CSE 691: Energy-Efficient ComputingLecture 7

SMARTS: custom-made systemsAnshul Gandhi

1307, CS buildinganshul@cs.stonybrook.edu

memcache

Benchmark competitions

Benchmark competitions

fawn paper

Data-intensive workloads

Seek-bound• small• random

• examples?• problems?

Scan-bound• large• sequential

• examples?• problems?

Why FAWN?

1. Memory wall (??)

2. Increased CPU power consumption

3. DVFS is limited

• Modern CPUs operate close to Vmin

• Constant leakage current

4. Peak power and data center density

FAWN results

Processor scaling trends

1. Moore’s law (observation)• # transistors/chip ↑ 2X/2yr (how?)• Frequency ↑ as transistor size ↓ (max 9GHz)

• Leakage current/power ↑ as transistor size ↓• Heat ↑ as frequency ↑

Processor scaling trends

2. Dennard scaling (observation)• Transistor power (V+I) ↓ as transistor size ↓• + Moore’s law = perf/watt ↑ 2X/2yr (how?)

• Not true now due to leakage current

• So we did multicore!

heteromates paper

Dark silicon

• Cannot power on all of the CPU• Result of:

1. Success of Moore’s law2. Failure of Dennard scaling

• Turbo boost

Main ideas

• Heterogeneous cores1. For different performance requirements2. Energy considerations (battery vs. plugged)3. Thermal considerations4. Dark silicon

Main ideas

Main ideas