Generate Flamegraph Using perf record and Flamegraph.pl

Stack Samples as a Heat Map

Flame graphs turn thousands of perf record stack samples into one SVG where width equals sample count. Brendan Gregg invented them to answer which functions dominate CPU time across whole call chains, not just flat self time. Kernel developers, database teams, and game studios use the same workflow when a service is hot but the culprit function is buried five frames deep.

From Samples to SVG

Record at high frequency, collapse stacks, feed them to flamegraph.pl. The y-axis is stack depth; the x-axis is proportion of samples. Wide plateaus are where you optimize first.

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• Use -g so call chains appear, not just leaf symbols
• Disable ASLR only when you need stable addresses for diffing two runs
• Compare two flame graphs side by side after a change to confirm the hotspot moved
• Idle time does not appear; profile under realistic load

Working Through the Exercise

Keep the relevant documentation open while you implement. When your output disagrees with the reference, trace one failing case by hand before changing random lines.

• Trace first: walk one failing input step by step
• Read the manual: skim the official doc for the mechanism named in this task
• Compare baselines: save measurements from the prior step so speedups are honest

Why for this exercise

You will write a program with deliberate hotspots and generate a flame graph from perf record output. This exercise requires you to identify the widest frame and tie it back to a specific loop in your source.