Extreme lag since 1.8.1 update

Since the 1.8 update my server became very laggy. I noticed the CPU usage is extremely high. (100% most of the time) Because of the high CPU usage, the server will lag out and the watchdog will stop it. If I set the max-tick-time to -1, the server won't crash but no-one will be able to join due to the fact that there is so much lag, the connection will time out. I have included a watchdog crash log of the server and a screenshot of the linux program 'htop'. Even if I run the server on my gaming PC (much higher specs: i7 2600k, 16GB ram) the server is still very laggy. (80% CPU usage)

Can't keep up! Did the system time change, or is the server overloaded? Running 83782ms behind, skipping 1675 tick(s)