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Oh no, the production environment is experiencing frequent Full GC, what should I do?
In almost every Java backend interview, the classic question appears: “Your online service is experiencing frequent Full GCs, how do you troubleshoot and resolve it?”
Today, let’s systematically walk through the entire process from discovery → location → root cause analysis → optimization, using real production cases, hoping to give you a complete mental model and practical toolkit.
1. What exactly is Full GC and why is it deadly?
When the old generation is unable to allocate space for new objects (including objects promoted from the young generation), the JVM triggers a Full GC (Major GC). During this period, Stop-The-World occurs — all application threads are paused.
Real production hazards (actual measured data):
In high-concurrency systems, even a 2-second pause can cause cascading failures.
