@misc {42839,
	title = {Deliberate Microbenchmarking of Software Systems},
	howpublished = {Cancer Registry of Norway},
	year = {2021},
	type = {Seminar Talk},
	abstract = {In this talk, I will summarize the findings of my PhD thesis:Software performance faults have severe consequences for users, developers, and companies. One way to unveil performance faults before they manifest in production is performance testing, which ought to be done on every new version of the software, ideally on every commit. However, performance testing faces multiple challenges that inhibit it from being applied early in the development process, on every new commit, and in an automated fashion.In this dissertation, we investigate three challenges of software microbenchmarks, a performance testing technique on unit granularity which is predominantly used for libraries and frameworks. The studied challenges affect the quality aspects (1) runtime, (2) result variability, and (3) performance change detection of microbenchmark executions. The objective is to understand the extent of these challenges in real-world software and to find solutions to address these.To investigate the challenges{\textquoteright} extent, we perform a series of experiments and analyses. We execute benchmarks in bare-metal as well as multiple cloud environments and conduct a large-scale mining study on benchmark configurations. The results show that all three challenges are common: (1) benchmark suite runtimes are often longer than 3 hours; (2) result variability can be extensive, in some cases up to 100\%; and (3) benchmarks often only reliably detect large performance changes of 60\% or more.To address the challenges, we devise targeted solutions as well as adapt well-known techniques from other domains for software microbenchmarks: (1) a solution that dynamically stops benchmark executions based on statistics to reduce runtime while maintaining low result variability; (2) a solution to identify unstable benchmarks that does not require execution, based on statically-computable source code features and machine learning algorithms; (3) traditional test case prioritization (TCP) techniques to execute benchmarks earlier that detect larger performance changes; and (4) specific execution strategies to detect small performance changes reliably even when executed in unreliable cloud environments.We experimentally evaluate the solutions and techniques on real-world benchmarks and find that they effectively deal with the three challenges. (1) Dynamic reconfiguration enables to drastically reduce runtime by between 48.4\% and 86.0\% without changing the results of 78.8\% to 87.6\% of the benchmarks, depending on the project and statistic used. (2) The instability prediction model allows to effectively identify unstable benchmarks when relying on random forest classifiers, having a prediction performance between 0.79 and 0.90 area under the receiver operating characteristic curve (AUC). (3) TCP applied to benchmarks is effective and efficient, with APFD-P values for the best technique ranging from 0.54 to 0.71 and a computational overhead of 11\%. (4) Batch testing, i.e., executing the benchmarks of two versions on the same instances interleaved and repeated as well as repeated across instances, enables to reliably detect performance changes of 10\% or less, even when using unreliable cloud infrastructure as execution environment.Overall, this dissertation shows that real-world software microbenchmarks are considerably affected by all three challenges (1) runtime, (2) result variability, and (3) performance change detection; however, deliberate planning and execution strategies effectively reduce their impact.},
	author = {Laaber, Christoph}
}
