Adaptive Power Shifting in Server Systems Ming Chen Xue Li

Introduction  Power is one of the most important resources in data centers.  CPU and main memory are two of the largest power gluttons. 85.4% 92.2% CPU & memCPU : mem

Motivation  Power is a limited and precious resource for a server.  CPU is NEITHER the only, NOR the largest consumer.  Power needs to be controlled within a budget.  Workload is varying in data centers.  Over-provisioning may cause unnecessary cost.  Power needs to be optimally allocated among server components, i.e., CPU and main memory. Goal: 1. Power control in the server-level. 2. Optimized allocation between CPU and main memory.

State of The Art  Power control for CPU [Wang] in ISCA’09, main memory [Diniz] in ISCA’07 − Single component;  Power control for servers [Lefurgy] in ICAC’07 − Assuming CPU is the major consumer  Power shifting in server-level [Felter] in ICS’05 − Power is not controlled at the budget. − Performance is not optimal.  Power control for racks [Wang] in HPCA’08, data centers [Wang] in PACT’09 − Complimentary to that work − Compose a complete power management scheme for data centers.

Who is Waiting? CPU mem CPU mem CPU mem CPU mem CPU mem CPU mem CPU is waiting.Memory is waiting.Coordinated.  CPU: DVFS  Memory: active memory size -> bandwidth

 CPU-intensive workload  Power should be shifted to CPU as much as possible.  f opt = f max  Memory-intensive workload  Power should be shifted to memory as much as possible.  f opt = f min  Memory-intensive workload.  f opt = ? What is the optimal allocation? For any piece of codes, it belongs to one of the following cases:

Proposed Solution − Ratio of the two weights: Memory Access Rate (MAR) − Optimization Weights the # of dispatched instructions in each control period the # of memory access requests in each control period  Intuition − The more the # of activities is, the more power is required.  Problems − MAR can guarantee the optimal allocation? − The weight ratio should be a function of MAR?  Solution: − Power is controlled at the budget.

Schedules  Idea verification (by the end of Sept) − Simulators integration; −Preliminary experiments to show the idea works;  Controller design and tuning (by Oct 20) − Refinement of the idea − Refinement of sleeping scheme − Experiment plan  Experiments and paper writing (until middle of Nov)