I’m a PhD researcher in the Programming Languages & Systems group at the University of Kent, supervised by Dr Stefan Marr.
My research focuses on a long-standing challenge: why Java profilers are so inaccurate, and why they disagree on what’s “hot.”
Sampling profilers can mislead developers, while traditional instrumentation can distort performance by orders of magnitude.

My work includes empirical studies of both sampling-based and instrumentation-based profilers. I have also developed a late compiler-stage instrumentation tool, BuboC, which avoids interfering with major compiler decisions, reducing overhead and minimising the observer effect.

I’m also designing techniques to measure profiler accuracy itself, introducing controlled slowdowns that reveal whether profilers can detect the true performance behaviour.

Finally, I have developed a loop-centred instrumentation profiler inside the Graal compiler. This tool, BuboL, provides more accurate measurements of CPU time spent inside loops when compared with CPU sampling profilers.

🎯 Goal: Build profiling techniques that are accurate, practical, and measurable against ground truth.

• Burchell, H., & Marr, S. (2025).
  Divining Profiler Accuracy: An Approach to Approximate Profiler Accuracy Through Machine Code-Level Slowdown.
  Proceedings of the ACM on Programming Languages (OOPSLA ’25).

• Burchell, H., & Marr, S. (2025).
  Evaluating Candidate Instructions for Reliable Program Slowdown at the Compiler Level: Towards Supporting Fine-Grained Slowdown for Advanced Developer Tooling.
  17th ACM SIGPLAN International Workshop on Virtual Machines and Intermediate Languages (VMIL ’25), Singapore.

• Burchell, H., Larose, O., & Marr, S. (2024).
  Towards Realistic Results for Instrumentation-Based Profilers for JIT-Compiled Systems.
  21st ACM SIGPLAN International Conference on Managed Programming Languages and Runtimes (MPLR ’24), Vienna.

➡️ View all publications in KAR

If you’re interested in:

• Profilers and instrumentation
• CPU sampling and performance analysis
• Compiler-level slowdown

Feel free to get in touch!

📫 Email: humphreyburchell@gmail.com

_{© 2026 Humphrey Burchell}