Introduces journald RateLimitBurst/Interval, why throttling noisy logs matters, and how to scope limits per unit.

Covers chapter 4 topics: static vs dynamic instrumentation, profiling vs tracing, and expected sampling overheads.

Summarizes chapter 3 Q&A on OS terminology, process/thread differences, memory management, and kernel duties.

Answers Systems Performance chapter 2 exercises, clarifying metrics like IOPS, utilization, and troubleshooting methodologies.

Explains how systemd drop-in units override service sections (GitLab Runner example) and how to inspect active overrides with systemctl.