NOTE
Flame Graphs
Visualizing aggregated stack samples to locate CPU or off-CPU hotspots.
This is a historical learning note and may contain outdated or incomplete understanding.
A flame graph aggregates sampled stack traces. The x-axis width represents the number of samples attributed to a stack path; it is not a chronological timeline. The y-axis represents stack depth.
CPU flame graphs reveal where on-CPU samples accumulate. Off-CPU/blocking profiles answer a different question: where execution waits for locks, I/O, timers, or scheduling.
Good profiling requires representative load, enough samples, correct symbols, and awareness of sampling bias.