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Claude
328aafae77
Commit the spec and scaffold the system it describes:
- SPEC.md: the full v0.1 engineering spec
- crates/: trust-layer Rust workspace, unit-tested
- bench-runner: interleaved ABAB scheduling with discarded warm-ups,
deterministic bootstrap CIs over the ratio of medians,
CI-lower-bound accept rule, env fingerprinting, and a CLI with
compare + A/A self-test modes (A/A verified passing end-to-end)
- diff-test: gate outcome model, sha256 corpus pin verifier that
refuses on mismatch, per-target equivalence policy parser
(byte-identical default, explicit fp-tolerance opt-in)
- ledger: append-only SQLite attempt schema with UPDATE/DELETE
refused by triggers, anti-double-attempt query
- report: cores-saved and dollars/yr ROI math over speedup CIs,
pricing.toml inputs
- playbook/: classes 1-7 with preconditions, procedure, verification
notes, and known failure modes per class
- agent/: Python package skeleton — six-tool contract and prompting
spine, harness IPC deferred to Phase 1
- config/: accept.toml (2% threshold, 30 runs/side), pricing.toml
- targets/, corpora/, results/calibration/: layout and policy docs
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EcKPWQ3MQD4NdEHwar96u2
37 lines
1.6 KiB
Markdown
37 lines
1.6 KiB
Markdown
# Class 2 — Allocator swap
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Link-line only. With class 1, forms the "your 30% was a linker flag"
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tier that is always exhausted before touching source.
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## Preconditions
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- Profile signature: `malloc`/`free`/`operator new` or allocator-internal
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symbols (`_int_malloc`, `tcache_*`, page-fault handling) ≥5% of
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exclusive samples; or high syscall time in `mmap`/`brk`; or
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multithreaded target with allocator lock contention visible.
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## Procedure
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1. Rust: add `mimalloc` (then `jemallocator`) as `#[global_allocator]` —
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two-line diff, still effectively link-level.
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2. C/C++: `LD_PRELOAD` trial first (free experiment, no rebuild), then
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proper linking of the winner.
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3. Bench each candidate allocator separately; do not stack with other
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changes.
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## Verification notes
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- Behavior-preserving by contract, so gates should pass trivially — but
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run them all anyway: allocator swaps change address-space layout and
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can unmask latent UB (use-after-free that "worked" under glibc). A
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sanitizer failure here is a pre-existing target bug: record it,
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route to `needs-human-review`, do not ship.
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- Max RSS is captured per run: an allocator that wins time but doubles
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memory is a trade-off the report must state, not hide.
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## Known failure modes
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- Wins on the bench box's core count that vanish (or invert) at the
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fleet's concurrency level.
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- `LD_PRELOAD` trial passing but static-link integration subtly failing
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(symbol interposition differences) — re-run full gates on the final
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link, not the trial.
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- Fragmentation pathologies on long-running services that a short bench
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window never sees; service-mode targets need soak evidence (Phase 4).
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