Power consumption management in fat-tree interconnection networks

• Novel mechanism for reducing power consumption in fat-trees.
• Flexible mechanism that can be tuned in terms of aggressiveness and sensitivity.
• Simple implementation: same routing algorithm regardless of the power saving level.
• Ability of the mechanism to provide very significant power savings.
• Light impact in latency while providing always favorable energy balance.

As higher communication bandwidth is required in current designs of high performance parallel computers, the amount of power consumed by the interconnection network also increases. Fat-tree is one of the most popular topologies in high performance interconnection networks aiming at low latency, efficient collective communication and scalability. We present a new methodology for managing power consumption of fat-tree interconnection networks. Our proposal is based on dynamically adjusting available network bandwidth according to traffic requirements. To meet this goal, we define a mechanism for managing the operating status of network links as a function of network load. Our main contributions include a complete definition of the mechanism and a tuning methodology based on its sensitivity and aggressiveness in terms of potential power savings. Results show that our proposal can provide significant power savings (up to 67% in a 4-ary 4-tree) with no changes in the underlying routing algorithm, with minimal impact on network performance. Experiments conducted on a 16-ary 3-tree topology provide up to 36% energy savings with performance degradation below 1.10%.