84be8984da
doxfilter modified to know about new macros: @m_page, @m_if, @m_else, @m_endif. Pages with @m_page have all its snippets/subpages point to the language specific example/subpage. The java examples directory added to EXAMPLE_PATH in Doxyfile. Added @m_page to any doc page that also needs a Java version. Added cast to wiredtiger.i for stricter compiler checking.
42 lines
2.2 KiB
Plaintext
42 lines
2.2 KiB
Plaintext
/*! @m_page{{c,java},shared_cache,Per-process shared caches}
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WiredTiger supports sharing a single cache among multiple databases within
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a process.
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An application configures a shared cache by specifying a shared_cache name
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to the ::wiredtiger_open function. Applications can optionally
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set a minimum amount of cache any connection in the pool will be assigned
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and the granularity at which the cache pool is redistributed among
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connections - called the chunk size.
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The shared cache implementation assigns a certain amount of cache to each
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participating database. Each database manages its allocated cache
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as it would when not using a shared cache - thus databases using a shared
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cache can have different eviction policies. There is a thread that monitors
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the cache usage of each database and redistributes the cache among
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participants according to where it is most likely to improve performance.
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The cache is redistributed in chunks which are of a configurable size. Once
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a database has had a chunk of cache added or removed it will be given
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time to start effectively using that cache before it is considered for further
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adjustment. If a small chunk size is configured it will take longer for the
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shared cache to adjust to changes in participants. Reallocation of resources
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happens periodically and whenever a database joins the shared cache.
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The reallocation of resources is determined by comparing the amount of eviction
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activity in a particular database to that of the other participating databases.
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When a database is opened it will be allocated the amount of cache configured
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as the shared cache minimum, regardless of whether the cache pool is currently
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fully utilized. Other databases will have their assigned cache size
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reduced so the total cache size used will return within the bounds - there
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may be a period when the actual usage exceeds the configured maximum.
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This is especially likely if many databases join the shared cache in a short
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period. When a database is closed any resources it is using are distributed
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among the other databases.
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WiredTiger shared cache tuning options can be configured when first opening a
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database via ::wiredtiger_open or changed after open using the
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WT_CONNECTION::reconfigure method.
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*/
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