FTIO: Detecting I/O Periodicity Using Frequency Techniques

Characterizing the temporal I/O behavior of an HPC application is a challenging task, but informing the system about it can be valuable for techniques such as I/O scheduling, burst buffer management, and many more, especially if provided online. In this work, we focus on the most commonly discussed temporal I/O behavior aspect: the periodicity of I/O. Specifically, we propose to examine the periodicity of the I/O phases using a signal processing technique, namely the Discrete Fourier Transform (DFT). Our approach, named FTIO, also provides metrics that quantify how far from being periodic the signal is, and hence represent yield confidence in the DFT-obtained period. We validate our approach with large-scale experiments on a productive system and examine its limitations extensively.