I'm running a public 1.9 server, and am also noticing the issue. I've noticed that the percentage of the allocated RAM continues to gradually climb, as though something's being cached somewhere. I've set the server to restart once an hour, which seems to clear out whatever's being cached. Some players are noticing issues with block lag around the 30 - 45 minute mark after restarts, which continues to get worse until the next scheduled restart of the server.
Confirmed in 1.10.2