68bac2a70e
### What? In `turbo-tasks-fs`, the `WriteEffect` and `WriteLinkEffect` structs now store a precomputed `u128` xxh3 content hash instead of returning the full `ReadRef<PersistedFileContent>` / `ReadRef<LinkContent>` from their `Effect::value()` implementations. The associated type `Effect::Value` is changed from `ReadRef<PersistedFileContent>` / `ReadRef<LinkContent>` to `u128` for both effect types. `LinkContent` gains a `DeterministicHash` derive to support hashing via `hash_xxh3_hash128`. ### Why? `EffectStateStorage` stores the last-applied value for each effect key in `last_applied: Mutex<Option<Box<dyn Any + Send + Sync>>>` to enable a double-checked deduplication fast path (skip re-writing a file if content hasn't changed). In long-running sessions this map grows continuously and holds onto a lot of memory because it stores full file content (`ReadRef<PersistedFileContent>`) or full link content (`ReadRef<LinkContent>`) for every file ever written. Storing a `u128` hash (16 bytes) instead of the full content significantly reduces memory usage while preserving the deduplication semantics (hash equality implies content equality with negligible collision probability). ### How? - Added `content_hash: u128` field to `WriteEffect` and `WriteLinkEffect`, computed at construction time using `hash_xxh3_hash128` (xxh3 128-bit non-cryptographic hash, already used elsewhere in turbopack for content addressing). - Changed `Effect::Value = u128` for both effect types; `value()` returns `&self.content_hash`. - The `EffectStateStorage` now stores `Box<u128>` (24 bytes on the heap) per entry instead of `Box<ReadRef<...>>` which held a reference-counted pointer into potentially large file content. - No changes to `EffectStateStorage`, `Effects::apply()`, or `DynEffect` vtable — the existing `Any`/`DynPartialEq` machinery works transparently with `u128`. <!-- NEXT_JS_LLM_PR --> Co-authored-by: Tobias Koppers <[email protected]> Co-authored-by: Claude <[email protected]>
Next.js
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