I'm wondering that why leveldb use mmap based writing at first， then replace it with stdio based writing.
According to 1.15 Release Note
. ' Has a minor impact (0.5 microseconds) on microbenchmarks for asynchronous writes. Synchronous writes speed up from 30ms to 10ms on linux/ext4.'
1). I think asynchronous or synchronous writes means wether to use fsync for the write operation, is it that？
2). If so, I prefer the mmap version, because asynchronous writes is much more common for my situation, what's your opion?
Also, I'm new to leveldb benchmark, how can I benchmark this?