How would you tune JVM performance for a high-throughput application?

Heap sizing: -Xms/-Xmx (start/max heap), typically same to avoid resizing. GC selection: G1 for balanced, ZGC/Shenandoah for low latency, Parallel for throughput. Young gen ratio: -XX:NewRatio or NewSize. G1 tuning: MaxGCPauseMillis, InitiatingHeapOccupancyPercent. Monitoring: GC logs (-Xlog:gc*), jstat, jconsole, VisualVM. Metaspace: -XX:MaxMetaspaceSize. Code cache: -XX:ReservedCodeCacheSize. Analysis: heap dumps for memory leaks, thread dumps for contention. String deduplication: -XX:+UseStringDeduplication. Profile first (JMH, async-profiler), then tune. Avoid premature optimization.