When configured to trigger PR builds when an upstream branch changes, if there is hundreds of PRs open, the Jenkins Master fires the initial checkout to get the Jenkinsfile all at the same time on the master.

This means literally, that several hundred git operations get called at the same time, stressing out the file system on the master to the point that the master stops responding.  Especially when that repository is very large.  It also puts tremendous load on the upstream Bitbucket server, which starts throttling at a certain point.  Even with reference repositories in use.

It seems that there needs to be a configuration option to control how many of these git operations are allowed to fire on the master at the same time.

This effectively brings down our Jenkins master daily.