1. Assignment of Games to Servers in the OnLive Cloud Game System David Finkel, Mark Claypool, Sam Jaffe, Thinh Nguyen, Brendan Stephen Computer Science and Interactive Media & Game Development Worcester Polytechnic Institute Worcester, MA 01609, USA

2. Overview Worked with OnLive –thin-client, cloud-based, video game streaming service Multiple server farms User connects to nearest farm Client connects to Game Selection Portal, selects a game Connects to free server that has that game installed (a miss if game not available) 2

3. Problem Statement Server serves only one client at a time Each server has only a subset of games Question: How to assign games to servers Current method –Proportion of servers determined by expected popularity (weights) –Worst-fit algorithm to assign games to servers, respecting weights and hardware requirements 3

4. Approach Collected data from OnLive logs –Represents 1.6 million player session Fit probability distributions to data (EasyFit) Built discrete event simulation –Validated to match current operation –Re-ran with increased arrival rates Hill-climbing algorithm to minimize number of misses 4

5. How OnLive serves a client 5

6. Game Popularity 6 Pareto 2 distribution; follows Zipf’s Law

7. Interarrival Time for a Game 7 Exponential distribution, α = 0.00664.

8. Player Session Length 8 Weibull distribution, k = 0.9637 and λ = 2504.8

9. Validation Ran small-scale version, matched hand results Ran under current simulation, close to current operational results Consulted with OnLive engineers Concluded the work OnLive originally proposed 9

10. Optimization Used simulation to improve assignment of games to servers Increased arrival rate up to 7x current Used hill-climbing algorithm to improve weights (proportion of servers with a particular game) Obtained reduced disk space requirements 10

11. Hill-Climbing Algorithm 11 step size 5% while (not all game weights are locked) for (each game) if (game does not have misses) decrease weight by one step elseif (game has been decreased already) increase weight by one step lock game weight else increase weight by one step Re-run simulation with new weights

12. Number of misses 12 Hill-climbing and current OnLive operation virtually identical

13. Disk space utilization 13 Disk space utilization on different servers

14. Advantages of saving disk space Cost saving over large number of servers Faster installation of games Faster reconfiguration Changing games configurations expensive –Future: Design re-configurations to minimize costs 14