Merge train 184s: #10217

[proggeramlug]

Merge train 184s: lands #10217 (reclaim dead blocks without visiting them in the synchronous full sweep; Part 1 of #10182) at 0e782c659a, plus the workspace version bump to 0.5.1562. (The "s" suffix keeps clear of the other merge lane's train numbers.)

The three PR commits were cherry-picked onto 6000a00dfe without conflicts.

Validation (macOS arm64)

Validation ran on the same PR over bb9aa5a641. Main has since gained only #10225 (regex files), which #10217 does not touch.

• scripts/run_lint_gates.sh: 80 of 83 pass. The 3 failures are the same steps as main: public benchmark evidence freshness, API docs drift, and -D warnings stopping on main's global_this_webassembly.rs dead code.
• raw_handle_debt.py (both invocations), gc_runtime_root_holders.py, shape_descriptor_census.py, gc_store_site_inventory.py, fmt, file size: pass. check_thread_locals.py: only main's regex/perex_owner.rs.
• cargo test --release -p perry-runtime: 3786 passed / 1 failed. This run includes the test-build safety net that re-walks every skipped block. The failure is gc::tests::heap_generation::a_free_or_move_outside_every_scope_is_caught_in_debug_builds, already on main from perf(regex): resume JS-level searches on non-ASCII strings from the previous call's position #10205. --lib block_skip: 11 / 0.
• Full gap suite (779 tests): 766 pass. Gated failures are main's known set (2899_2779_2777_static_helpers, disposablestack_2875, iterator_prototype_next_patch, gc_http2_pending_event_callback_rooting) plus 9592_child_timeout_threads, where the Node oracle fails on this host. Two further entries were timing flakes on a loaded host: 9574_unlink_waits_for_parked_write passes 3/3 on this build and also fails intermittently with a 9b911855f8 compiler, and 9676_stdin_unref_ref_keeps_reader hit the 10 s harness timeout once, then passed 3/3 on this build and 2/2 with the old compiler.
• The skip's subject is live. A parse-and-drop probe (40k-record documents parsed eight times with three retained, maps, explicit gc()) under PERRY_GC_DIAG=1 reports block_skip_reclaimed_blocks up to 3 and a block of 23,834 objects reclaimed without visiting it. Its output matches Node except the final WeakRef.deref() of an unreferenced object, which Perry clears after gc() while Node still holds it. JS permits either, and it is identical across the plain, diagnostic and GC-stress runs. Under PERRY_GC_SCHEDULE_SEED 7 and 184 at rate 0.2, with forced evacuation, verification and from-space protection (917 and 935 copying minors), the output is identical to the plain run.

Confirmation on this exact tree: RUSTFLAGS=-Dwarnings cargo check -p perry --bins; cargo test --release -p perry-runtime 3791 passed / 1 failed (the same #10205 test).

CI attribution (#10217 run 34769800931 vs main's run at b5a82cfeae)

The same failing lint/check/warnings/cargo-test steps and errors, the same native_stack failure, the same four gated gap regressions with identical output, and the same gc-stress failure.

Review notes

A block is skipped only when no census membership query landed in it (every census-built mark is preceded by one) and the census recorded no per-object obligation: pinned, forwarded or pre-marked headers, non-arena, finalize hooks, Error/RegExp/LazyArray dead-payload hooks, raw-f64/holes array layouts, or legacy overflow and wasm-wrapper entries while those tables are non-empty. Allocate-black births are excluded by the bump-offset comparison and block persistence by the recent-window exclusion. Budgeted fulls and minors keep the per-object walk. Page bookkeeping for skipped old blocks goes through the existing unregister_old_block_pages.

Summary by CodeRabbit

• New Features

  • Synchronous full garbage collections can now reclaim eligible untouched memory blocks without scanning every object, improving collection efficiency.
  • GC diagnostics report reclaimed blocks, objects, and bytes when enabled with PERRY_GC_DIAG=1.

• Documentation

  • Updated garbage-collector documentation to explain block-level reclamation, eligibility limits, and diagnostic output.

• Chores

  • Updated the application version from 0.5.1561 to 0.5.1562.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Advanced

Run ID: f8d9cbec-ab3b-4ae5-9dab-7dab8ca5f65a

📥 Commits

Reviewing files that changed from the base of the PR and between 6000a00 and 5f0cade.

⛔ Files ignored due to path filters (1)

• Cargo.lock is excluded by !**/*.lock

📒 Files selected for processing (20)

• CLAUDE.md
• Cargo.toml
• changelog.d/10217-gc-block-granular-sweep.md
• crates/perry-runtime/src/arena/mod.rs
• crates/perry-runtime/src/arena/reset.rs
• crates/perry-runtime/src/arena/walk.rs
• crates/perry-runtime/src/array/element_shape.rs
• crates/perry-runtime/src/array/mod.rs
• crates/perry-runtime/src/gc/cycle.rs
• crates/perry-runtime/src/gc/oldgen.rs
• crates/perry-runtime/src/gc/oldgen/sweep_objects.rs
• crates/perry-runtime/src/gc/tests/block_skip.rs
• crates/perry-runtime/src/gc/tests/mod.rs
• crates/perry-runtime/src/gc/trace.rs
• crates/perry-runtime/src/gc/trace/block_skip.rs
• crates/perry-runtime/src/gc/verify.rs
• crates/perry-runtime/src/object/global_this.rs
• crates/perry-runtime/src/object/global_this_webassembly.rs
• docs/src/internals/garbage-collector.md
• scripts/gc_runtime_root_holders.json

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📝 Walkthrough

Walkthrough

Changes

Block-granular garbage collection

Layer / File(s)	Summary
Census and block-walk infrastructure crates/perry-runtime/src/arena/..., crates/perry-runtime/src/gc/trace..., crates/perry-runtime/src/object/...	Arena cursors now support skipped block indices. BlockCensus records block contents, reachability, and per-object sweep obligations.
Sweep and remembered-set integration crates/perry-runtime/src/gc/cycle.rs, crates/perry-runtime/src/gc/oldgen.rs, crates/perry-runtime/src/gc/oldgen/sweep_objects.rs, crates/perry-runtime/src/gc/verify.rs	Synchronous full cycles skip eligible unreached blocks during remembered-set rebuilding and sweeping. Budgeted cycles and minors continue to walk blocks.
Safety tests and test fixtures crates/perry-runtime/src/array/..., crates/perry-runtime/src/gc/tests/...	Tests cover reclamation, live objects, finalizers, side tables, weak references, sabotage cases, and budgeted full collections.
Documentation and release metadata CLAUDE.md, Cargo.toml, changelog.d/..., docs/src/internals/..., scripts/gc_runtime_root_holders.json	Version records, changelog text, collector documentation, and GC holder metadata describe the implementation and diagnostics.

Estimated code review effort: 4 (Complex) | ~60 minutes

Change: Refactor

Sequence Diagram(s)

sequenceDiagram
  participant FullGC
  participant BlockCensus
  participant RememberedSetRebuild
  participant ArenaSweep
  FullGC->>BlockCensus: collect reachability and sweep obligations
  BlockCensus-->>RememberedSetRebuild: provide unreached block set
  RememberedSetRebuild->>ArenaObjectCursor: skip selected blocks
  FullGC->>ArenaSweep: pass census
  ArenaSweep->>ArenaSweep: reclaim eligible blocks without object walking

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✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch train184s

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