Abstract Storage stack layers in high-performance computing (HPC) systems offer many tunable parameters controlling I/O behaviors and underlying file system settings. The setting of these parameters plays a decisive role in I/O performance. Nevertheless, the increasing complexity of data operations and storage architectures makes identifying a set of well-performing configurations a challenge. Auto-tuning is a promising technology. This paper presents a comprehensive survey on "Auto-tuning in HPC I/O". We expound a general storage structure based on a general storage stack and critical elements of auto-tuning, and categorize related studies according to the way of tuning. On the basis of the order in which the approaches were applied, we introduce the specific works of each approach in detail, and summarize and compare the pros and cons of these approaches. Through a comprehensive and in-depth study of existing research, we elaborate on the development history of auto-tuning technology in HPC I/O, analyze the current situation, and provide guidance for optimization technology in the future.

Concurrent programs are normally composed of multiple concurrent threads sharing memory space. These threads are often interleaved, which may lead to some non-determinism in execution results, even for the same program input. This poses huge challenges to the testing of concurrent programs, especially on the test result verification—that is, the prevalent existence of the oracle problem. In this article, we investigate the application of metamorphic testing (MT), a mainstream technique to address the oracle problem, into the testing of concurrent programs. Based on the unique features of interleaved executions in concurrent programming, we propose an extended notion of metamorphic relations, the core part of MT, which are particularly designed for the testing of concurrent programs. A comprehensive testing approach, namely ConMT , is thus developed and a tool is built to automate its implementation on concurrent programs written in Java. Empirical studies have been conducted to evaluate the performance of ConMT, and the experimental results show that in addition to addressing the oracle problem, ConMT outperforms the baseline traditional testing techniques with respect to a higher degree of automation, better bug detection capability, and shorter testing time. It is clear that ConMT can significantly improve the cost-effectiveness for the testing of concurrent programs and thus advances the state of the art in the field. The study also brings novelty into MT, hence promoting the fundamental research of software testing.

Developing correct multi-threaded programs is challenging and concurrency bugs can be easily introduced. Many of them, known as concurrency vulnerabilities, can be exploited to launch attacks. Fuzzing is shown to be a practical and effective technique to expose vulnerabilities. However, existing works on fuzzing concurrency vulnerabilities almost all follow the framework (like AFL++) designed for fuzzing sequential vulnerabilities. Unlike sequential vulnerabilities, concurrency ones cannot be easily triggered. Concurrency vulnerabilities rely on both inputs and thread interleaving to be exposed while existing fuzzing techniques mainly focus on how to generate effective inputs. We present a new framework based on an existing fuzzing technique, AFL++, to integrate the predictive techniques for effective concurrency vulnerability detection. For every input (the original and the mutated ones), we call a predictive tool such that, even if a concurrency vulnerability is not really triggered, it can be predicted. To overcome heavy efficiency challenges existing in predictive tools, we propose to selectively call a predictive tool based on concurrency coverage criteria. We have selected a sound predictive tool SeqCheck and adapted it to propose our fuzzing framework PredFuzz. We compared our tool with two tools, AFL++ integrated with Google ThreadSanitizer and AFL++ directly integrated with SeqCheck, on six previously studied multi-threaded programs. The experimental results showed that PredFuzz detected significantly more vulnerabilities than AFL++ integrated with ThreadSanitizer and about 70% vulnerabilities detected by AFL++ directly integrated with SeqCheck. Besides, it is extremely efficient without compromising the fuzzing speed of AFL++: it added a smaller slowdown to AFL++ than ThreadSanitizer did and achieved a speedup of more than 1,000x when compared to AFL++ directly integrated with SeqCheck.

Concurrency bugs are extremely difficult to detect. Recently, several dynamic techniques achieve sound analysis. M2 is even complete for two threads. It is designed to decide whether two events can occur consecutively. However, real-world concurrency bugs can involve more events and threads. Some can occur when the order of two or more events can be exchanged even if they occur not consecutively. We propose a new technique SeqCheck to soundly decide whether a sequence of events can occur in a specified order. The ordered sequence represents a potential concurrency bug. And several known forms of concurrency bugs can be easily encoded into event sequences where each represents a way that the bug can occur. To achieve it, SeqCheck explicitly analyzes branch events and includes a set of efficient algorithms. We show that SeqCheck is sound; and it is also complete on traces of two threads.

Modern network research and operations are inseparable from network testers to evaluate performance limits of proofs-of-concept, troubleshoot failures, etc. Existing network testers suffer from either constrained flexibility or a low performance-cost ratio. In this paper, we propose a new network tester, HyperTester. The core of HyperTester is to leverage new-generation programmable switches for generating and capturing test traffic with high performance, low cost, and remarkable flexibility. We design a series of efficient mechanisms, including template-based packet generation, false-positive-free counter-based queries, and stateless connections to realize various network testing tasks upon switches with limited programmability and resources. Meanwhile, to facilitate developing testing tasks upon HyperTester, we provide a high-level network testing API. We have implemented HyperTester on the Tofino switch and built dozens of network testing tasks. The evaluations on the hardware testbed show that HyperTester supports line-rate packet generation (400Gbps in the testbed) with highly-accurate rate control, while HyperTester can save $40150 per Tps and 9225W per Tbps when compared with the software network testers.