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/*-
* See the file LICENSE for redistribution information.
*
* Copyright (c) 1996, 1997
* Sleepycat Software. All rights reserved.
*
* @(#)mp.h 10.25 (Sleepycat) 1/8/98
*/
struct __bh; typedef struct __bh BH;
struct __db_mpreg; typedef struct __db_mpreg DB_MPREG;
struct __mpool; typedef struct __mpool MPOOL;
struct __mpoolfile; typedef struct __mpoolfile MPOOLFILE;
/* Default mpool name. */
#define DB_DEFAULT_MPOOL_FILE "__db_mpool.share"
/*
* We default to 128K (16 8K pages) if the user doesn't specify, and
* require a minimum of 20K.
*/
#define DB_CACHESIZE_DEF (128 * 1024)
#define DB_CACHESIZE_MIN ( 20 * 1024)
#define INVALID 0 /* Invalid shared memory offset. */
/*
* There are three ways we do locking in the mpool code:
*
* Locking a handle mutex to provide concurrency for DB_THREAD operations.
* Locking the region mutex to provide mutual exclusion while reading and
* writing structures in the shared region.
* Locking buffer header mutexes during I/O.
*
* The first will not be further described here. We use the shared mpool
* region lock to provide mutual exclusion while reading/modifying all of
* the data structures, including the buffer headers. We use a per-buffer
* header lock to wait on buffer I/O. The order of locking is as follows:
*
* Searching for a buffer:
* Acquire the region lock.
* Find the buffer header.
* Increment the reference count (guarantee the buffer stays).
* While the BH_LOCKED flag is set (I/O is going on) {
* Release the region lock.
* Explicitly yield the processor if it's not the first pass
* through this loop, otherwise, we can simply spin because
* we'll be simply switching between the two locks.
* Request the buffer lock.
* The I/O will complete...
* Acquire the buffer lock.
* Release the buffer lock.
* Acquire the region lock.
* }
* Return the buffer.
*
* Reading/writing a buffer:
* Acquire the region lock.
* Find/create the buffer header.
* If reading, increment the reference count (guarantee the buffer stays).
* Set the BH_LOCKED flag.
* Acquire the buffer lock (guaranteed not to block).
* Release the region lock.
* Do the I/O and/or initialize the buffer contents.
* Release the buffer lock.
* At this point, the buffer lock is available, but the logical
* operation (flagged by BH_LOCKED) is not yet completed. For
* this reason, among others, threads checking the BH_LOCKED flag
* must loop around their test.
* Acquire the region lock.
* Clear the BH_LOCKED flag.
* Release the region lock.
* Return/discard the buffer.
*
* Pointers to DB_MPOOL, MPOOL, DB_MPOOLFILE and MPOOLFILE structures are not
* reacquired when a region lock is reacquired because they couldn't have been
* closed/discarded and because they never move in memory.
*/
#define LOCKINIT(dbmp, mutexp) \
if (F_ISSET(dbmp, MP_LOCKHANDLE | MP_LOCKREGION)) \
(void)__db_mutex_init(mutexp, \
MUTEX_LOCK_OFFSET((dbmp)->maddr, mutexp))
#define LOCKHANDLE(dbmp, mutexp) \
if (F_ISSET(dbmp, MP_LOCKHANDLE)) \
(void)__db_mutex_lock(mutexp, (dbmp)->fd)
#define UNLOCKHANDLE(dbmp, mutexp) \
if (F_ISSET(dbmp, MP_LOCKHANDLE)) \
(void)__db_mutex_unlock(mutexp, (dbmp)->fd)
#define LOCKREGION(dbmp) \
if (F_ISSET(dbmp, MP_LOCKREGION)) \
(void)__db_mutex_lock(&((RLAYOUT *)(dbmp)->mp)->lock, \
(dbmp)->fd)
#define UNLOCKREGION(dbmp) \
if (F_ISSET(dbmp, MP_LOCKREGION)) \
(void)__db_mutex_unlock(&((RLAYOUT *)(dbmp)->mp)->lock, \
(dbmp)->fd)
#define LOCKBUFFER(dbmp, bhp) \
if (F_ISSET(dbmp, MP_LOCKREGION)) \
(void)__db_mutex_lock(&(bhp)->mutex, (dbmp)->fd)
#define UNLOCKBUFFER(dbmp, bhp) \
if (F_ISSET(dbmp, MP_LOCKREGION)) \
(void)__db_mutex_unlock(&(bhp)->mutex, (dbmp)->fd)
/*
* DB_MPOOL --
* Per-process memory pool structure.
*/
struct __db_mpool {
/* These fields need to be protected for multi-threaded support. */
db_mutex_t *mutexp; /* Structure 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 protected. */
DB_ENV *dbenv; /* Reference to error information. */
MPOOL *mp; /* Address of the shared MPOOL. */
void *maddr; /* Address of mmap'd region. */
void *addr; /* Address of shalloc() region. */
DB_HASHTAB *htab; /* Hash table of bucket headers. */
int fd; /* Underlying mmap'd fd. */
#define MP_ISPRIVATE 0x01 /* Private, so local memory. */
#define MP_LOCKHANDLE 0x02 /* Threaded, lock handles and region. */
#define MP_LOCKREGION 0x04 /* Concurrent access, lock region. */
#define MP_MALLOC 0x08 /* If region in allocated memory. */
u_int32_t flags;
};
/*
* 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_pgno_t, void *, DBT *));
int (*pgout) __P((db_pgno_t, void *, DBT *));
};
/*
* DB_MPOOLFILE --
* Per-process DB_MPOOLFILE information.
*/
struct __db_mpoolfile {
/* These fields need to be protected for multi-threaded support. */
db_mutex_t *mutexp; /* Structure lock. */
int fd; /* Underlying file descriptor. */
u_int32_t pinref; /* Pinned block reference count. */
/* These fields are not protected. */
TAILQ_ENTRY(__db_mpoolfile) q; /* Linked list of DB_MPOOLFILE's. */
DB_MPOOL *dbmp; /* Overlying DB_MPOOL. */
MPOOLFILE *mfp; /* Underlying MPOOLFILE. */
void *addr; /* Address of mmap'd region. */
size_t len; /* Length of mmap'd region. */
/* These fields need to be protected for multi-threaded support. */
#define MP_READONLY 0x01 /* File is readonly. */
#define MP_UPGRADE 0x02 /* File descriptor is readwrite. */
#define MP_UPGRADE_FAIL 0x04 /* Upgrade wasn't possible. */
u_int32_t flags;
};
/*
* MPOOL --
* Shared memory pool region. One of these is allocated in shared
* memory, and describes the pool.
*/
struct __mpool {
RLAYOUT rlayout; /* General region information. */
SH_TAILQ_HEAD(__bhq) bhq; /* LRU list of buckets. */
SH_TAILQ_HEAD(__bhfq) bhfq; /* Free buckets. */
SH_TAILQ_HEAD(__mpfq) mpfq; /* List of MPOOLFILEs. */
/*
* We make the assumption that the early pages of the file are far
* more likely to be retrieved than the later pages, which means
* that the top bits are more interesting for hashing since they're
* less likely to collide. On the other hand, since 512 4K pages
* represents a 2MB file, only the bottom 9 bits of the page number
* are likely to be set. We XOR in the offset in the MPOOL of the
* MPOOLFILE that backs this particular page, since that should also
* be unique for the page.
*/
#define BUCKET(mp, mf_offset, pgno) \
(((pgno) ^ ((mf_offset) << 9)) % (mp)->htab_buckets)
size_t htab; /* Hash table offset. */
size_t htab_buckets; /* Number of hash table entries. */
DB_LSN lsn; /* Maximum checkpoint LSN. */
int lsn_cnt; /* Checkpoint buffers left to write. */
DB_MPOOL_STAT stat; /* Global mpool statistics. */
#define MP_LSN_RETRY 0x01 /* Retry all BH_WRITE buffers. */
u_int32_t flags;
};
/*
* MPOOLFILE --
* Shared DB_MPOOLFILE information.
*/
struct __mpoolfile {
SH_TAILQ_ENTRY q; /* List of MPOOLFILEs */
u_int32_t ref; /* Reference count. */
int ftype; /* File type. */
int lsn_off; /* Page's LSN offset. */
size_t path_off; /* File name location. */
size_t fileid_off; /* File identification location. */
size_t pgcookie_len; /* Pgin/pgout cookie length. */
size_t pgcookie_off; /* Pgin/pgout cookie location. */
int lsn_cnt; /* Checkpoint buffers left to write. */
db_pgno_t last_pgno; /* Last page in the file. */
#define MP_CAN_MMAP 0x01 /* If the file can be mmap'd. */
#define MP_TEMP 0x02 /* Backing file is a temporary. */
u_int32_t flags;
DB_MPOOL_FSTAT stat; /* Per-file mpool statistics. */
};
/*
* BH --
* Buffer header.
*/
struct __bh {
db_mutex_t mutex; /* Structure 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_DISCARD 0x004 /* Page is useless. */
#define BH_LOCKED 0x008 /* Page is locked (I/O in progress). */
#define BH_TRASH 0x010 /* Page is garbage. */
#define BH_WRITE 0x020 /* Page scheduled for writing. */
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. */
size_t mf_offset; /* Associated MPOOLFILE offset. */
/*
* !!!
* This array must be size_t aligned -- the DB access methods put PAGE
* and other structures into it, and expect to be able to access them
* directly. (We guarantee size_t alignment in the db_mpool(3) manual
* page as well.)
*/
u_int8_t buf[1]; /* Variable length data. */
};
#include "mp_ext.h"
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