/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996-2001
 *	Sleepycat Software.  All rights reserved.
 *
 * $Id: mp.h,v 11.28 2002/01/06 21:44:28 bostic Exp $
 */

#ifndef	_DB_MP_H_
#define	_DB_MP_H_

struct __bh;		typedef struct __bh BH;
struct __db_mpreg;	typedef struct __db_mpreg DB_MPREG;
struct __mpool;		typedef struct __mpool MPOOL;

/* We require at least 20K of cache. */
#define	DB_CACHESIZE_MIN	(20 * 1024)

/*
 * DB_MPOOL --
 *	Per-process memory pool structure.
 */
struct __db_mpool {
	/* These fields need to be protected for multi-threaded support. */
	DB_MUTEX   *mutexp;		/* Structure thread lock. */

					/* List of pgin/pgout routines. */
	LIST_HEAD(__db_mpregh, __db_mpreg) dbregq;

					/* List of DB_MPOOLFILE's. */
	TAILQ_HEAD(__db_mpoolfileh, __db_mpoolfile) dbmfq;

	/* These fields are not thread-protected. */
	DB_ENV     *dbenv;		/* Reference to error information. */

	u_int32_t   nreg;		/* N underlying cache regions. */
	REGINFO	   *reginfo;		/* Underlying cache regions. */
	int	    extents;		/* Extent files opened by bhwrite. */
					/* Once set it's never cleared. */
};

/*
 * DB_MPREG --
 *	DB_MPOOL registry of pgin/pgout functions.
 */
struct __db_mpreg {
	LIST_ENTRY(__db_mpreg) q;	/* Linked list. */

	int ftype;			/* File type. */
					/* Pgin, pgout routines. */
	int (*pgin) __P((DB_ENV *, db_pgno_t, void *, DBT *));
	int (*pgout) __P((DB_ENV *, db_pgno_t, void *, DBT *));
};

/*
 * NCACHE --
 *	Select a cache based on the page number.  This assumes accesses are
 *	uniform across pages, which is probably OK -- what we really want to
 *	avoid is anything that puts all the pages for any single file in the
 *	same cache, as we expect that file access will be bursty.
 */
#define	NCACHE(mp, pgno)						\
	((pgno) % ((MPOOL *)mp)->nreg)

/*
 * NBUCKET --
 *	 We make the assumption that early pages of the file are more likely
 *	 to be retrieved than the later pages, which means the top bits will
 *	 be more interesting for hashing as they're less likely to collide.
 *	 That said, as 512 8K pages represents a 4MB file, so only reasonably
 *	 large files will have page numbers with any other than the bottom 9
 *	 bits set.  We XOR in the MPOOL offset of the MPOOLFILE that backs the
 *	 page, since that should also be unique for the page.  We don't want
 *	 to do anything very fancy -- speed is more important to us than using
 *	 good hashing.
 */
#define	NBUCKET(mc, mf_offset, pgno)					\
	(((pgno) ^ ((mf_offset) << 9)) % (mc)->htab_buckets)

/*
 * MPOOL --
 *	Shared memory pool region.
 */
struct __mpool {
	/*
	 * The memory pool can be broken up into individual pieces/files.
	 * Not what we would have liked, but on Solaris you can allocate
	 * only a little more than 2GB of memory in a contiguous chunk,
	 * and I expect to see more systems with similar issues.
	 *
	 * The first of these pieces/files describes the entire pool, all
	 * subsequent ones only describe a part of the cache.
	 */

	/*
	 * We single-thread memp_sync and memp_fsync calls.
	 *
	 * This mutex is intended *only* to single-thread access to the call,
	 */
	DB_MUTEX  sync_mutex;		/* Checkpoint lock. */

	/*
	 * The lsn and lsn_cnt fields, and the list of underlying MPOOLFILEs
	 * are thread-protected, by the region lock.
	 */
	DB_LSN	  lsn;			/* Maximum checkpoint LSN. */
	u_int32_t lsn_cnt;		/* Checkpoint buffers left to write. */

	SH_TAILQ_HEAD(__mpfq) mpfq;	/* List of MPOOLFILEs. */

	/*
	 * The nreg, regids and maint_off fields are not thread protected,
	 * as they are initialized during mpool creation, and not modified
	 * again.
	 */
	u_int32_t nreg;			/* Number of underlying REGIONS. */
	roff_t	  regids;		/* Array of underlying REGION Ids. */

#ifdef MUTEX_SYSTEM_RESOURCES
	roff_t	    maint_off;		/* Maintenance information offset */
#endif

	/* The flags field is thread-protected, by the region lock. */
#define	MP_LSN_RETRY	0x01		/* Retry all BH_WRITE buffers. */
	u_int32_t  flags;

	/*
	 * The following structure fields only describe the cache portion of
	 * the region.  The bhq and stat files are thread-protected, by the
	 * region lock.  The htab fields are not thread-protected, as they are
	 * initialized during mpool creation, and not modified again.
	 */
	SH_TAILQ_HEAD(__bhq) bhq;	/* LRU list of buffer headers. */

	int	    htab_buckets;	/* Number of hash table entries. */
	roff_t	    htab;		/* Hash table offset. */

	DB_MPOOL_STAT stat;		/* Per-cache mpool statistics. */
};

/*
 * MPOOLFILE --
 *	Shared DB_MPOOLFILE information.
 */
struct __mpoolfile {
	SH_TAILQ_ENTRY  q;		/* List of MPOOLFILEs */

	u_int32_t mpf_cnt;		/* Ref count: DB_MPOOLFILEs. */
	u_int32_t block_cnt;		/* Ref count: blocks in cache. */
	u_int32_t lsn_cnt;		/* Checkpoint buffers left to write. */

	int	  ftype;		/* File type. */
	int32_t	  lsn_off;		/* Page's LSN offset. */
	u_int32_t clear_len;		/* Bytes to clear on page create. */

	roff_t	  path_off;		/* File name location. */
	roff_t	  fileid_off;		/* File identification location. */

	roff_t	  pgcookie_len;		/* Pgin/pgout cookie length. */
	roff_t	  pgcookie_off;		/* Pgin/pgout cookie location. */

	db_pgno_t last_pgno;		/* Last page in the file. */
	db_pgno_t orig_last_pgno;	/* Original last page in the file. */

	DB_MPOOL_FSTAT stat;		/* Per-file mpool statistics. */

#define	MP_CAN_MMAP	0x01		/* If the file can be mmap'd. */
#define	MP_DEADFILE	0x02		/* Dirty pages can simply be trashed. */
#define	MP_EXTENT	0x04		/* Extent file. */
#define	MP_TEMP		0x08		/* Backing file is a temporary. */
#define	MP_UNLINK	0x10		/* Unlink file on last close. */
	u_int32_t  flags;
};

/*
 * BH_TO_CACHE --
 *	Return the cache where we can find the specified buffer header.
 */
#define	BH_TO_CACHE(dbmp, bhp)						\
	(dbmp)->reginfo[NCACHE((dbmp)->reginfo[0].primary, (bhp)->pgno)].primary

/*
 * BH --
 *	Buffer header.
 */
struct __bh {
	DB_MUTEX	mutex;		/* Buffer thread/process lock. */

	u_int16_t	ref;		/* Reference count. */

#define	BH_CALLPGIN	0x001		/* Page needs to be reworked... */
#define	BH_DIRTY	0x002		/* Page was modified. */
#define	BH_DIRTY_CREATE	0x004		/* Page created, must be written. */
#define	BH_DISCARD	0x008		/* Page is useless. */
#define	BH_LOCKED	0x010		/* Page is locked (I/O in progress). */
#define	BH_SYNC		0x020		/* memp sync: write the page */
#define	BH_SYNC_LOGFLSH	0x040		/* memp sync: also flush the log */
#define	BH_TRASH	0x080		/* Page is garbage. */
	u_int16_t  flags;

	SH_TAILQ_ENTRY	q;		/* LRU queue. */
	SH_TAILQ_ENTRY	hq;		/* MPOOL hash bucket queue. */

	db_pgno_t pgno;			/* Underlying MPOOLFILE page number. */
	roff_t	  mf_offset;		/* Associated MPOOLFILE offset. */

	/*
	 * !!!
	 * This array must be at least size_t aligned -- the DB access methods
	 * put PAGE and other structures into it, and then access them directly.
	 * (We guarantee size_t alignment to applications in the documentation,
	 * too.)
	 */
	u_int8_t   buf[1];		/* Variable length data. */
};

#include "mp_ext.h"
#endif /* !_DB_MP_H_ */
