Feature request: Parallel file reading

[nh2]

Currently mksquashfs seems to use a single reader thread.

Many current devices only achieve optimal throughput when files are read from them in parallel:

• current SSDs (which require a high queue depth)
• large RAID arrays (e.g. servers with 16 disks in)
• network file systems (parallelism hiding network latency)

Could mksquashfs add (configurable) threaded reading?

Thanks!