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Robert Allan JamesandClaude Sonnet 5 9eff122090 Fix aarch64 Stadium/COOL O(ncells) scan; rerun std79 DoE clean, 81/81 (FABRIC-3.md §XVI)
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Root cause of the 90+ minute aarch64 VM-birth stall found in §XV: stadium_admit()'s
eviction-fallback scan iterated the entire stadium_ncells array filtered by owner,
not the calling VM's own resident cells as its own doc comment claimed. Combined
with stadium_grant_quota() always splitting from Hera's shrinking free list and
stadium_word_dispatch() calling stadium_admit() per distinct word a VM's capsule
executes, this compounded into a real O(n) blowup — catastrophic specifically on
aarch64 because its -m 4096 (vs 1024 on amd64/riscv64) inflates the kmalloc heap
kmalloc_init() bisects down to, which inflates stadium_ncells 4x (335,544 vs 83,886
cells, measured from boot logs).

Fixed by threading a real per-VM doubly-linked resident-cell list
(StadiumVMQuota.resident_head + stadium_resident_next[]/stadium_resident_prev[])
so the fallback scan is bounded by that VM's own resident count, not the global
cell array size.

Verified with a full rerun of the 3x9x3 std79 DoE campaign from scratch: one
continuous boot per architecture, all 9 identities simultaneously live throughout
(the 3-boot aarch64/riscv64 batching workaround is no longer needed). 81/81 trials
correct, 0 mismatches, DOE-RUN header sequence md5-identical across all three raw
logs. Identity 04's attach on aarch64, which stalled 90+ minutes before, now
completes in ~34s; full boot-to-DoE-complete in ~290s.

Corrects an earlier misreading (carried into §XV, std79-doe.fth's comments, and
the project memory note) that described the symptom as a runaway "335,000+ cycles"
dispatch counter — those were cell array indices, not an event count.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EXieurDfDSsDFdnSyusuWo
2026-09-11 16:37:44 -04:00
Robert Allan JamesandClaude Sonnet 5 e2abc56306 3(arch) x 9(identity) x 3(rep) randomized full-factorial std79 DoE: 81/81 correct (FABRIC-3.md §XV)
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Formal successor to §XII's ad hoc exerciser campaign, requested as a
genuine randomized full-factorial design matching this project's own
DoE methodology (capsules/doe.4th's Fisher-Yates shuffle), and written
entirely in FORTH per explicit request -- not host-orchestrated shell
scripting.

experiments/std79-doe/std79-doe.fth: builds a 27-cell (9 identity x 3
replicate) run matrix, Fisher-Yates shuffles it with a fixed seed
(matching doe.4th's own default), then dispatches each of the 24
exerciser test cases directly into the target identity's own live VM
via VM-EXEC -- no console USE redirection, no per-trial host
interaction. The zuse case runs as directly-compiled native code
(RUN-TEST-NATIVE) rather than VM-EXEC targeting "Hera" herself:
VM-EXEC's own vm_state_push/pop only saves rsp/exit_colon/ecw_nesting,
not input_buffer/input_pos, so a self-targeting call while this
capsule's own vm_interpret call is still mid-line would risk exactly
the class of bug the idle-tick reentrancy guards exist for.

amd64: all 27 trials ran with all 9 identities simultaneously live in
one boot -- clean, zero mismatches.

aarch64: hit a real, uninvestigated bug attaching all 9 simultaneously
-- the 6th live VM's birth stalled for 90+ minutes at 100%+ CPU with a
Stadium COOL-dispatch counter already at 335,000+ cycles, versus tens
of thousands at the same checkpoint for earlier identities. Not
root-caused here (flagged in FABRIC-3.md for later); worked around by
splitting into 3 boots of 3 simultaneously-live identities each, every
boot sharing the same seed so the master 27-slot shuffle is identical,
filtered per boot by a new ACTIVE-LO/ACTIVE-HI range
(EXEC-STD79-DOE's signature: seed lo hi -- ). run_id is always the
slot's true position in the master shuffle, so trial order stays
comparable across boots -- standard DoE blocking.

riscv64: same 3-boot pattern, clean.

Grand total: 81/81 trials correct, 0 mismatches, across all three
architectures, all nine identities, all three replicates.

Also flagged (FABRIC-3.md §XIV, not fixed): attaching several WIREBIND
identities near-simultaneously (whether via rapid hotplug or all
present from boot) causes the kernel to silently detect only some of
them -- confirmed at the host/QMP level that every device was genuinely
present. Worked around throughout this campaign by attaching one
identity at a time with confirmed waits; real hardware hotplug could
hit the same gap, so it's a genuine robustness concern, not just a
test-harness inconvenience.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EXieurDfDSsDFdnSyusuWo
2026-09-11 13:59:32 -04:00