AgilePkgC: An Agile System Idle State Architecture for Energy Proportional Datacenter Servers

TL;DR

This paper introduces AgilePkgC, a new C-state architecture that significantly reduces energy consumption in datacenter servers during idle periods with minimal performance impact.

Contribution

The paper proposes a novel hardware-supported C-state architecture, AgilePkgC, that enables fast transitions and substantial power savings for idle server resources.

Findings

Potential to reduce server power by up to 41%.

Achieves less than 0.1% performance degradation.

Supports adoption of deep, fast package C-states.

Abstract

This paper presents the design of AgilePkgC (APC): a new C-state architecture that improves the energy proportionality of servers that operate at low utilization while running microservices of user-facing applications. APC targets the reduction of power when all cores are idle in a shallow C-state, ready to transition back to service. In particular, APC targets the power of the resources shared by the cores (e.g., LLC, network-on-chip, IOs, DRAM) which remain active while no core is active to use them. APC realizes its objective by using low-overhead hardware to facilitate sub-microsecond entry/exit latency to a new package C-state and judiciously selecting intermediate power modes for the different shared resources that offer fast transition and, yet, substantial power savings. Our experimental evaluation supports that APC holds the potential to reduce server power by up to 41% with a worst-case performance degradation of less than 0.1% for several representative workloads. Our results clearly support the research and development and eventual adoption of new deep and fast package C-states, like APC, for future server CPUs targeting datacenters running microservices.