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mdbx: add mdbx_is_readahead_reasonable().

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Change-Id: Iac090a9050d6b046b62b2c79cefbc70cc62c9144
This commit is contained in:
Leonid Yuriev
2019-10-12 14:16:45 +03:00
parent 3ce4c3a0e4
commit bb922c208c
3 changed files with 140 additions and 0 deletions
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18
mdbx.h
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@@ -965,6 +965,10 @@ LIBMDBX_API char *mdbx_dump_val(const MDBX_val *key, char *const buf,
* may help random read performance when the DB is larger than RAM and system
* RAM is full.
*
* NOTE: The mdbx_is_readahead_reasonable() function allows to quickly find out
* whether to use readahead or not based on the size of the data and the
* amount of available memory.
*
* This flag affects only at environment opening and can't be changed after. */
#define MDBX_NORDAHEAD 0x800000u
@@ -2014,6 +2018,20 @@ LIBMDBX_API int mdbx_env_set_geometry(MDBX_env *env, intptr_t size_lower,
intptr_t pagesize);
LIBMDBX_API int mdbx_env_set_mapsize(MDBX_env *env, size_t size);
/* Find out whether to use readahead or not, based on the given database size
* and the amount of available memory.
*
* [in] volume The expected database size in bytes.
* [in] redundancy Additional reserve or overload in case of negative value.
*
* Returns:
* - MDBX_RESULT_TRUE = readahead is reasonable.
* - MDBX_RESULT_FALSE = readahead is NOT reasonable, i.e. MDBX_NORDAHEAD
* is useful to open environment by mdbx_env_open().
* - Otherwise the error code. */
LIBMDBX_API int mdbx_is_readahead_reasonable(size_t volume,
intptr_t redundancy);
/* The minimal database page size in bytes. */
#define MDBX_MIN_PAGESIZE 512
__inline intptr_t mdbx_limits_pgsize_min(void) { return MDBX_MIN_PAGESIZE; }