Visualizing with Speedscope

Using Speedscope for interactive, multi-dimensional profile exploration.

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Why Speedscope?

While static SVG flamegraphs are excellent for quick inspections, Speedscope provides an interactive web-based interface designed specifically for performance analysis. It supports:

• Chronological view (Time Order): Visualizes exactly what happened in execution order.
• Aggregated view (Left Heavy): Merges common call paths to reveal bottlenecks.
• Sandwich view: Shows all callers and callees of a specific function.

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Exporting Folded Stacks

soroban-cost-profiler can export folded stack format directly:

soroban-cost-profiler \
  --wasm target/wasm32-unknown-unknown/profiling/my_contract.wasm \
  --fn process_deposit \
  --format speedscope \
  --output profile.folded

The resulting file contains lines formatted as:

root;init_ledger;verify_caller 14500
root;process_deposit;calculate_interest 280000
root;process_deposit;update_balances;storage_set 1920000

Where the final integer represents the number of metered CPU instructions consumed on that path.

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Loading into Speedscope

1. Open https://www.speedscope.app in your browser.
2. Drag and drop profile.folded onto the window.
3. The file is parsed completely locally in your browser—no contract bytecode or execution data leaves your machine.

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The Three Speedscope Views

1. Time Order View

In the Time Order view, the horizontal axis represents the progression of execution time (instruction order).

• Use this to see the execution lifecycle: initialization $\to$ authorization checks $\to$ core math $\to$ state updates $\to$ event emission.
• Quickly identify if a slow operation occurred early or late in the transaction.

2. Left Heavy View

In the Left Heavy view, all identical call stacks are grouped and sorted with the heaviest consumers on the left.

• Instantly answers: "Which single function consumed the largest slice of the transaction fee?"

3. Sandwich View

Click on any function in the list to open the Sandwich view:

• Top panel: Shows all functions that called this function (and what percentage of cost came from each caller).
• Middle panel: The selected function itself.
• Bottom panel: All child functions called by this function.