Horrible locking. 95% CPU spent in spinlocks. We're still doing measurements that we'll report with all data shortly. Anyway many of them were already collected by the project; there are so many that they created a meta-issue to link to them: https://github.com/openssl/openssl/issues/17627#issuecomment...

3.1-dev is slightly less worse but still far behind 1.1.1. They made it too dynamic, and certain symbols that were constants or macroes have become functions running over lists under a lock. We noticed the worst degradation in client mode where the performance was divided by 200 for 48 threads, making it literally unusable.