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To get a more specific answer you'll need to provide a lot more information about how to reproduce your issue. In particular you need to understand how any specific component is integrated into the larger system.

Questions that would be helpful for improving performance.

• Are you running the nodelets in the same process?
• Is there other nodelets running?
• How many threads are available in the nodelet manager? How many do you expect used at any given time?
• Are you CPU constrained?
• What else is running on the system?
• What else is publishing or subscribing in the node on the system?

If you can also get 0ms latency that suggests that it can go quickly. And then the question is why is it sometimes not delivering it quickly in other cases.

My speculation guessing at many of the answers to the above question is that you're callback queue is being starved for threads/processing time when you get the large latency numbers. When resources are exhausted we have many ways to gracefully degrade. Everything is queued etc, and if queues overflow content will get dropped. Adding a large processing load in other callbacks can starve other callbacks in the queue etc.