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Malte Ubl
def6f86a0e
Nearly every long-lived object becomes a cycle candidate once, soon after it is built: the constructing frame's release leaves it held only by the structure it was stored into. A nursery pass then walks it (about 75 ns per object), it survives, and it is re-buffered for the mature level, whose next pass walks it again. In tsc-ts single-threaded, nursery passes walked 6.0M objects on Excalidraw and 36.5M on Sentry and freed 7%; 99% of what they walked was promoted. Most of that walking goes to types whose objects never die in a young cycle: SymbolLinks, NodeLinks and Symbol were 2.0M of Excalidraw's candidates and the collector freed none of them, while young garbage comes from a few types (inference contexts and mappers, closures, some arrays). Types with a collector yield under 0.5% are 42-55% of what nursery passes walk. So the collector now keeps per-thread statistics per type and level. Each ScrCycType gains a `kind` index: emitted descriptors number themselves from 32 (FIRST_EMITTED_CYC_KIND / SCR_CYC_KIND_EMITTED), the runtime's own families have fixed kinds below that, 0 keeps no statistics. For the nursery and mature levels, a pass counts the candidates of each kind it walks and the objects of each kind it frees. After every 8192 walked candidates a kind bypasses that level for the next window if fewer than 1 in 128 of them were freed. A release that buffers an object at a level its type bypasses promotes it past the level first, and a nursery pass that re-buffers a survivor into a bypassed mature level moves it to the old level. One candidate in 16 stays put, so the yield keeps being measured and a type whose objects start dying young again is walked again after one window. Only the generation an object is judged in changes. Any assignment is sound (a restricted pass counts edges from older objects as external), a bypassing candidate stays buffered, and full passes walk everything they did before, so the old level's bounds hold unchanged. Cyclic garbage made only of objects of a bypassing type waits for the next pass at an older level. Programs that never complete a window (8192 walked candidates of one type) are collected exactly as before. The descriptor layout is part of the emitted-code/runtime ABI, so the program-object marker moves to scr_runtime_abi_v12. Pass log (instrumented build, single-threaded, one run each, with the preceding null-slot change): all collector passes Excalidraw 606 -> 313 ms (nursery 435 -> 153), TypeORM 629 -> 383 ms, tsc-ts self-check 377 -> 215 ms, Sentry 7.61 -> 5.75 s (nursery 2.92 -> 1.04 s, mature 1.17 -> 1.02 s; the full pass is unchanged at 3.6 s). tsc-ts (Linux sandbox, interleaved, medians; 10 rounds, Sentry 5 rounds pinned to 8 CPUs; both changes against int/best-v6): single-threaded Excalidraw -8.0%, TypeORM -4.2%, self-check -4.3%, Sentry -5.3%; --checkers 8 -12.2%, -0.8%, -2.3%, -1.6%. Peak RSS -0.8% to +0.6%. Diagnostics identical. Tests: test_cycle gains check_nursery_bypass, check_mature_bypass and check_rebuffer_past_mature (a test-only entry point, scr_cyc_pass_at under SCR_CYC_TESTING, runs passes at exact levels); each fails under the corresponding mutation (no bypass, a sticky decision, no sampling, no freed or walked counts, a bypassing candidate left unbuffered, survivors re-buffered into a bypassed level). Corpus 4690 builds a long-lived declaration graph large enough for both levels to bypass and lets objects of the same classes die in cycles; under --sanitize the exit RC audit proves they are reclaimed.