turbo-tasks-backend: anchor GC roots, gate on Data residency, wire up the app#95977
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This was referenced Jul 20, 2026
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Stats from current PR🔴 1 regression, 1 improvement
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View diffsapp-page-exp..ntime.dev.jsfailed to diffapp-page-exp..time.prod.jsfailed to diffapp-page-tur..ntime.dev.jsfailed to diffapp-page-tur..time.prod.jsfailed to diffapp-page-tur..ntime.dev.jsfailed to diffapp-page-tur..time.prod.jsfailed to diffapp-page.runtime.dev.jsfailed to diffapp-page.runtime.prod.jsfailed to diffapp-route-ex..ntime.dev.jsDiff too large to display app-route-ex..time.prod.jsDiff too large to display app-route-tu..ntime.dev.jsDiff too large to display app-route-tu..time.prod.jsDiff too large to display app-route-tu..ntime.dev.jsDiff too large to display app-route-tu..time.prod.jsDiff too large to display app-route.runtime.dev.jsDiff too large to display app-route.ru..time.prod.jsDiff too large to display pages-api-tu..ntime.dev.jsDiff too large to display pages-api-tu..time.prod.jsDiff too large to display pages-api.runtime.dev.jsDiff too large to display pages-api.ru..time.prod.jsDiff too large to display pages-turbo...ntime.dev.jsDiff too large to display pages-turbo...time.prod.jsDiff too large to display pages.runtime.dev.jsDiff too large to display pages.runtime.prod.jsDiff too large to display server.runtime.prod.jsDiff too large to display use-cache-pr..ntime.dev.jsDiff too large to display use-cache-pr..ntime.dev.jsDiff too large to display use-cache-pr..ntime.dev.jsDiff too large to display use-cache-pr..ntime.dev.jsDiff too large to display 📎 Tarball URLCommit: bfd2a20 |
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… the app Makes GC correct and safe on a real application. - gc_root: a task created with no parent (parent == None) — spawned from outside the tracked graph (a turbo_tasks.run/NAPI entry, run_once, OperationVc::connect outside a task) — is marked a GC root (a persisted meta flag) and never collected. Without this, root operations reached parent_count 0 once their transient creator finished and GC collected them, cascading into their whole subgraph. Expands TaskFlags to u32 for the new flag. - Data-resident gate: gc_maybe_collectible also requires Data restored, so GC never selects a task whose type-bearing Data was evicted (which crashed at snapshot). Stop-gap with a TODO (real fix: restore-Data-in-GC or type-hash-in-Meta). - DetachedVc pins its OperationVc across the NAPI boundary; partial-evict pinned tasks rather than force full residence. - VersionedContentMap: serialization = "skip" + evict = "never" + pin/unpin the OperationVcs it stores, so the ops held in its State are anchored. Tests: gc_does_not_collect_parentless_root_task, the flag-layout tests, and the pinned/ root scenarios.
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What
Makes GC correct and safe on a real application: anchors GC roots, refuses to collect tasks whose data isn't resident, and wires the anchoring into the app.
gc_root: a task created with no parent (parent == None) — spawned from outside the tracked graph (aturbo_tasks.run/NAPI entry,run_once, orOperationVc::connectoutside a task) — is marked a GC root (a persisted meta flag) and is never collected. Without this, root operations reachparent_count == 0once their transient creator finishes and GC collects them, cascading into their whole subgraph. ExpandsTaskFlagsfrom u16 to u32 to make room for the flag.gc_maybe_collectiblealso requires Data restored, so GC never selects a task whose type-bearing Data was evicted (which crashed at snapshot). Interim stop-gap with aTODO— the real fix is restore-Data-in-GC or moving the task-type-hash into Meta.DetachedVcpins itsOperationVcacross the NAPI boundary; pinned tasks are partially evicted rather than forced fully resident.VersionedContentMap:serialization = "skip"+evict = "never"+ pin/unpin of theOperationVcs it stores, so the ops held in itsStateare anchored (they live outside the task graph and would otherwise be collected).Why
The collection pass (PR below) is correct for graph-reachable tasks but over-collects anything held outside the tracked graph — the project container, per-request operations, and ops stashed in long-lived
State. This PR anchors those.Known tradeoff (interim)
gc_rootis a permanent pin, so request-scoped roots (e.g. a fresh source-map/trace operation per navigation) accumulate uncollected within a session. This is the conservative correctness-over-reclamation choice; a real root lifecycle is a follow-up.Verification
Backend GC suites (incl.
gc_does_not_collect_parentless_root_taskand the flag-layout tests), and a dev-app run withTURBO_ENGINE_GCenabled through navigation/HMR cycles — no crashes, dead leaves collected.Stack
Top of the parent_count GC stack; depends on all PRs below it. This is the complete feature.