Under the Hood of a JVM Application - Java Flight Recorder / Java Mission Control
summary
Demonstrates using Java Flight Recorder (JFR) and Java Mission Control to diagnose JVM-level bottlenecks in a git-hash demo that reads ~650,000 files (~20 GB) with virtual threads. Shows how to start and inspect JFR recordings via JVM args, jcmd or the programmatic API (and mentions JFR event streaming), discovers a synchronized lock, a tiny 512‑byte read buffer, and a Files API exception hotspot, and reports incremental fixes that raise throughput from 36k → 54k → 110k → 177k files/s (5.6 GB/s) with measured runtime overhead around 1% (3% with profiling).
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chapters (22)
- 0:00Introduction
- 1:44Observability limits of classic tools
- 2:46Java Flight Recorder and Mission Control
- 4:53Start a JFR recording
- 8:23Demo app overview
- 11:33First run and initial analysis
- 13:01Open JFR file
- 14:04Lock contention analysis
- 15:53Optimize after lock fix
- 16:35Second run and new findings
- 17:17File read operations analysis
- 18:44Optimize buffer size
- 20:30Third run and performance gains
- 21:12Exception analysis
- 22:18Fix JDK performance bug
- 24:23Fourth run with JDK patch
- 25:07Final observations and optimizations
- 26:11Performance gains and best practices
- 27:33When to use JFR and Mission Control
- 32:31Conclusion and recommendations
- 36:43Resources for further reading
- 38:14Q&A
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