Re^3: Using threads to run multiple external processes at the same time

It could be one (or a combination of) several factors:

Are you passing small messages from your worker threads to your "manager" thread, or are you passing large chunks of data?
How often are you passing messages from your worker threads to your manager thread? Can you reduce the frequency that this occurs?
Can you add more threads?

Comment on Re^3: Using threads to run multiple external processes at the same time