akougkas.io

Large-scale data analytics, scientific simulation, and deep learning codes in HPC perform massive computations on data greatly exceeding the bounds of main memory. These out-of-core algorithms suffer from severe data movement penalties, programming complexity, and limited code reuse. To solve this, HPC sites have steadily increased DRAM capacity. However, this is not sustainable due to financial and environmental costs. A more elegant, low-cost, and portable solution is to expand memory to distributed multitiered storage. In this work, we propose MegaMmap: a software distributed shared memory (DSM) that enlarges effective memory capacity through intelligent tiered DRAM and storage management. MegaMmap provides workload-aware data organization, eviction, and prefetching policies to reduce DRAM consumption while ensuring speedy access to critical data. A variety of memory coherence optimizations are provided through an intuitive hinting system. Evaluations show that various workloads can be executed with a fraction of the DRAM while offering competitive performance.

Traditionally, I/O systems have been developed within the confines of a centralized OS kernel. This led to monolithic and rigid storage systems that are limited by low development speed, expressiveness, and performance. Various assumptions are imposed including reliance on the UNIX-file abstraction, the POSIX standard, and a narrow set of I/O policies. However, this monolithic design philosophy makes it difficult to develop and deploy new I/O approaches to satisfy the rapidly-evolving I/O requirements of modern scientific applications. To this end, we propose LabStor: a modular and extensible platform for developing high-performance, customized I/O stacks. Single-purpose I/O modules (e.g, I/O schedulers) can be developed in the comfort of userspace and released as plug-ins, while end-users can compose these modules to form workload- and hardware-specific I/O stacks. Evaluations show that by switching to a fully modular design, tailored I/O stacks can yield performance improvements of up to 60% in various applications.

Deep learning has been shown as a successful method for various tasks, and its popularity results in numerous open-source deep learning software tools. Deep learning has been applied to a broad spectrum of scientific domains such as cosmology, particle physics, computer vision, fusion, and astrophysics. Scientists have performed a great deal of work to optimize the computational performance of deep learning frameworks. However, the same cannot be said for I/O performance. As deep learning algorithms rely on big-data volume and variety to effectively train neural networks accurately, I/O is a significant bottleneck on large-scale distributed deep learning training. This study aims to provide a detailed investigation of the I/O behavior of various scientific deep learning workloads running on the Theta supercomputer at Argonne Leadership Computing Facility. In this paper, we present DLIO, a novel representative benchmark suite built based on the I/O profiling of the selected workloads. DLIO can be utilized to accurately emulate the I/O behavior of modern scientific deep learning applications. Using DLIO, application developers and system software solution architects can identify potential I/O bottlenecks in their applications and guide optimizations to boost the I/O performance leading to lower training times by up to 6.7x.

In the era of data-intensive computing, large-scale applications, in both scientific and the BigData communities, demonstrate unique I/O requirements leading to a proliferation of different storage devices and software stacks, many of which have conflicting requirements. In this paper, we investigate how to support a wide variety of conflicting I/O workloads under a single storage system. We introduce the idea of a Label, a new data representation, and, we present LABIOS: a new, distributed, Label- based I/O system. LABIOS boosts I/O performance by up to 17x via asynchronous I/O, supports heterogeneous storage resources, offers storage elasticity, and promotes in-situ analytics via data provisioning. LABIOS demonstrates the effectiveness of storage bridging to support the convergence of HPC and BigData workloads on a single platform.

Modern High-Performance Computing (HPC) systems are adding extra layers to the memory and storage hierarchy named deep memory and storage hierarchy (DMSH), to increase I/O performance. New hardware technologies, such as NVMe and SSD, have been introduced in burst buffer installations to reduce the pressure for external storage and boost the burstiness of modern I/O systems. The DMSH has demonstrated its strength and potential in practice. However, each layer of DMSH is an independent heterogeneous system and data movement among more layers is significantly more complex even without considering heterogeneity. How to efficiently utilize the DMSH is a subject of research facing the HPC community. In this paper, we present the design and implementation of Hermes: a new, heterogeneous-aware, multi-tiered, dynamic, and distributed I/O buffering system. Hermes enables, manages, supervises, and, in some sense, extends I/O buffering to fully integrate into the DMSH. We introduce three novel data placement policies to efficiently utilize all layers and we present three novel techniques to perform memory, metadata, and communication management in hierarchical buffering systems. Our evaluation shows that, in addition to automatic data movement through the hierarchy, Hermes can significantly accelerate I/O and outperforms by more than 2x state-of-the-art buffering platforms.

Concurrent accesses to the shared storage resources in current HPC machines lead to severe performance degradation caused by I/O contention. In this study, we identify some key challenges to efficiently handling interleaved data accesses, and we propose a system-wide solution to optimize global performance. We implemented and tested several I/O scheduling policies, including prioritizing specific applications by leveraging burst buffers to defer the conflicting accesses from another application and/or directing the requests to different storage servers inside the parallel file system infrastructure. The results show that we mitigate the negative effects of interference and optimize the performance up to 2x depending on the selected I/O policy.