The class sun.security.ssl.SSLSessionContextImpl maintains caches for the sessions reuse.
Access to the cache from threads is serialized.
It was reported that under heavy load the time of waiting for the turn to access the synchronized methods overweights the time of creating a new session.

Currently there's no way to avoid using the cache.
A new flag should be introduced that would allow to avoid using the cache and thus avoid the bottleneck.