Cpu usage, tips and tricks

I'm building an O-S-C interface assuming the control of some raspberry cluster.
With some custom module that is about 500 lines and some widgets I can manage almost everything but I see my cpu usage growing at a point where I wondering if it's not too much.

Using firefox as web browser for client and node-js for running the server, I'm coming in this discussion to see if there are tricks and tips that would help to lower cpu usage on client.

Are you running the client browser and the server on the same system ?
The custom module shouldn't be a problem unless it performs tons of blocking operations (eg. read/write from disk), at least it never has been the bottleneck for me. The slowest part of o-s-c is the client, heavy sessions (with hundreds / thousands of widgets) are slower on devices with low resources.

Yes, I'm doing the test on the same system, but I'm monitoring firefox only.
I've just figured out that cpu load jumps 50% higher when the client is on edit mode.

Yes, interactions with widgets are more expensive in edit mode. Idle load should not be affected significantly though.