UWSpace

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Recent Submissions

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    Improving Reliability for Networked Systems and Software Execution
    (University of Waterloo, 2026-05-27) Gu, Haoyu
    Reliability is a fundamental requirement for modern software systems and services. As these systems grow larger and serve more users, even minor failures or outages can escalate into critical incidents. Reliability is a broad concept that covers the reliability design of many systems. When narrowed down, three areas still lack good solutions: connection failures in layer 4–7 network functions, software bug triage and diagnosis, and reliably reproducible software executions. This thesis introduces HA/TCP, AutoPecker, and PerfCheck to address each of these problems in turn. HA/TCP improves the reliability of networked systems. HA/TCP is the first framework to support the migration and failover of TCP-based layer 7 network functions (NFs) for reliability and multi-node scalability. HA/TCP does not modify the TCP protocol allowing existing projects to take advantage of HA/TCP without client changes. HA/TCP actively replicates traffic from primary node to all replica nodes to keep the state in sync. In the case of a node failure, HA/TCP enables replica NFs to take over connections in microseconds. Moreover, HA/TCP is completely transparent to the client, such that connection migration/failover is not visible to the client. AutoPecker provides a solution for automatic software bug triage and diagnosis. AutoPecker achieves the best of both worlds by combining a low overhead record/replay system with customized sanitizers and other instrumentation that can be enabled on replay. On a program crash, or by a manual invocation by the user, AutoPecker captures a trace of the program execution and tests it against a suite of sanitizers and programmer assertions. AutoPecker can run on the user’s or developer’s machine to automatically triage the bug and provide a detailed analysis. PerfCheck provides a comprehensive solution for improving the reliability and reproducibility of software execution. PerfCheck collects configurations and specifications of the host system, allowing developers or researchers to share their project together with a PerfCheck report as a configuration baseline. When other researchers attempt to reproduce the execution results, PerfCheck allows them to inspect and identify differences in their local environment configurations, ensuring reliable reproduction.
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    Redesigning Datacenter Systems to Leverage Hardware-Acceleration
    (University of Waterloo, 2026-05-27) Udayashankar, Sreeharsha
    The exponential growth of digital data generation imposes severe performance and efficiency demands on modern datacenter infrastructure, creating unique interrelated challenges. Datacenter infrastructure must offer high data storage capacities, achieve high throughput, and support modern workloads that require low-latency data processing. While hardware accelerators, such as CPUs supporting SIMD vector instruction sets and network switches supporting P4-based programmability, have the potential to help achieve these requirements, their adoption in large-scale systems is hindered by restrictive programming models and resource constraints. This thesis addresses these challenges by redesigning deduplicated storage systems and cluster schedulers to leverage hardware acceleration effectively. It enables high-throughput data reduction in deduplicated storage systems (Chapter 3, Chapter 4, and Chapter 5) by using two approaches: redesigning them to use the SIMD capabilities of modern CPUs and by reducing the computation needed to achieve data reduction. It enables low-latency data processing by leveraging in-network acceleration for cluster scheduling (Chapter 6). The thesis first presents VectorCDC (Chapter 3), a method for accelerating data deduplication by restructuring hashless content-defined chunking (CDC) algorithms to exploit vector instructions. By identifying and optimizing the common processing patterns they use, Extreme Byte Searches and Range Scans, VectorCDC significantly improves their chunking throughputs. VRAM, the fastest VectorCDC-accelerated algorithm achieves throughput improvements of 8.35×–26.2× over existing vector-accelerated techniques and up to 207.2× over unaccelerated baselines. Importantly, VectorCDC maintains its throughput advantages across x86, ARM, and IBM CPU architectures. While generally competitive with their hash-based counterparts, these hashless CDC algorithms achieve lower deduplication efficiency on datasets with specific pathological patterns. To address this, this thesis presents WideCDC (Chapter 4). WideCDC improves the deduplication efficiency of hashless CDC algorithms by basing chunk boundary decisions on wide regions of multiple bytes, instead of singular byte values. To achieve high throughput, WideCDC uses vector-compatible Accumulated Extreme Byte Searches and Gated Range Scans. WideCDC improves deduplication efficiency on pathological datasets by 2.95× and further improves throughput by 2.04× over VectorCDC. Additionally, to address the throughput degradation of CDC algorithms at the large chunk sizes favored by production systems, this thesis presents SeqCDC (Chapter 5). SeqCDC is a novel chunking algorithm that uses a novel lightweight boundary detection mechanism, content-defined data skipping, and a vector instruction-focused design. SeqCDC improves chunking throughput by 10× over unaccelerated algorithms and 25–30% over the fastest vector-accelerated alternatives, while minimally affecting deduplication efficiency. Finally, this thesis proposes Draconis (Chapter 6), a network-accelerated scheduler built using P4 programmable switches, designed to support microsecond-scale workloads. Draconis forgoes the inefficient design adopted by prior switch-based schedulers by implementing a switch-compatible task queue with delayed pointer correction, eliminating the latency penalties caused by node-level blocking. Evaluation results demonstrate that Draconis reduces the 99th percentile scheduling delay by 3×–200× over state-of-the-art network-accelerated solutions, and increases scheduling throughput by 52×–116× over state-of-the-art server-based solutions.
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    Where the Whip-poor-will will: Third and fourth order habitat selection of a migratory aerial insectivore
    (University of Waterloo, 2026-05-27) Pepe, Victoria Anne
    Habitat selection is a hierarchical process operating across multiple spatial scales, with important consequences for survival and reproduction. The Eastern Whip-poor-will (Antrostomus vociferus) is a declining aerial insectivore that relies heavily on crypsis, making habitat use difficult to define because of low detectability and inconspicuous behaviour. As a result, fine-scale habitat selection in this species remains poorly understood. I defined third-order habitat selection of breeding Eastern Whip-poor-will by manually tracking radio-tagged birds across the landscape in Norfolk County, Ontario. Specifically, I characterized (i) whip-poor-will breeding home and core range size, (ii) percent overlap of breeding pairs and neighbouring males, and (iii) defined habitat composition within home ranges to compare with available habitat. Whip-poor-will home and core range size did not differ between sexes, with breeding pairs showing extensive overlap, possibly a result of bi-parental care of the chicks. Though female sample size was small, limiting my ability to robustly assess trends, my study contributes to a limited body of research representing females. Male whip-poor-will exhibited substantial home range overlap with neighbouring males, but little to no overlap at the core range, with density estimates that suggest the population may still be growing instead of steady state. Whip-poor-will home and core ranges were associated with higher proportions of restored open habitat than expected, based on availability. To examine the most refined scale of habitat selection (fourth order) in whip-poor-will, I conducted vegetation surveys to characterize microhabitat of nest sites. Vegetation characteristics at nests were compared with random available sites, and data was collected at three spatial scales: 10 m scale (nest plot plus two random 10 m plots, 30 m from the nest), 1 m random scale (1 m nest plot plus 1 m plot in two random 10 m plots), and 1 m nest scale (1 m nest plot and random 1 m plot 2.5 m away from the nest). Whip-poor-will selected for higher canopy cover at the 10 m scale, and more leaf litter and less grassy substrate at the 1 m random scale, with no selection preferences for the 1 m nest scale. This pattern of preference suggests that whip-poor-will may initially target areas with high canopy cover, then select nest sites based on suitable leaf litter of an area within approximately 2.5 m. Deciduous leaf litter allows for camouflage during incubation and may provide thermal buffering. Leaf litter was mainly comprised of oak leaves, a species that retains senesced leaves into the late winter and early spring (marcescence). Oak leaves also contain high lignin content, which increases rigidity and slows decomposition rates. In combination, marcescence and high lignin result in deciduous leaf litter that persists for longer on the landscape and remains present upon whip-poor-will return to breeding grounds. By characterizing habitat selection across multiple scales, these findings provide ecological insight for understanding how whip-poor-will use restored habitats. As wildlife populations decline, research that informs effective conservation strategies and guides habitat restoration is increasingly important.
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    Operator Representations and Twisted Traces of Cohomological and K-Theoretic Coulomb Branches
    (University of Waterloo, 2026-05-27) Zhang, Keke
    This thesis establishes a rigorous mathematical framework for twisted traces on quantized Coulomb branches in 3D \(\mathcal{N}=4\) supersymmetric gauge theories. By developing an explicit operator representation of the Coulomb branch algebra \(\mathcal{A}_{\hbar}(G, \bN)\) for conical theories, generalized shift operators are constructed to act on a specifically calibrated function space. For non-abelian groups, localization to torus fixed points enables the formulation of monopole operators as symmetrized sums of abelian shift operators. We derive explicit integral formulas for twisted traces, providing a concrete realization of correlation functions previously assumed in the physics literature. These constructions are also extended to K-theoretic Coulomb branches via representations by $q$-difference operators, offering analytical tools to investigate the quantum Hikita conjecture.
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    Techno-Economic Analysis of Bio-Methanol to Sustainable Aviation Fuel Process
    (University of Waterloo, 2026-05-26) Erdmann, Oliver
    There are many sustainable aviation fuel production methods that are currently in use today, like the ethanol alcohol-to-jet process and Fischer-Tropsch. Demands from international aviation bodies and organizations are calling for more development and sources for producing sustainable aviation fuels, and the methanol-to-jet process is a pathway of interest. Currently, there exists no techno-economic work on such a plant model and insights on its profitability, break even costs, and most expensive contributing factors of running a methanol-to-jet plant are unknown. Extensive research and development work on a techno-economic tool from the German Aerospace Center called PyTEEA granted the option of doing economic calculations on an ASPEN plus simulation of the methanol-to-jet plant. The results found that both the cost of bio-methanol fuel or the production of bio-methanol to be the leading expense in running such a plant, with up to 75.95% of the break even cost of 3.26 EUR/kg being attributed to bio-methanol fuel costs alone. Although the methanol-to-jet pathway shows technical promise, it is currently less cost-competitive than other sustainable aviation fuel routes, such as ethanol-to-jet, largely due to the limited availability and high price of bio-methanol. As production capacity and market supply of bio-methanol expand, the methanol-to-jet pathway may become a more viable option for large-scale sustainable aviation fuel deployment.