how many threads to run in java?

Question

I had this brilliant idea to speed up the time needed for generating 36 files: use 36 threads!! Unfortunately if I start one connection (one j2ssh connection object

Answer 1

First you have to find out where the bottle neck is.

• If it is the SSH connection, it usually does not help to open multiple connections in parallel. Better use multiple channels on one connection, if needed.

• If it is the disk IO, creating multiple threads writing (or reading) only helps if they are accessing different disks (which is seldom the case). But you could have another thread doing CPU-bound things while you are waiting on your disk IO in one thread.

• If it is the CPU, and you have enough idle cores, more threads can help. Even more, if they don't need to access common data. But still, more threads than cores (+ some threads doing IO) does not help. (Also take in mind that usually there are other processes on your server, too.)