(Info gathered from other sources, Joev, [HK]Heretic, and this topic: http://www.unknownworlds.com/forums/in...ST&f=33&t=42107 )
Problem: When running HLDS 3.1.1.1 and NS (or other mods) , linux servers may have very high utilization on the HLDS process.
Recommended workaround: Revert to HLDS 3.1.1.0 (and apply solution from here: http://www.unknownworlds.com/forums/in...=ST&f=8&t=40291 to avoid possible security risks). This high utilization also occurs in mods like DOD and CS, but since their servers have very little to keep track of, the manifestation of high CPU is not as bad. NS is naturally a much more complex server process due to the gameplay itself.
Hpefully Valve is working on something to fix this issue with 3.1.1.1 - we have no real control over this though. As you can see when 2.0 is run on 3.1.1.0, your utilization will be signifigantly lower in all mods, including NS.