Flamegraphs

Flamegraphs

Purpose

Guide agents through the pipeline from profiler data to SVG flamegraph, and teach interpretation of flamegraphs to drive concrete optimisation decisions.

Triggers

• "How do I generate a flamegraph from perf data?"
• "How do I read a flamegraph?"
• "The flamegraph shows a wide frame — what does that mean?"
• "How do I generate a flamegraph from Callgrind?"
• "I want to compare two flamegraphs (before/after)"

Workflow

1. Install FlameGraph tools

git clone https://github.com/brendangregg/FlameGraph
# No install needed; scripts are in the repo
export PATH=$PATH:/path/to/FlameGraph

2. perf → flamegraph (most common path)

# Step 1: record
perf record -F 999 -g -o perf.data ./prog

# Step 2: generate script output
perf script -i perf.data > out.perf

# Step 3: collapse stacks
stackcollapse-perf.pl out.perf > out.folded

# Step 4: generate SVG
flamegraph.pl out.folded > flamegraph.svg

# Step 5: view
xdg-open flamegraph.svg     # Linux
open flamegraph.svg          # macOS

One-liner:

perf record -F 999 -g ./prog && perf script | stackcollapse-perf.pl | flamegraph.pl > fg.svg