Characterizing C-state transitions on x86 processors

Datum

30.06.2017

Zeit

13:00 - 14:00

Sprecher

Christian Kroh

Zugehörigkeit

Institut für Technische Informatik, Professur Rechnerarchitektur

Sprache

en

Hauptthema

Informatik

Andere Themen

Informatik

Beschreibung

During recent years processor vendors have been introducing several new techniques to reduce power consumption such as dynamic voltage frequency scaling (DVFS), clock gating, and power gating. This lead to the introduction of an increasing number of processor C-states to make these innovations accessible to operating systems. The gain in power saving comes at the cost of responsiveness, since transitions to and from C-states involve a certain overhead in terms of time and energy. For applications that hold a focus on responsiveness, for example, it may be considered necessary to disable some C-states to avoid this overhead. Typically, operating systems implement their C-state control based on vendor specifications of transition latencies which can be inaccurate, as a previous paper has discussed However, the authors concentrated on the wake-up latencies of C-state transitions but did not take into account the latency on entering nor the energy consumed. To measure both, latencies and energy, during a transition, it is necessary to make a measurement infrastructure available that can capture the usage of idle states and the power consumption simultaneously. In my work, I use a patched Linux kernel and a highly sophisticated power measurement infrastructure with a high sampling rate and include measurements for both in a common infrastructure. To do so, both are collected by Score-P via an plugins for the energy measurements and one that extracts the results of the C-state transition measurements from the sysfs entries of the patched kernel. Utilizing this method I analyzed core and package C-state transitions on an Haswell E5-2690-v3 based test system with regard to different frequency settings and cache utilizations scenarios.

Letztmalig verändert: 30.06.2017, 10:02:20