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Power Issues in On-chip Interconnection Networks. Mojtaba Amiri Nov. 5, 2009. Why Interconnection Networks?. Interconnection Networks Issues. Performance, Reliability Power Consumption. Papers.
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Power Issues in On-chip Interconnection Networks MojtabaAmiri Nov. 5, 2009
Interconnection Networks Issues • Performance, Reliability • Power Consumption
Papers • PowerHerd: A distributed scheme for dynamic satisfying peak power constraints in interconnection networks • Dynamic voltage scaling with links for power optimization of interconnection networks By L. Shang, L.-S. Peh, and N. K. Jha ECE, University of Princeton
PowerHerd: A Distributed Scheme for Dynamically Satisfying Peak-Power Constraints in Interconnection Networks • By • L. Shang, L.-S. Peh, and N. K. Jha • Department of Electrical Engineering • Princeton University
Introduction (1) • Problem • Peak-power constrains • Solution • PowerHerd • Distributed and run-time • Modified router
Introduction (2) • An Example
PoweHerd Router Mechanism PLPB =PGPB/# Routers Estimate PLPB Predict PLPB Calculate Shared power Update routing decision Throttle switch allocator Negotiation with neighbors and share power Update PLPB
Dynamic Power Estimation • Power dominators: • Input Buffer • Crossbar Switch • Link Based on Switching activity, Number, Coefficients from linear regression
Estimation Error • Orion error 2-3% Total 10%
Leakage Power Estimation • Based on • Switching activity, • Number, • Coefficients from linear regression • Leakage Power is about 10%. (Critique)
Dynamic Power Prediction • W around 4 3 Hardware Simplification • By shift and add
Dynamic Power Throttling • Near the local power budget • Simple gating (Critique)
Power-aware Routing • Previous routing algorithms • Performance • Fault-tolerance • This routing algorithm considers power consumption of neighbors • Low overhead
Result Comparison-StaticAllocPower 136.3 W Global Power budget 27.3 W
Effect of Power-Sharing Interval 136.3 W Global Power budget 53.3W
Effect of Local Power Constraints PGPB = 136.3 W
Summary • PowerHerd • Distributed Scalable • Online (Dynamic) Efficient • Guarantee Peak-Power Constrain The Issue • Help other techniques
Dynamic Voltage Scaling with Links for Power Optimization of InterconnectionNetworks • By • L. Shang, L.-S. Peh, and N. K. Jha • Department of Electrical Engineering • Princeton University
Introduction • Power saving technique • Employs DVFS Links (the first attempt) • How? Based on history of previous actions • Performance penalty • 2.5 throughput • 15.2 average latency
DVFS Link • Characteristics of a DVFS link • Transition time (100 link clock cycles) • Transition energy • Transition status • Transition step C= 5us n = .9
Communication Traffic Charc. Link Utilization (LU) What is the Problem with this model? Congestion
CTC- Input Buffer Utilization Congestion
Input Buffer Age Congestion
Prediction Policy • LU & BU together is enough • DVFS based on two steps • First Link Utilization • Second congestion • Simple Implementation
Effect of DVFS links with varying Char. 1ms Task Duration 0.1 us
Summary • Appling DVFS to Interconnection networks • History-based DVFS (LU, BU) • Power saving HUGH! • First study
Critiques to PoweHerd • Consider static power 10% now is much more! • Gate-level design for traffic throttling is not realistic. • Completely Distributed; suggestion hybrid!
Critiques to DVFS Link • There is no 100% guarantee to find the optimum for History-Based Policy • This method works because the link is supposed to be power dominator! Inconsistent with first paper.
