Jenkins crashing frequently. Jenkins suddenly crashing frequently when building jobs. Jenkins becoming very slow. You have performance plugin installed on your instance.
The Performance plugin generates graphs of JMeter and other performance analysis data, which can then be viewed in the Jenkins UI. When dealing with large datasets this plugin is known to cause performance issues. In some previous instances we’ve seen evidence that memory usage on the controller spikes up to the heap limit, and then it gets stuck in a cycle of full GCs which effectively stop the application completely. When the Performance plugin generates graphs, it is suddenly consuming all the heap memory on the controller, causing it to effectively crash. The main culprit is the URIReport which by default shows all samples of test, this causes issues when running large number of tests.
If you face similar issues it is suggested to disable the plugin. See How to disable a plugin when Jenkins is down? on how to disable a plugin in Jenkins.