concurrency program design stackless python tasklet or python thread?

[davy zhang]

first here is my basic idea is every actor holds their own msg queue,
the process function will handle the message as soon as the dispatcher
object put the message in.

This idea naturally leads me to place every actor in a separate thread
waiting for msg

but the rumor has it, stackless python with tasklet and channel can do
much more better in concurrency program, so I dive my head into it.

but I found the tasklet is really a lined-up sequence , that means if
a tasklet blocked or do some time consuming calculation, the other
tasklets can not get the cpu slice

so we must design very carefully to avoid the big job for single task

I am just confused why the stackless python is said to be good at
concurrency program model or just I get a wrong idea to practice?