Phoronix published a review on the The Performance Impact Of Linux Disk Encryption On Ubuntu 14.04 LTS
A quote from the article:
For any Linux laptop users or those concerned about their data's safety on production systems, I highly recommend utilizing disk encryption for safeguarding the data. However, what's the performance impact like these days? In this article with the current development snapshot of Ubuntu 14.04 LTS on a modern Intel ultrabook we're looking at the impact (including CPU utilization) of using an eCryptfs-based home directory encryption and LUKS-based full-disk encryption on Ubuntu Linux.The Performance Impact Of Linux Disk Encryption On Ubuntu 14.04 LTS @ Phoronix