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Diffstat (limited to 'bdb/dbinc/mp.h')
| -rw-r--r-- | bdb/dbinc/mp.h | 293 |
1 files changed, 293 insertions, 0 deletions
diff --git a/bdb/dbinc/mp.h b/bdb/dbinc/mp.h new file mode 100644 index 00000000000..5c805b92364 --- /dev/null +++ b/bdb/dbinc/mp.h @@ -0,0 +1,293 @@ +/*- + * 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_ */ |