Performance Benchmarking & Tuning Flashcards
7 cards from real CSI practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Performance Benchmarking & Tuning flashcards as text
Which metric best indicates whether a system is CPU-bound versus I/O-bound during a benchmark run?
Answer: CPU utilization vs. I/O wait percentage
Comparing CPU utilization to I/O wait time reveals whether the bottleneck is processing power or storage throughput.
A load test shows response times increase linearly with user count up to 100 users, then spike sharply. What does this pattern most likely indicate?
Answer: A resource saturation point has been reached
A sudden spike after linear scaling indicates a saturation point where a bottlenecked resource can no longer queue additional requests efficiently.
What is the primary purpose of a 'warm-up' phase at the start of a performance benchmark?
Answer: Allow JIT compilation and caches to reach steady state
A warm-up phase lets the JVM JIT-compile hot paths and populate caches so benchmark measurements reflect steady-state performance rather than cold-start overhead.
In capacity planning, the term 'headroom' refers to:
Answer: The unused resource capacity reserved for traffic spikes
Headroom is the intentional buffer of unused capacity kept available so unexpected load spikes do not immediately saturate the system.
Which profiling technique adds the least overhead and is most suitable for production environments?
Answer: Sampling profiler
Sampling profilers interrupt execution at intervals to record the call stack, adding minimal overhead compared to instrumenting every method call.
When tuning a database for read-heavy workloads, which adjustment typically yields the greatest performance gain?
Answer: Increasing the buffer pool or cache size
Enlarging the buffer pool keeps frequently accessed data in memory, dramatically reducing disk I/O for read-heavy workloads.
A benchmark reports 99th-percentile latency of 2,000 ms while median latency is 50 ms. What does this gap most likely indicate?
Answer: Occasional long garbage collection pauses or lock contention
A large gap between median and tail latency typically points to intermittent events like GC pauses, lock contention, or resource exhaustion affecting a small fraction of requests.