Power Issues in On-chip Interconnection Networks Mojtaba Amiri Nov. 5, 2009
2 ECE
3 – Performance, Reliability – Power Consumption
4 ECE 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
By L. Shang, L.-S. Peh, and N. K. Jha Department of Electrical Engineering Princeton University
6 ECE Problem Peak-power constrains Solution PowerHerd – Distributed and run-time – Modified router
7 ECE – An Example
8 ECE
9 P LPB =P GPB /# Routers Estimate P LPB Predict P LPB Calculate Shared power Negotiation with neighbors and share power Update P LPB Throttle switch allocator Update routing decision
10 ECE Power dominators: – Input Buffer – Crossbar Switch – Link Based on Switching activity, Number, Coefficients from linear regression
11 ECE Orion error 2-3% Total 10%
12 ECE Leakage Power is about 10%. (Critique) Based on Switching activity, Number, Coefficients from linear regression
13 ECE W around 4 3 Hardware Simplification By shift and add
14 ECE T GPB /N
15 ECE /2
16 ECE Near the local power budget Simple gating (Critique)
17 ECE Previous routing algorithms – Performance – Fault-tolerance This routing algorithm considers power consumption of neighbors – Low overhead
18 ECE
19 ECE Global Power budget Global Power budget W 27.3 W
20 ECE Global Power budget Global Power budget W 53.3W
21 ECE P GPB = W
22 ECE
23 ECE PowerHerd – Distributed Scalable – Online (Dynamic) Efficient – Guarantee Peak-Power Constrain The Issue – Help other techniques
By L. Shang, L.-S. Peh, and N. K. Jha Department of Electrical Engineering Princeton University
25 ECE 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
26 ECE C= 5us n =.9 C= 5us n =.9 Characteristics of a DVFS link – Transition time (100 link clock cycles ) – Transition energy – Transition status – Transition step
27 ECE Link Utilization (LU) Congestion What is the Problem with this model?
28 ECE Congestion
29 ECE Congestion
30 ECE LU & BU together is enough DVFS based on two steps First Link Utilization Second congestion Simple Implementation
31 ECE
32 ECE
33 ECE
34 ECE Task Duration Task Duration 1ms 0.1 us
35 ECE Appling DVFS to Interconnection networks History-based DVFS (LU, BU) Power saving HUGH! First study
36 ECE Consider static power 10% now is much more! Gate-level design for traffic throttling is not realistic. Completely Distributed; suggestion hybrid!
37 ECE 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.
38 ECE PowerHerdDVFS Link TargetPeak Power ConstrainPower Consumption Performance PenaltyYes Power TechniquePower –aware routing, Dynamic power throttling DVFS Improvement100% guarantee6 times saving Inconsistent Assumptions (most power dominator) Input BuffersLinks