Put the summary of the bug you're having here

What I expected to happen was...:
Describe what you thought should happen here

What actually happened was...:
Once the server is started the amount of lag increases over time and it becomes practically unplayable. The last snapshot that would not have this kind of lag is 15w47c. Following is a partial printout of the console:

06.02 19:50:39 [Server] INFO Using : vl@22c3045f
06.02 19:50:39 [Server] INFO Not using : vl@30c3001d
06.02 19:50:38 [Server] INFO Not using : vl@21a5dccc
06.02 19:50:38 [Server] INFO Not using : vl@491b55eb
06.02 19:50:38 [Server] INFO Not using : vl@23ebba69
...

Im not sure if the vl@xxxxxxx thing is a problem or not because i have not seen that in the past.
Thx for your help.