Image processing and performance

[gvarndell]

Originally Posted by ellisk

I'm using threads ("tasks" on the cRIO) for the different parts of our code, and there's currently 3 threads. I'm wondering if the threads are all getting 1/3 of the CPU, and so that's slowing down our code. Is that possible?

It's possible but not likely. The vxWorks kernel doesn't schedule tasks for a fixed length of time. If it did, and there were only 3 tasks, then each would 'use' approximately 1/3 of the CPU time. Under vxWorks, tasks are made ready by events and the highest priority ready task is scheduled to run. That task will run until a) it relinquishes control or b) is preempted by a higher priority task becoming ready. (think about the implications of a high priority task that doesn't relinquish control)

Originally Posted by ellisk

can I set the priority of some threads to be higher? I noticed in the constructor for the Task class that I can specify a priority (it defaults to 100). Is 1 the highest or 100?

Yes. You can do so before the task is created or any time after.
The highest priority is 0 -- 255 is the lowest.
Take my word for this, you don't want to use a priority higher than 51 for your robot tasks unless you know exactly what you're doing.

Originally Posted by ellisk

How can I set the priority of the thread which runs OperatorControl?

If you can get hold of the 'object' for that task, then yes.
Just call the SetPriority method.
I'm neither a C++ fan nor a C++ expert, so I can't tell you how to 'get' a task object for a task your didn't 'instantiate'.
Note that you can create tasks and do whatever you like with them, in a less obfuscated way, by simply calling the vxWorks taskLib API.