Xinye Tao

Support Direct I/O

5

Simple [benchmark](https://gist.github.com/tabokie/a290ec746a2fb887f55e0894362dcc84) shows more than 20% throughput improvement from direct I/O. This task is preferred to be stacked over #165.

read-on-write problem refers to when an unaligned write I/O is issued, an additional read is needed to prefetch the data into page cache. In practice we have only observed this...

Write to multiple WALs concurrently to leverage hardware parallelism. ~Raft Engine provides a `WriteToken` that maps to a WAL stream underneath. If `WriteToken` is not provided, it will write to...

1. Expanding `FileSystem` interface to provide async tasking capability: ``` trait AsyncContext { fn wait() -> Result; } trait FileSystem { pub type AsyncIoContext: AsyncContext; fn new_async_context() -> AsyncContext; fn...

## Bug Report ### Description During `Append` queue rewrite, key value pairs of targeted Raft groups are scanned out and rewritten to `Rewrite` queue. After that, data files in `Append`...