JVM / Kotlin Performance Fix Playbook

Prerequisite: Use /jfr-profiling first to identify what's hot. This skill answers "now that I know the hotspot, what do I change?"

Rule: The smallest targeted change that removes the bottleneck. Don't touch cold paths.

To collect the profiling data that identifies these hotspots, apply the jfr-profiling skill first.

Allocation / GC Pressure

What you see in the profile

• GarbageCollector / G1YoungCollect / ZMarkStart consuming > 5–10% of samples
• Allocation flame graph shows a specific call site allocating heavily
• jfrconv --alloc reveals repeated construction of the same type