Title: TRINITY: Coordinated Performance, Energy and Temperature Management in 3D Processor-Memory Stacks,
Abstract: The consistent demand for better performance has lead to innovations at
hardware and microarchitectural levels. 3D stacking of memory and logic dies
delivers an order of magnitude improvement in available memory bandwidth. The
price paid however is, tight thermal constraints.
In this paper, we study the complex multiphysics interactions between
performance, energy and temperature. Using a cache coherent multicore processor
cycle level simulator coupled with power and thermal estimation tools, we
investigate the interactions between (a) thermal behaviors (b) compute and
memory microarchitecture and (c) application workloads. The key insights from
this exploration reveal the need to manage performance, energy and temperature
in a coordinated fashion. Furthermore, we identify the concept of "effective
heat capacity" i.e. the heat generated beyond which no further gains in
performance is observed with increases in voltage-frequency of the compute
logic. Subsequently, a real-time, numerical optimization based, application
agnostic controller (TRINITY) is developed which intelligently manages the
three parameters of interest. We observe up to $30\%$ improvement in Energy
Delay$^2$ Product and up to $8$ Kelvin lower core temperatures as compared to
fixed frequencies. Compared to the \texttt{ondemand} Linux CPU DVFS governor,
for similar energy efficiency, TRINITY keeps the cores cooler by $6$ Kelvin
which increases the lifetime reliability by up to 59\%.