On System Noise and Large-scale Parallel Applications

Datum

26.05.2011

Zeit

15:00 - 16:00

Sprecher

Torsten Höfler

Zugehörigkeit

University of Illinois, USA

Serie

TUD ZIH Kolloquium

Sprache

en

Hauptthema

Informatik

Andere Themen

Mathematik, Informatik

Host

Ralf Müller-Pfefferkorn

Beschreibung

System noise is increasingly a concern as HPC systems continue to grow in scale. This talk presents an in-depth analysis of the impact of system noise on large-scale parallel application performance in realistic settings. We present a model-based simulation toolchain that uses the LogGOPS model and Lamport's clock condition to inject noise delays from traces into complex communication relations. We show that the number of processes at which noise becomes a significant bottleneck is system-specific and depends more on the structure of the noise than its intensity. In contrast to previous studies, we show that not only collective operations but also point-to-point communications influence the application's sensitivity to noise. We also discuss the influence of noise-mitigation strategies, for example, our results verify the long-standing conjecture that co-scheduling prevents significant application slowdown. We discovered that the noise bottleneck can lead to a 100x slowdown of single collective operations and a 2x slowdown of scientific applications on very large-scale systems. Our developed tools can be utilized quantify this noise bottleneck and to tune the noise signatures of systems and applications for minimal noise propagation.

Letztmalig verändert: 26.05.2011, 14:07:04