endorse or promote products derived from this software
*    without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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.
*
*      @(#)swap_pager.h        8.1 (Berkeley) 6/11/93
*/

#ifndef _SWAP_PAGER_
#define _SWAP_PAGER_    1

/*
* In the swap pager, the backing store for an object is organized as an
* array of some number of "swap blocks".  A swap block consists of a bitmask
* and some number of contiguous DEV_BSIZE disk blocks.  The minimum size
* of a swap block is:
*
*      max(PAGE_SIZE, dmmin*DEV_BSIZE)                 [ 32k currently ]
*
* bytes (since the pager interface is page oriented), the maximum size is:
*
*      min(#bits(swb_mask)*PAGE_SIZE, dmmax*DEV_BSIZE) [ 128k currently ]
*
* where dmmin and dmmax are left over from the old VM interface.  The bitmask
* (swb_mask) is used by swap_pager_haspage() to determine if a particular
* page has actually been written; i.e. the pager copy of the page is valid.
* All swap blocks in the backing store of an object will be the same size.
*
* The reason for variable sized swap blocks is to reduce fragmentation of
* swap resources.  Whenever possible we allocate smaller swap blocks to
* smaller objects.  The swap block size is determined from a table of
* object-size vs. swap-block-size computed at boot time.
*/
typedef int     sw_bm_t;        /* pager bitmask */

struct  swblock {
       sw_bm_t  swb_mask;      /* bitmask of valid pages in this block */
       daddr_t  swb_block;     /* starting disk block for this block */
};
typedef struct swblock  *sw_blk_t;

/*
* Swap pager private data.
*/
struct swpager {
       vm_size_t    sw_osize;  /* size of object we are backing (bytes) */
       int          sw_bsize;  /* size of swap blocks (DEV_BSIZE units) */
       int          sw_nblocks;/* number of blocks in list (sw_blk_t units) */
       sw_blk_t     sw_blocks; /* pointer to list of swap blocks */
       short        sw_flags;  /* flags */
       short        sw_poip;   /* pageouts in progress */
};
typedef struct swpager  *sw_pager_t;

#define SW_WANTED       0x01
#define SW_NAMED        0x02

#endif  /* _SWAP_PAGER_ */