Profile Rust Code

Measure Before You "Optimize"

Rust is fast by default, but hot paths still need data. Linux perf samples CPU stacks; cargo flamegraph wraps it into an SVG where width means time. Cloudflare and Discord publish wins found exactly this way.

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• Always profile --release; debug builds distort inlining and arithmetic
• Wide plateaus in the flamegraph are functions worth attention
• criterion microbenches guard against optimizing noise

Reading the Output

perf report sorts symbols by sample count. If 40% lands in memcpy, fix allocation patterns before tweaking algorithms. If a mutex shows up wide, fix contention.

For this exercise, you will profile a small CPU-heavy program and name the top frames. This task asks you to propose one change backed by numbers, because profiling culture is what separates Rust marketing from Rust performance in production.

Keep the relevant man page, ABI doc, or Rust reference chapter open while you work. When your output disagrees with the reference implementation on the same machine, the mismatch is usually an alignment rule, an off-by-one terminator, or a register slot you misread in GDB. Skim the official documentation for the tool or ABI named in the exercise; the prose changes, but register roles, syscall numbers, and ownership rules stay stable across releases.