How do I check for V8 deoptimization in Node.js?
Run with the --trace-deopt flag. This shows deoptimization events, telling you if your code is hitting the optimized path or falling back to interpreted bytecode. It reveals why a function is slower than expected.
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More FAQs in How to Debug V8 and Node.js Performance Issues
Use the CPU profiler to find the bottleneck, --trace-deopt to check for deoptimization, heap snapshots for memory issues, event loop monitoring for blocking code, clinic.js for blocking detection, and --trace-warnings for performance warnings.
Take heap snapshots with the Node.js inspector. Compare snapshots over time to find growing objects, which point to memory leaks or excessive allocation. This is the standard way to debug memory issues in production.
Blocking the event loop with synchronous code. This stops all requests while the blocking code runs. Use tools like clinic.js and event loop lag monitoring to detect blocking operations and long-running synchronous code.
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