104 lines
4.5 KiB
Markdown
104 lines
4.5 KiB
Markdown
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# wasm-opt allocator/core benchmark
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Fast, local feedback loop for the CI perf issue: the host-side `wasm-opt`/asyncify
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pass (`scripts/common/apply-asyncify.sh`) is slow on the glibc Linux CI runner
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because glibc `malloc` collapses into per-arena lock (`futex`) contention under
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many threads. We preload **jemalloc** to fix it. This harness measures the effect
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locally instead of paying for a full ~160-min Hetzner CI run per experiment.
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**Key idea:** `wasm-opt`/asyncify is a standalone pass over an *already-compiled*
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`.wasm` (`docker/build.sh:194`). So we build the eeschema `.wasm` **once** on the
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Mac, copy it into a Linux VM, and replay only the optimizer across a matrix of
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`{glibc, jemalloc} × core counts`. No KiCad compile happens in the VM.
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## Caveats (read before trusting numbers)
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- **This Mac is 10 cores / 32 GB.** The local core sweep tops out at ~10 threads.
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The CI runner is 32 vCPU, so the *full* 32-thread contention is **not**
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reproducible here — the local run shows the **direction** (jemalloc vs glibc,
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and how wall-clock scales with cores), not CI's absolute worst case. The final
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32-thread pick must still be confirmed on the real runner.
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- **aarch64 ≠ CI's x86_64.** The VM is aarch64 (HVF, near-native speed). The
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glibc arena-lock pathology is arch-independent, so the **ratios** transfer;
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**absolute seconds do not** match the x86_64 AMD runner.
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- asyncify peaks ~10–15 GB RAM → the VM gets 20 GB; close other heavy apps.
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## 1. Build the fixture (once, on the Mac)
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```bash
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mkdir -p bench
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./docker/build.sh eeschema --build-deps # long: full cold build
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# Pull the Docker-side raw (pre-finalize) wasm while the builder container is up:
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docker compose -f docker/docker-compose.yml cp \
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kicad-wasm-builder:/workspace/build-wasm/kicad-eeschema/eeschema/eeschema.wasm \
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bench/eeschema.raw.wasm
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# Finalize it to match what asyncify actually consumes in the pipeline:
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./scripts/common/apply-finalize.sh bench/eeschema.raw.wasm bench/eeschema.finalized.wasm
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```
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Fallback if `compose cp` fails:
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`docker compose -f docker/docker-compose.yml exec kicad-wasm-builder cat <path> > bench/eeschema.raw.wasm`
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## 2. Provision and boot the VM (Mac)
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```bash
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brew install qemu # one-time
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./scripts/bench/setup-vm.sh prepare
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./scripts/bench/setup-vm.sh run # serial console; quit with Ctrl-a x
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```
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Wait ~1–2 min for cloud-init (installs git/curl/time/libjemalloc2/strace).
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## 3. Load repo + fixture into the VM
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```bash
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# from the Mac, in another terminal:
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scp -P 2222 -o StrictHostKeyChecking=no bench/eeschema.finalized.wasm bench@localhost:~/
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./scripts/bench/setup-vm.sh ssh
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# inside the VM:
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git clone <this-repo-url> repo && cd repo
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git checkout istvanmatejcsok/feat/ci-hetzner-allcores
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mkdir -p bench && mv ~/eeschema.finalized.wasm bench/
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# get-wasm-opt.sh auto-downloads Binaryen v121 aarch64-linux on first use
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```
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## 4. Run the benchmark (in the VM)
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```bash
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STRACE=1 ./scripts/bench/wasm-opt-bench.sh
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```
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Sweeps `CORES="1 4 8 10"` × `{glibc, jemalloc}`, writing `bench/results.csv`
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(wall-clock + peak RSS per cell) and per-cell logs under `bench/results/`. With
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`STRACE=1` it also records `futex` syscall share per allocator (expect ~99% on
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glibc, far lower with jemalloc). Override the sweep with e.g. `CORES="8 10"`.
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## Interpreting
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- jemalloc rows should show **lower wall-clock** than glibc, widening as cores rise.
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- glibc wall-clock that *stops improving* (or worsens) with more cores = the
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arena-lock storm; jemalloc should keep scaling.
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- These ratios justify the `LD_PRELOAD` fix; use them (plus one real-runner
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confirmation) to choose CI's `BINARYEN_CORES`.
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Artifacts (`bench/*.wasm`, `bench/results*`, `scripts/bench/vm/`) are gitignored.
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## 5. Full Docker build in the VM (CI dry-run) — vm-build.sh
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Verifies CI orchestration changes (docker/build.sh, compose limits, pipelining)
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on Linux+Docker without burning a Hetzner slot. The guest is aarch64/HVF:
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a *functional* CI proxy, not an x86 performance proxy.
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```bash
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# one-time: bigger disk + Docker-enabled cloud-init, then boot
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VM_DISK=80G ./scripts/bench/setup-vm.sh prepare
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./scripts/bench/setup-vm.sh run # leave running in its own terminal
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# from the Mac: cold calculator build inside the guest (deps + docker image)
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./scripts/bench/vm-build.sh # = calculator --build-deps
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# pipeline smoke test (deps already in the guest volume from the previous run)
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KICAD_PIPELINE=1 ./scripts/bench/vm-build.sh calculator,pl_editor
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```
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Prints the guest build wall time at the end; build logs stream through ssh.
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