Performance

GC: free-recall review

Crux Free-recall prompts across the GC unit. Answer each in your own words first, then reveal the model answer and compare.

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◷ 14 min

Retrieval beats re-reading. For each prompt, say or write a full answer from memory before you open the model answer — the effort of recall is what makes the material stick.

Goal

Reconstruct the unit’s core mechanisms — live set vs RSS, the generational hypothesis, GOMEMLIMIT, tri-color marking, and the fix-priority ladder — without looking back at the lessons.

Recall before you leave

01
Why does allocation rate drive GC-driven tail latency more than total heap size?
02
State the generational hypothesis and give one counterexample collector.
03
What is the difference between RSS and the live set, and why does it matter for tuning?
04
Explain the tri-color invariant and what the write barrier does to preserve it.
05
What does GOMEMLIMIT do, and why is it the first knob for a containerised Go service?
06
List the GC-pressure fix levers in priority order, highest leverage first.

Recap

If you could reconstruct each answer from memory, you hold the unit’s spine: allocation rate sets frequency, live set sets cost, the generational hypothesis explains most collectors (and Go’s deliberate exception), the tri-color invariant plus write barriers make concurrent marking correct, GOMEMLIMIT defends a container’s bound, and the fix ladder always starts with eliminating allocations — not tuning.

Continue the climb ↑GC: code and trace reading