mp.h
上传用户:romrleung
上传日期:2022-05-23
资源大小:18897k
文件大小:10k
- /*-
- * 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_ */