The Cache and Backing Store Group contain the API for configuring caches and backing stores. More...
Classes | |
| struct | mdbm_bsops |
Macros | |
| #define | MDBM_CACHEMODE_NONE 0 |
| No caching behavior. More... | |
| #define | MDBM_CACHEMODE_LFU 1 |
| Entry with smallest number of accesses is evicted. More... | |
| #define | MDBM_CACHEMODE_LRU 2 |
| Entry with oldest access time is evicted. More... | |
| #define | MDBM_CACHEMODE_GDSF 3 |
| Greedy dual-size frequency (size and frequency) eviction. More... | |
| #define | MDBM_CACHEMODE_MAX 3 |
| Maximum cache mode value. More... | |
| #define | MDBM_CACHEMODE_EVICT_CLEAN_FIRST 0x10 |
| add to cachemode to evict clean items 1st More... | |
| #define | MDBM_CACHEMODE(m) ((m)&3) |
| Extracts cache mode. More... | |
| #define | MDBM_CACHEMODE_BITS (3 | MDBM_CACHEMODE_EVICT_CLEAN_FIRST) |
| Defines a mask for the cache mode, including control (eviction) bit. More... | |
| #define | MDBM_BSOPS_FILE ((const mdbm_bsops_t*)-1) |
| Backing store File identifier. More... | |
| #define | MDBM_BSOPS_MDBM ((const mdbm_bsops_t*)-2) |
| Backing store MDBM identifier. More... | |
Typedefs | |
| typedef struct mdbm_bsops | mdbm_bsops_t |
Functions | |
| int | mdbm_set_cachemode (MDBM *db, int cachemode) |
| Manage the database as a cache. More... | |
| int | mdbm_get_cachemode (MDBM *db) |
| Returns the current cache style of the database. More... | |
| const char * | mdbm_get_cachemode_name (int cachemode) |
| Returns the cache mode as a string. More... | |
| int | mdbm_set_backingstore (MDBM *cachedb, const mdbm_bsops_t *bsops, void *opt, int flags) |
| The backing-store support controls the in-memory cache as a read-through, write-through cache. More... | |
The Cache and Backing Store Group contain the API for configuring caches and backing stores.
| #define MDBM_CACHEMODE_NONE 0 |
No caching behavior.
| #define MDBM_CACHEMODE_LFU 1 |
Entry with smallest number of accesses is evicted.
| #define MDBM_CACHEMODE_LRU 2 |
Entry with oldest access time is evicted.
| #define MDBM_CACHEMODE_GDSF 3 |
Greedy dual-size frequency (size and frequency) eviction.
| #define MDBM_CACHEMODE_MAX 3 |
Maximum cache mode value.
| #define MDBM_CACHEMODE_EVICT_CLEAN_FIRST 0x10 |
add to cachemode to evict clean items 1st
| #define MDBM_CACHEMODE | ( | m | ) | ((m)&3) |
Extracts cache mode.
| #define MDBM_CACHEMODE_BITS (3 | MDBM_CACHEMODE_EVICT_CLEAN_FIRST) |
Defines a mask for the cache mode, including control (eviction) bit.
| #define MDBM_BSOPS_FILE ((const mdbm_bsops_t*)-1) |
Backing store File identifier.
| #define MDBM_BSOPS_MDBM ((const mdbm_bsops_t*)-2) |
Backing store MDBM identifier.
| typedef struct mdbm_bsops mdbm_bsops_t |
| int mdbm_set_cachemode | ( | MDBM * | db, |
| int | cachemode | ||
| ) |
Manage the database as a cache.
mdbm_set_cachemode must be called before data is inserted. Tracking metadata is stored with each entry which allows MDBM to do cache eviction via LRU, LFU, and GDSF (greedy-dual-size-frequency). MDBM also supports clean/dirty tracking and the application can supply a callback (see mdbm_set_backingstore) which is called by MDBM when a dirty entry is about to be evicted allowing the application to sync the entry to a backing store or perform some other type of "clean" operation.
NOTE: V3 API
| [in,out] | db | Database handle |
| [in] | cachemode | caching mode value (below) |
| -1 | Error, with errno set.
|
| 0 | Success |
Values for cachemode:
| int mdbm_get_cachemode | ( | MDBM * | db | ) |
Returns the current cache style of the database.
See the cachemode parameter in mdbm_set_cachemode for the valid values.
NOTE: V3 API
| [in,out] | db | Database handle |
| -1 | error, with errno set.
|
| MDBM_CACHEMODE_NONE | |
| MDBM_CACHEMODE_LFU | |
| MDBM_CACHEMODE_LRU | |
| MDBM_CACHEMODE_GDSF |
| const char* mdbm_get_cachemode_name | ( | int | cachemode | ) |
Returns the cache mode as a string.
NOTE: V3 API
| [in,out] | cachemode | Cache mode type (below) |
Values for cachemode:
| int mdbm_set_backingstore | ( | MDBM * | cachedb, |
| const mdbm_bsops_t * | bsops, | ||
| void * | opt, | ||
| int | flags | ||
| ) |
The backing-store support controls the in-memory cache as a read-through, write-through cache.
The backing-store interface uses a plugin model where each plugin supplies lock, unlock, fetch, store, and delete functions. Two predefined plugins are available: file-based(MDBM_BSOPS_FILE) and MDBM-based (MDBM_BSOPS_MDBM). Typically, a window will be set to access the backing store via mdbm_set_window_size since the backing store may be very large. Please refer to mdbm_set_window_size for window size restrictions.
An mdbm_store on cachedb must be used to update data in the backing store. An in-place update (fetching the data address using mdbm_fetch and directly modifying the data within the mapped db) will not get written through to the backing store.
Once backing store is set on the opened cache, it cannot be removed from the open cache.
If you use MDBM_BSOPS_MDBM to set an MDBM backing store, the cachedb will own the MDBM handle of the backing store, and cachedb will close it when the cache MDBM handle is closed. You should not make any MDBM calls directly using the backing store MDBM handle after passing it to mdbm_set_backingstore.
NOTE: V3 API
| [in,out] | cachedb | Database handle (for the cache database) |
| [in] | bsops | Can be MDBM_BSOPS_FILE, MDBM_BSOPS_MDBM, or user-supplied functions |
| [in] | opt | Depends on the bsops parameter. (ex., for MDBM_BSOPS_FILE opt should be a file path, or for MDBM_BSOPS_MDBM opt should be an MDBM database handle (opened with MDBM_OPEN_WINDOWED flag)) |
| [in] | flags | Depends on the bsops. Specify 0 if bsops is MDBM_BSOPS_MDBM. Specify O_DIRECT to prevent paging out important data when the bsops is MDBM_BSOPS_FILE. |
| -1 | Error |
| 0 | Success |