/*- * See the file LICENSE for redistribution information. * * Copyright (c) 1996-2003 * Sleepycat Software. All rights reserved. * * $Id: mp.h,v 1.2 2004/03/30 01:21:28 jtownsen 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) /* * DB_MPOOLFILE initialization methods cannot be called after open is called, * other methods cannot be called before open is called */ #define MPF_ILLEGAL_AFTER_OPEN(dbmfp, name) \ if (F_ISSET(dbmfp, MP_OPEN_CALLED)) \ return (__db_mi_open((dbmfp)->dbenv, name, 1)); #define MPF_ILLEGAL_BEFORE_OPEN(dbmfp, name) \ if (!F_ISSET(dbmfp, MP_OPEN_CALLED)) \ return (__db_mi_open((dbmfp)->dbenv, name, 0)); 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. */ /* * We track page puts so that we can decide when allocation is never * going to succeed. We don't lock the field, all we care about is * if it changes. */ u_int32_t put_counter; /* Count of page put calls. */ }; 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 -- * 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. */ /* * We normally don't lock the deadfile field when we read it since we * only care if the field is zero or non-zero. We do lock on read when * searching for a matching MPOOLFILE -- see that code for more detail. */ int32_t deadfile; /* Dirty pages can be discarded. */ /* 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. */ db_pgno_t maxpgno; /* Maximum page number. */ /* * 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. */ int32_t ftype; /* File type. */ /* * 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. */ int32_t priority; /* Priority when unpinning buffer. */ /* * There are potential races with the file_written field (many threads * may be writing blocks at the same time), and with no_backing_file * and unlink_on_close fields, as they may be set while other threads * are reading them. However, we only care if the value of these fields * are zero or non-zero, so don't lock the memory. * * !!! * Theoretically, a 64-bit architecture could put two of these fields * in a single memory operation and we could race. I have never seen * an architecture where that's a problem, and I believe Java requires * that to never be the case. */ int32_t file_written; /* File was written. */ int32_t no_backing_file; /* Never open a backing file. */ int32_t unlink_on_close; /* Unlink file on last close. */ /* * 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. */ DB_MPOOL_FSTAT stat; /* Per-file mpool statistics. */ /* * The remaining fields are initialized at open and never subsequently * modified. */ 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. */ /* * The flags are initialized at open and never subsequently modified. */ #define MP_CAN_MMAP 0x001 /* If the file can be mmap'd. */ #define MP_DIRECT 0x002 /* No OS buffering. */ #define MP_EXTENT 0x004 /* Extent file. */ #define MP_FAKE_DEADFILE 0x008 /* Deadfile field: fake flag. */ #define MP_FAKE_FILEWRITTEN 0x010 /* File_written field: fake flag. */ #define MP_FAKE_NB 0x020 /* No_backing_file field: fake flag. */ #define MP_FAKE_UOC 0x040 /* Unlink_on_close field: fake flag. */ #define MP_NOT_DURABLE 0x080 /* File is not durable. */ #define MP_TEMP 0x100 /* Backing file is a temporary. */ 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_ */