f89caa127b
Summary: This patch adds direct IO capability to RocksDB Env. The direct IO capability is required for persistent cache since NVM is best accessed as 4K direct IO. SSDs can leverage direct IO for reading. Direct IO requires the offset and size be sector size aligned, and memory to be kernel page aligned. Since neither RocksDB/Persistent read cache data layout is aligned to sector size, the code can accommodate reading unaligned IO size (or unaligned memory) at the cost of an alloc/copy. The write code path expects the size and memory to be aligned. Test Plan: Run RocksDB unit tests Reviewers: sdong Subscribers: andrewkr, dhruba, leveldb Differential Revision: https://reviews.facebook.net/D57393
RocksDB: A Persistent Key-Value Store for Flash and RAM Storage
RocksDB is developed and maintained by Facebook Database Engineering Team. It is built on earlier work on LevelDB by Sanjay Ghemawat (sanjay@google.com) and Jeff Dean (jeff@google.com)
This code is a library that forms the core building block for a fast key value server, especially suited for storing data on flash drives. It has a Log-Structured-Merge-Database (LSM) design with flexible tradeoffs between Write-Amplification-Factor (WAF), Read-Amplification-Factor (RAF) and Space-Amplification-Factor (SAF). It has multi-threaded compactions, making it specially suitable for storing multiple terabytes of data in a single database.
Start with example usage here: https://github.com/facebook/rocksdb/tree/master/examples
See the github wiki for more explanation.
The public interface is in include/. Callers should not include or
rely on the details of any other header files in this package. Those
internal APIs may be changed without warning.
Design discussions are conducted in https://www.facebook.com/groups/rocksdb.dev/