Asymptotic optimality of bestfit for stochastic bin packing

ABSTRACT In the static bin packing problem, items of different sizes must be packed into bins or servers with unit capacity in a way that minimizes the number of bins used, and it is well-known to be a hard combinatorial problem. Best-Fit is among the simplest online heuristics for this problem. Motivated by the problem of packing virtual machines in servers in the cloud, we consider the dynamic version of this problem, when jobs arrive randomly over time and leave the system after completion of their service. We analyze the fluid limits of the system under an asymptotic Best-Fit algorithm and show that it asymptotically minimizes the number of servers used in steady state (on the fluid scale). The significance of the result is due to the fact that Best-Fit seems to achieve the best performance in practice

Scheduling Storms and Streams in the Cloud

Motivated by emerging big streaming data processing paradigms (e.g., Twitter Storm, Streaming MapReduce), we investigate the problem of scheduling graphs over a large cluster of servers. Each graph is a job, where nodes represent compute tasks and edges indicate data-flows between these compute tasks. Jobs (graphs) arrive randomly over time, and upon completion, leave the system. When a job arrives, the scheduler needs to partition the graph and distribute it over the servers to satisfy load balancing and cost considerations. Specifically, neighboring compute tasks in the graph that are mapped to different servers incur load on the network; thus a mapping of the jobs among the servers incurs a cost that is proportional to the number of "broken edges". We propose a low complexity randomized scheduling algorithm that, without service preemptions, stabilizes the system with graph arrivals/departures; more importantly, it allows a smooth trade-off between minimizing average partitioning cost and average queue lengths. Interestingly, to avoid service preemptions, our approach does not rely on a Gibbs sampler; instead, we show that the corresponding limiting invariant measure has an interpretation stemming from a loss system.Comment: 14 page