next.js

9970e23b - [turbo-tasks] Shrink RawVc to 8 bytes and CellId to 4 bytes (#94792)

[turbo-tasks] Shrink RawVc to 8 bytes and CellId to 4 bytes (#94792) ### What? Shrink `RawVc` (16 → **8 bytes**) and `CellId` (6 → **4 bytes**), by hand-packing them into `NonZero` integers. ### Why? `RawVc` is the type-erased representation behind every `Vc` / `ResolvedVc` / `OperationVc`, and `CellId` keys every task cell. They live in huge numbers in the cache keys and task storage to track cells. Cutting `RawVc` in half and `CellId` by a third removes hundreds of megabytes of peak RSS on a real, large app. ### How? | Type | Before | After | Representation | |-----------|----------|----------|----------------| | `CellId` | 6 bytes | **4 bytes** | `NonZeroU32`: `ValueTypeId` in the top 10 bits, cell index in the low 22 bits | | `RawVc` | 16 bytes | **8 bytes** | `NonZeroU64`; bit 31 flags `LocalOutput`, and the two task variants are split by whether the high-32-bit `CellId` field is zero | Supporting changes: - **`TaskId` constrained to 31 bits** - **`ValueTypeId` capped at 1023** (10 bits) and **cell index capped at ~4.19M** (22 bits), enforced at the registry and cell-allocation sites. Together those restrictions enable us to preserve a bit to use as a discreminent in RawVc and pack `CellId` into a u32 ### Perf Building vercel-site, 5 runs each. `maxRSS` and `user CPU` are means; `wall` is the median | Condition | Branch | maxRSS | wall (s) | user CPU (s) | |---|---|---|---|---| | No persistence | canary | 13.64 GiB | 41.56 | 305.64 | | No persistence | **this PR** | **13.04 GiB** | 40.72 | 299.52 | | | | **−4.4%** | −2.0% | −2.0% | | Persistence | canary | 17.19 GiB | 55.20 | 466.54 | | Persistence | **this PR** | **16.30 GiB** | 55.12 | 462.33 | | | | **−5.2%** | −0.1% | −0.9% | <!-- NEXT_JS_LLM_PR -->