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An Analysis of Efficient Multi-Core Global Power Management Policies: Maximizing Performance for
a Given Power Budget
Represented by: Majid Malaika
Authors: Canturk Isci†, Alper Buyuktosunoglu†, Chen-Yong Cher†, Pradip Bose† and Margaret Martonosi
Computer Science and Engineering
Agenda
Background Motivation Contribution Overview of the global power management policy Core Power Modes Global Power Management Policies Independent Per-Core Power Management Simulation Evaluation Q&A
Computer Science and Engineering
Background
Power Management are desired for many reasons: For portable devices For Desktop systems For Supercomputers
P = V^2 * F Power is proportional to voltage squared Current is also proportional to voltage
Computer Science and Engineering
Cont. Background
Multicore architecture has become more important than ever due to the Famous “Walls”
With more cores on the dice, Power and temperature problems are becoming more and more crucial
Computer Science and Engineering
Motivation
How to enforce a power budget through global power manager? How to minimize power given a performance target?
Computer Science and Engineering
Contributions
Introduced the concept of Global Power Manager (PM) Developed a fast static power management analysis tool Evaluated different PM policies (with different focus such as
prioritization, fairness, throughput)
Computer Science and Engineering
Global CMP Power Management Overview
To exploit the widely known variability in demand and characteristics of the input workloads
Adaptive response to “Phases” for power-efficient computing.
Computer Science and Engineering
Cont. Global CMP Power Management Overview
the loop of PM’s work PM periodically collects power-performance data from local monitors PM reports it to OS OS returns power budget, thread affinities, high-level scheduling and
load-balancing plan to PM PM decides the power-mode of each core based on those info
Computer Science and Engineering
Cont. Global CMP Power Management Overview
Preconditions Each core has its own dynamic controller has its power-performance monitor (e.g. current monitor,
perf monitoring counter hw) can be running in multiple power modes
Computer Science and Engineering
Core Power Modes
Three Power Modes: Turbo Efficient1(Eff1) Efficient2(Eff2)
The target is to achieve
PowerSavings : PerformanceDegradation ratio of 3 : 1
Computer Science and Engineering
Cont. Core Power Modes
Transition overhead between Power Modes The duration of each monitored interval is called “Explore
time” and is set to 500 MS. Low overhead (1 to 4%)
Computer Science and Engineering
Global Power Management Policies
Introduced three policies for different objectives:
Priority PullhiPushLo MaxBIPS
Computer Science and Engineering
Cont. Global Power Management Policies
Priority Assigns Different Priority to different tasks Highest Priority to highest Core (Example Core4) Lowest Priority to Lowest Core (Example Core1) In policy implementation it tries to run the highest AFAP Prefer to slow down the first core in case of budget
overshoot
Computer Science and Engineering
Cont. Global Power Management Policies
PullhiPushLo Tries to balance the power consumption of each core It slows down the highest core in case of a budget
overshoot And by speeding up the lowest power core when there
is available
Computer Science and Engineering
Cont. Global Power Management Policies
MaxBIPS Targets at optimizing the system throughput Predicts and choose the Power Mode that Maximizes
the throughput at each explore time
MaxBIPS does that by predicting the corresponding power and BIPS values for each power mode
It then chooses the combination with the highest throughput that satisfies the current power budget
Computer Science and Engineering
Independent Per-Core Power Management
Chip-Wide DVFS Simpler alternative No Synchronization across cores Simplified OS and Hardware All cores transition together into Turbo, Eff1, Eff2 at
each explore time based on budget constraints
Computer Science and Engineering
Simulation
Based on IBM Turandot simulator Power statistics from IBM PowerTimer The list of core parameter
Computer Science and Engineering
References
C. Isci et al., "An Analysis of Efficient Multi-Core Global Power Management Policies: Maximizing Performance for a Given Power Budget"