pocketjs-psp-benchmark

name	pocketjs-psp-benchmark
description	Benchmark PocketJS demos on PSP or PPSSPP, including per-frame timing, renderer phase costs, bundle and pak sizes, arena high-water memory, and minimum passing arena scans. Use when asked to profile PSP performance, compare demo frame budgets, measure memory headroom, find the minimum safe heap for demos, or preserve benchmark evidence in dist/bench.

PocketJS PSP Benchmark

Overview

Use this skill to produce repeatable PocketJS PSP benchmark evidence instead of ad hoc emulator runs. Prefer scripts/bench-ppsspp.ts for local PPSSPP measurements; use scripts/hw.ts only when the user explicitly asks for real PSP hardware proof.

Standard Workflow

1. Confirm the worktree is on the intended branch and inspect local changes with git status --short --branch.
2. Confirm host dependencies before long runs:

test -x "${PPSSPP_HEADLESS:-$HOME/ppsspp-src/build/PPSSPPHeadless}"
test -n "$PSP_SDK" && test -f "$PSP_SDK/psp/lib/libc.a"

3. Run a focused benchmark while iterating:

PSP_SDK=/path/to/mipsel-sony-psp BENCH_PPSSPP_TIMEOUT=60 \
  bun scripts/bench-ppsspp.ts --apps=stats --samples=3

4. Run the full suite and memory scan for release-quality evidence:

PSP_SDK=/path/to/mipsel-sony-psp BENCH_PPSSPP_TIMEOUT=60 \
  bun scripts/bench-ppsspp.ts --apps=all --samples=3 --memory-scan

5. Preserve the generated evidence paths from dist/bench/ in the final answer, PR body, or handoff. The .json file is authoritative; the .md file is for human review; .raw.jsonl keeps per-sample and memory-probe records.

Memory Scans

Use --memory-scan when the user asks for minimum memory, heap headroom, safe arena sizing, or whether all demos fit. The runner first measures uncapped arena high-water, then probes capped POCKETJS_ARENA_BYTES values in --memory-step-kib increments. The reported suite requirement is the maximum safe arena across selected apps.

Default safety policy is:

safe_arena = min_passing_arena + max(512 KiB, 20% of min_passing_arena)

Override it only when the user specifies a different margin:

bun scripts/bench-ppsspp.ts --apps=all --samples=3 --memory-scan \
  --memory-step-kib=128 --memory-safety-kib=1024 --memory-safety-percent=25

Interpreting Results

Use avg_work_us against the 60 Hz budget of about 16667us. max_work_us can spike on transitions, but a sustained average over budget is a performance finding.

Use arena_bump_bytes as the allocator high-water for the run. Use min_pass_arena_bytes as the probed lower bound at the configured step size, and safe_arena_bytes as the answer when the user asks for a minimum with safety margin.

Read references/metrics.md when you need field definitions, caveats, or exact wording for a benchmark report.

Reporting

Always include:

• command run
• report path
• selected apps and sample count
• PPSSPP revision and git revision from the report
• suite safe arena when --memory-scan was used
• any app whose avg_work_us exceeds the frame budget

Do not claim real hardware proof from a PPSSPP run. State PPSSPP evidence as emulator evidence unless scripts/hw.ts or a real PSP run was actually used.