/*-
* See the file LICENSE for redistribution information.
*
* Copyright (c) 1996-2002
* Sleepycat Software. All rights reserved.
*
* $Id: mp.h,v 11.44 2002/08/06 06:11:21 bostic Exp $
*/
#ifndef _DB_MP_H_
#define _DB_MP_H_
struct __bh; typedef struct __bh BH;
struct __db_mpool_hash; typedef struct __db_mpool_hash DB_MPOOL_HASH;
struct __db_mpreg; typedef struct __db_mpreg DB_MPREG;
struct __mpool; typedef struct __mpool MPOOL;
/* We require at least 20KB of cache. */
#define DB_CACHESIZE_MIN (20 * 1024)
typedef enum {
DB_SYNC_ALLOC, /* Flush for allocation. */
DB_SYNC_CACHE, /* Checkpoint or flush entire cache. */
DB_SYNC_FILE, /* Flush file. */
DB_SYNC_TRICKLE /* Trickle sync. */
} db_sync_op;
/*
* 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;
/*
* The dbenv, nreg and reginfo fields are not thread protected,
* as they are initialized during mpool creation, and not modified
* again.
*/
DB_ENV *dbenv; /* Enclosing environment. */
u_int32_t nreg; /* N underlying cache regions. */
REGINFO *reginfo; /* Underlying cache regions. */
};
/*
* DB_MPREG --
* DB_MPOOL registry of pgin/pgout functions.
*/
struct __db_mpreg {
LIST_ENTRY(__db_mpreg) q; /* Linked list. */
int32_t 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 file and the page number. Assumes accesses
* are uniform across pages, which is probably OK. What we really want to
* avoid is anything that puts all pages from any single file in the same
* cache, as we expect that file access will be bursty, and to avoid
* putting all page number N pages in the same cache as we expect access
* to the metapages (page 0) and the root of a btree (page 1) to be much
* more frequent than a random data page.
*/
#define NCACHE(mp, mf_offset, pgno) \
(((pgno) ^ ((mf_offset) >> 3)) % ((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.
*
* While this structure is duplicated in each piece of the cache,
* the first of these pieces/files describes the entire pool, the
* second only describe a piece of the cache.
*/
/*
* The lsn field and list of underlying MPOOLFILEs are thread protected
* by the region lock.
*/
DB_LSN lsn; /* Maximum checkpoint LSN. */
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 HAVE_MUTEX_SYSTEM_RESOURCES
roff_t maint_off; /* Maintenance information offset */
#endif
/*
* The following structure fields only describe the per-cache portion
* of the region.
*
* The htab and htab_buckets fields are not thread protected as they
* are initialized during mpool creation, and not modified again.
*
* The last_checked and lru_count fields are thread protected by
* the region lock.
*/
int htab_buckets; /* Number of hash table entries. */
roff_t htab; /* Hash table offset. */
u_int32_t last_checked; /* Last bucket checked for free. */
u_int32_t lru_count; /* Counter for buffer LRU */
/*
* The stat fields are generally not thread protected, and cannot be
* trusted. Note that st_pages is an exception, and is always updated
* inside a region lock (although it is sometimes read outside of the
* region lock).
*/
DB_MPOOL_STAT stat; /* Per-cache mpool statistics. */
};
struct __db_mpool_hash {
DB_MUTEX hash_mutex; /* Per-bucket mutex. */
DB_HASHTAB hash_bucket; /* Head of bucket. */
u_int32_t hash_page_dirty;/* Count of dirty pages. */
u_int32_t hash_priority; /* Minimum priority of bucket buffer. */
};
/*
* The base mpool priority is 1/4th of the name space, or just under 2^30.
* When the LRU counter wraps, we shift everybody down to a base-relative
* value.
*/
#define MPOOL_BASE_DECREMENT (UINT32_T_MAX - (UINT32_T_MAX / 4))
/*
* Mpool priorities from low to high. Defined in terms of fractions of the
* buffers in the pool.
*/
#define MPOOL_PRI_VERY_LOW -1 /* Dead duck. Check and set to 0. */
#define MPOOL_PRI_LOW -2 /* Low. */
#define MPOOL_PRI_DEFAULT 0 /* No adjustment -- special case.*/
#define MPOOL_PRI_HIGH 10 /* With the dirty buffers. */
#define MPOOL_PRI_DIRTY 10 /* Dirty gets a 10% boost. */
#define MPOOL_PRI_VERY_HIGH 1 /* Add number of buffers in pool. */
/*
* MPOOLFILE_IGNORE --
* Discard an MPOOLFILE and any buffers it references: update the flags
* so we never try to write buffers associated with the file, nor can we
* find it when looking for files to join. In addition, clear the ftype
* field, there's no reason to post-process pages, they can be discarded
* by any thread.
*
* Expects the MPOOLFILE mutex to be held.
*/
#define MPOOLFILE_IGNORE(mfp) { \
(mfp)->ftype = 0; \
F_SET(mfp, MP_DEADFILE); \
}
/*
* MPOOLFILE --
* Shared DB_MPOOLFILE information.
*/
struct __mpoolfile {
DB_MUTEX mutex;
/* Protected by MPOOLFILE mutex. */
u_int32_t mpf_cnt; /* Ref count: DB_MPOOLFILEs. */
u_int32_t block_cnt; /* Ref count: blocks in cache. */
roff_t path_off; /* File name location. */
/* Protected by mpool cache 0 region lock. */
SH_TAILQ_ENTRY q; /* List of MPOOLFILEs */
db_pgno_t last_pgno; /* Last page in the file. */
db_pgno_t orig_last_pgno; /* Original last page in the file. */
/*
* None of the following fields are thread protected.
*
* There are potential races with the ftype field because it's read
* without holding a lock. However, it has to be set before adding
* any buffers to the cache that depend on it being set, so there
* would need to be incorrect operation ordering to have a problem.
*
* There are potential races with the priority field because it's read
* without holding a lock. However, a collision is unlikely and if it
* happens is of little consequence.
*
* We do not protect the statistics in "stat" because of the cost of
* the mutex in the get/put routines. There is a chance that a count
* will get lost.
*
* The remaining fields are initialized at open and never subsequently
* modified, except for the MP_DEADFILE, which is only set and never
* unset. (If there was more than one flag that was subsequently set,
* there might be a race, but with a single flag there can't be.)
*/
int32_t ftype; /* File type. */
int32_t priority; /* Priority when unpinning buffer. */
DB_MPOOL_FSTAT stat; /* Per-file mpool statistics. */
int32_t lsn_off; /* Page's LSN offset. */
u_int32_t clear_len; /* Bytes to clear on page create. */
roff_t fileid_off; /* File ID string location. */
roff_t pgcookie_len; /* Pgin/pgout cookie length. */
roff_t pgcookie_off; /* Pgin/pgout cookie location. */
#define MP_CAN_MMAP 0x01 /* If the file can be mmap'd. */
#define MP_DEADFILE 0x02 /* Dirty pages can simply be trashed. */
#define MP_DIRECT 0x04 /* No OS buffering. */
#define MP_EXTENT 0x08 /* Extent file. */
#define MP_TEMP 0x10 /* Backing file is a temporary. */
#define MP_UNLINK 0x20 /* Unlink file on last close. */
u_int32_t flags;
};
/*
* BH --
* Buffer header.
*/
struct __bh {
DB_MUTEX mutex; /* Buffer thread/process lock. */
u_int16_t ref; /* Reference count. */
u_int16_t ref_sync; /* Sync wait-for reference count. */
#define BH_CALLPGIN 0x001 /* Convert the page before use. */
#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_TRASH 0x020 /* Page is garbage. */
u_int16_t flags;
u_int32_t priority; /* LRU priority. */
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 "dbinc_auto/mp_ext.h"
#endif /* !_DB_MP_H_ */
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