Workload Characterization

• A Deep Look into the Temporal I/O Behavior of HPC Applications

  Francieli Boito, Luan Teylo, Mihail Popov, Théo Jolivel, François Tessier, Jakob Luettgau, Julien Monniot, Ahmad Tarraf, André Carneiro, Carla Osthoff June 2025 - IPDPS 2025 - Conference Paper Abstract: The increasing gap between compute and I/O speeds in high-performance computing (HPC) systems imposes the need for techniques to improve applications' I/O performance. Such techniques must rely on assumptions about I/O behavior in order to efficiently allocate I/O resources such as burst buffers, to schedule accesses to the shared parallel file system or to delay certain applications at the batch scheduler level to prevent contention, for instance. In this paper, we verify these common assumptions about I/O behavior, specifically about temporal behavior, using over 440,000 traces from real HPC systems. By combining traces from diverse systems, we characterize the behaviors observed in real HPC workloads. Among other findings, we show that I/O activity tends to last for a few seconds, and that periodic jobs are the minority, but responsible for a large portion of the I/O time. Furthermore, we make projections for the expected improvement yielded by popular approaches for I/O performance improvement. Our work provides valuable insights to everyone working to alleviate the I/O bottleneck in HPC.