Yi Wu 72f8cc703c LRU cache mid-point insertion ... Summary: Add mid-point insertion functionality to LRU cache. Caller of `Cache::Insert()` can set an additional parameter to make a cache entry have higher priority. The LRU cache will reserve at most `capacity * high_pri_pool_pct` bytes for high-pri cache entries. If `high_pri_pool_pct` is zero, the cache degenerates to normal LRU cache. Context: If we are to put index and filter blocks into RocksDB block cache, index/filter block can be swap out too early. We want to add an option to RocksDB to reserve some capacity in block cache just for index/filter blocks, to mitigate the issue. In later diffs I'll update block based table reader to use the interface to cache index/filter blocks at high priority, and expose the option to `DBOptions` and make it dynamic changeable. Test Plan: unit test. Reviewers: IslamAbdelRahman, sdong, lightmark Reviewed By: lightmark Subscribers: andrewkr, dhruba, march, leveldb Differential Revision: https://reviews.facebook.net/D61977		2016-08-19 16:43:31 -07:00
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rocksdb	LRU cache mid-point insertion	2016-08-19 16:43:31 -07:00