Lift OTP's `exit(Pid, shutdown)` + child-spec `shutdown` wholesale.
scheduler / runtime
- `request_shutdown(pid)`: the polite stop. A target trapping exits gets an
`ExitSignal { reason: DownReason::Shutdown }` on its trap inbox and keeps
running; a non-trapping target is stopped as by `request_stop`, which is
now documented as the hard stop (`exit(Pid, kill)`). Dead pid: no-op.
- `RuntimeHandle::request_shutdown` for the off-runtime (signal thread) path;
`from == ROOT_PID` there.
- `DownReason::Shutdown` — appears only in ExitSignal, never in Down (a
complying target exits *normally*).
supervisor
- `ChildSpec::shutdown(Shutdown::{BrutalKill, Timeout(d), Infinity})`,
default Timeout(5s). Every supervisor-initiated stop (ordered shutdown and
OneForAll/RestForOne sibling cycling) is: request_shutdown → await the
child's Signal up to the grace → request_stop → await. Sequential, reverse
start order.
- The supervisor traps exits; a Shutdown ExitSignal runs the ordered
shutdown and `run()` returns normally, so `request_shutdown(root_sup)`
tears a whole tree down top-down with each child's grace period.
- FIX: a hard `request_stop` on a supervisor previously orphaned its
children (the ordered shutdown lived after the loop, and the unwind
skipped it). `Live` (the by_pid map) now carries a drop guard that
fire-and-forget hard-stops live children when unwinding.
gen_server
- `GenServerCtx::trap_exit()` opt-in in `init`; the trap inbox becomes arm 0
of the loop's select. Shutdown ExitSignal → `handle_shutdown() ->
ShutdownAction::{Exit, Continue}` (default Exit: loop breaks, `terminate`
runs on the normal path and may block). Other ExitSignals →
`handle_exit(sig)`.
- `GenServerCtx::stop_handle() -> StopHandle`, `stop()` ends the server
after the current message with a *normal* exit — the missing
`{stop, normal, State}`; `request_stop(self_pid())` was the only self-exit
and it is abnormal (Transient restarts it).
- `GenServerRef::shutdown()` / `gen_server::shutdown(name)` now go through
`request_shutdown`.
Tests: tests/shutdown.rs, tests/supervisor_shutdown.rs,
tests/gen_server_shutdown.rs. Full suite green; fmt + clippy --lib clean.
Per-actor stack shapes on every spawn surface (SpawnOpts stack_reserve/
guard_size, Config defaults, pool rule: only default-shaped recycle);
sampled stack high-water + MADV_FREE shrink at actor-park (THRESHOLD
256 KiB, COOLDOWN 64 parks, redzone 1 page); pool-recycle MADV_DONTNEED
above the retained 64 KiB entry end; SIGSEGV overflow diagnostics
(two-tier: in-guard definitive / 1 MiB overshoot 'stepped over', prior
handler chained for foreign faults) with per-scheduler sigaltstack; and
the per-actor introspection surface (ActorInfo.stack: reserve, guard,
sampled depth, parks_since_shrink, shrinks).
Amendments ratified during implementation, for the RFC changelog:
- DEFAULT_STACK_GUARD 64 KiB -> 1 MiB, following the kernel's post-Stack-
Clash stack_guard_gap convention; PROT_NONE width is VA-only and free.
- §7's motivating segfault was a cargo-vendored gz build, not SQLite as
the RFC text says (cc-built C lacks -fstack-clash-protection; distro
libraries have it — the risky class is vendored builds).
- §4 hibernate() deferred to the jar (bolt-on: force-flag on the §3
shrink path, ~10 lines when wanted).
Gates (jobrunner box, 2026-08-08): reclaim gate PASS at c3 and again at
tip (3.0 MiB LazyFree -> kernel reclaim -> Rss to one live page ->
re-spike bit-identical, live data intact; MADV_PAGEOUT stands in for
memcg — cgroup2 is RO in the job container — driving the same reclaim
path). E1 interleaved A/B vs v0.5.0: every ka cell (the E1 subject)
within +0.3..+2.9% at tip; close-mode control cells within noise except
t8-c4 close, which is bistable (~40-44k vs ~46-49k modes for BOTH
variants, base self-disagrees by 11% across rounds); 6 rounds across two
runs are inconclusive there and a 10-round focused run is noted in the
handoff as deferred follow-up, accepted for this release.
No breaking API changes since v0.5.0: SpawnOpts fields and ActorInfo
gained members (exhaustive-construction downstream will need the new
ActorInfo.stack field; urus does not construct it).
- introspect::StackInfo { reserve, guard, depth_high_water,
parks_since_shrink, shrinks } as ActorInfo.stack; re-exported at crate
root beside ActorInfo.
- All reads lock-free: geometry from the c6 diag slot atomics, depth =
top - hwm (the §2 sampled high-water; doc spells out sampled-not-exact
and that 0 means never-descheduled-at-depth), counters straight off the
§3 atomics. Coherence for the incarnation rides read_slot's existing
generation check, same as overruns/messages_received.
- Slot::stack_introspect(): one pub(crate) tuple accessor beside the other
counter accessors.
- Exact RSS deliberately absent per RFC (mincore = debug tooling only,
never a runtime path); stack_shape(pid) untouched (cold-lock exact
variant from c2).
- tests/introspect.rs: defaults surface (64 KiB reserve / 1 MiB guard /
sampled ~32 KiB depth / gate park counted / zero shrinks) + live shrink
counters (spike visible pre-shrink; shrinks>=1, cooldown counter reset,
hwm reset after crossing COOLDOWN) read mid-run -- post-join the slot
reclaim correctly hides the incarnation, which the first draft of the
test learned the hard way.
FLAGGED (Claude-solo calls):
- Nested StackInfo struct over five flat ActorInfo fields (grain break;
the five fields are one concern and ActorInfo is already 12 fields).
- Field names reserve/guard/shrinks (RFC says stack_reserve/stack_guard/
shrink count; the stack_ prefix is redundant inside StackInfo).
- src/signal.rs: process-global SA_SIGINFO|SA_ONSTACK handler installed once
at runtime::init (before any scheduler thread -> unracing PRIOR save);
per-scheduler-thread 64 KiB sigaltstack registered at schedule_loop entry
(a guard hit leaves no stack to handle on). Async-signal-safe throughout:
classification is plain loads (const-init TLS Cell + slot atomics), print
is fixed-buffer itoa + one write(2), death is SIG_DFL + refault at the
same instruction (core-dumpable, correct wait status).
- Two-tier classification (agreed): in-guard = definitive; OVERSHOOT window
below the guard = 'unprobed (FFI?) frame stepped over it' probable
attribution -- the RFC's motivating incident (cargo-vendored gz, not
SQLite as the RFC text says) faults there under a small guard. Pure
classify() fn, 5 adversarial units incl. saturation at low addresses.
- DEFAULT_STACK_GUARD 64 KiB -> 1 MiB (agreed): kernel stack_guard_gap
anchor post-Stack-Clash; PROT_NONE is VA-only (no RSS, no page tables,
no overcommit charge) so width is free at any actor count.
- Unclassified faults reinstate the PRIOR sigaction and refault (agreed):
std's own OS-thread overflow diagnostics survive our presence.
- Slot: diag_{stack_top,stack_reserve,stack_guard,pid} atomics written in
install_actor pre-publish; readable without the cold lock (Stack lives
under it); only consulted while CURRENT_SLOT points at the slot, so
never stale where read. preempt::current_slot_ptr ungated from
smarm-causal (now also the classifier's anchor).
- build.rs + cc (agreed Q3): canary/canary.c, 96 KiB local touched low-end
first, -fno-stack-clash-protection pinned so hardened toolchains don't
probe the canary into uselessness.
- tests/stack_diag.rs: subprocess x4 -- Rust recursion tier-1; FFI canary
tier-1 at defaults (1 MiB guard catches the jump); tier-2 at guard=4 KiB
('stepped over', reproduces the incident); clean at reserve=256 KiB
(the §1 knob is the fix, same frame).
FLAGGED (Claude-solo calls):
- OVERSHOOT_SLOP = 1 MiB (matches guard default/kernel gap; beyond it
attribution would be dishonest).
- Altstack 64 KiB, mmap'd once per OS thread, never freed (bounded by
thread count; reused across run()s via TLS flag).
- Foreign-fault reinstate permanently deregisters our handler; accepted --
the process is dying either way.
- Diag geometry as 4 slot atomics (install-time cost only) over a per-switch
TLS snapshot (hot-path stores).
- stack::retain_range: pure checked span fn (retain page-up = zap less;
None when retain covers the reserve, so the 64 KiB default config never
pays a syscall) + 6 adversarial units mirroring shrink_range's.
- Stack::recycle_zap: advisory MADV_DONTNEED of [usable_base, top-RETAIN);
stack is unowned at the call site, synchronous eager zap races nothing.
- recycle_stack: zap OFF-LOCK before pool admission (acquire_stack's
no-syscall-under-the-pool-lock invariant); rare cap-overflow pays a
wasted zap ahead of munmap, accepted over a second lock round-trip.
- pub const RECYCLE_RETAIN = 64 KiB beside the shrink knobs, ratified-as-
constant rationale in doc.
- tests/stack_recycle.rs: mincore-based exact-zero-resident assert over
the zap span. smaps was tried first and over-counts: a neighboring rw
anon VMA can merge flush against the stack top (observed once under the
full-suite run); the PROT_NONE guard pins the usable base exactly.
FLAGGED (Claude-solo calls):
- RFC §6 'above the bottom RETAIN' is direction-ambiguous in address
terms; implemented as retain the ENTRY end (highest addresses, the
pages the next actor faults first), zap the cold deep span below.
- Const named RECYCLE_RETAIN (RFC says RETAIN) to sit beside SHRINK_*.
hwm: AtomicUsize lands beside sp on the slot: the single context-save
site min-updates it (one branch + at most one Relaxed store into the
line the sp store just dirtied), install resets it to the fresh top.
Advisory by construction — correctness never depends on it. The mod-doc
ordering chain gains a line: hwm piggybacks the existing
Relaxed-store-before-Release pattern and adds no edges.
Shrink hook in the YieldIntent::Park arm only, before the park_return
Release transition — the owned window (obligation 1's assert-comment at
the site): after the sp store, before Parked is published, scheduler on
its own stack, actor saved and unstealable. It runs on both arms of the
park_return race (a consumed unpark flag means one wasted-but-harmless
madvise). The preempt/yield path deliberately never checks: §4's
bounded, self-healing leak under saturation, when syscalls are least
affordable.
SHRINK_THRESHOLD = 256 KiB and SHRINK_COOLDOWN = 64 parks are pub
constants with the ratified doc rationale, not Config fields. The freed
span is shrink_range(hwm, sp, page): whole pages of [hwm, sp − 1-page
redzone), rounded inward, checked arithmetic — adversarial inputs
collapse to None (obligation 2). MADV_FREE marks lazily; the kernel's
reclaim-under-pressure IS the hysteresis, cancel-on-write is the safety
net. parks_since_shrink + shrink_count ride the slot for the cooldown
and the future introspect surface.
Tests: 7 adversarial shrink_range units (inverted/empty spans, redzone
underflow, unaligned ends, sp-crossing sweep); integration — 8 MiB
reserve, ~3 MiB spike sampled via yield-at-depth, parks gated on
introspected Parked state past the cooldown, then ≥ 2 MiB LazyFree
asserted inside the stack's smaps range with live data intact; and the
inverse guard — a shallow never-spiking actor ends at exactly 0
LazyFree (also proves the parser isn't vacuously zero via the first
test).
SpawnOpts { stack_reserve, guard_size } with Option<usize> fields, None
resolving to the Config defaults at spawn time — a deliberate deviation
from the RFC's plain-usize struct so struct-update syntax works without
a runtime handle in scope. Threaded across the five surfaces:
spawn_with, spawn_under_with, spawn_addr_with,
GenServerBuilder::stack_opts (mirrored on NamedGenServerBuilder), and
gen_statem::spawn_with (gen_statem has no builder, so the opts ride a
_with variant — Claude-solo surface call, flagged for review). Existing
spawns forward defaults; no call-site churn.
introspect::stack_shape(pid) pulled forward (agreed) as the first slice
of the RFC 019 introspection surface, giving tests an observable.
Tests (tests/spawn_opts.rs): override/partial-override/rounding on each
surface; obligation 4 from the outside — a dead custom stack is never
handed to the next default spawn (LIFO pool would expose it), and the
reverse (default stacks ARE recycled); 8 MiB reserve behaviorally
permits ~1 MiB recursion. Also: silence unused-Result in the c1
runtime test (join now unwrapped).
Stack takes an explicit (reserve, guard) shape, both page-rounded and
stored; usable_base derives from the stored guard. Guard default raised
4 KiB -> 64 KiB (DEFAULT_STACK_GUARD): probestack makes one page enough
for Rust frames, but an unprobed C frame can leap a page in one sub rsp
— the motivating SQLite segfault. Reserve default stays 64 KiB
(DEFAULT_STACK_RESERVE); ACTOR_STACK_SIZE retired.
Config::{stack_reserve, stack_guard} thread the runtime defaults into
RuntimeInner pre-rounded. All acquisition/recycling now goes through
acquire_stack/recycle_stack carrying the pool rule: only default-shaped
stacks are pooled (pooled ⇒ default-shaped by induction); custom shapes
mmap fresh and munmap at death. Pool lock still dropped before any mmap.
No public spawn API change (SpawnOpts is the next commit).
Tests: shape rounding + accessors, wide-guard faults at both ends
(subprocess), Config::stack_reserve permits >64 KiB recursion that
previously could only segfault.
run_experiments snapshots the site registry once at entry. stage-x is
registered lazily (first causal_site! execution in the worker), so on a
1-core box the snapshot deterministically wins whenever a sibling test
has already paid the tsc_hz calibration — stage-x missed the sweep and
the summary assert tripped (silently, pre-propagation; the earlier
cascade attribution was incomplete). The worker now signals after its
first site entry and the test waits on it before starting the sweep.
Jarred separately: the lazy-registration trap is a lib UX hazard worth a
doc note or warm-up guidance.
A fresh/reused slot started with causal_delay=0 and causal_parked=true:
the first resume then 'forgave' the entire monotone global backlog, once
per spawn, booked as park forgiveness. Under close-mode conn churn (~95k
spawns/s) that is millions of phantom forgiven ms per 700ms window, even
in 0% cells — the books could not balance under actor churn while
ka-mode stayed plausible (few spawns). Impacts were unaffected: the
first resume always precedes the first check, so nobody ever spun.
reset_counters now installs Coz's new-thread rule: causal_delay starts
at the current global ledger and causal_parked starts false — a newborn
neither owes nor is forgiven the process's history, and delay injected
while it sits spawn-queued (runnable, not blocked) is owed and paid at
its first check, the semantics audit_zero_pct_window_absorbs_leftover_
debt pins. That test (born failing, unmasked by the run() propagation
fix) and the new actor_churn_between_experiments_forgives_nothing
regression test both go green.
The trampoline caught the root's panic, recorded it as Outcome::Panic on
the slot, and run() dropped the initial handle without reading it — every
assert inside run(), the standard test-suite pattern, was silently
vacuous (found live: a failing-first test passed). run() now reads the
root outcome before the handle drop and resume_unwinds the payload after
full teardown, so a caller's catch_unwind leaves the Runtime reusable;
Exit and Stopped return normally. The payload message is printed before
re-raising (the throw-site hook output was suppressed in-actor).
Correct the two tests this unmasked, both born failing and never run:
the select loser-arm test kept a closed arm in the set (the documented
closed-arm rule: a closed arm reports ready forever — observe the
disconnect and drop it); the send_after-to-dead test expected Ok(None)
from a closed+empty channel (documented: Err(RecvError), which proves
nothing-delivered even more strongly).
The probe now prints eff+offcpu next to eff — attributed plus the
counted runnable off-CPU gaps over ground-truth in-site time — the
per-window check that the located mechanism accounts for the whole
residual (~1.00 = books closed, no remaining silent loss). Audit line
gains the offcpu column, same delta-terms convention as the lib
renderer. Header doc rewritten from hypothesis to resolution.
GPU sweep decomposed the ~23ms/700ms @50 injection deficit: every
ledger bucket is ~zero (drop park 0, discards 0, drop yield ~0.3ms),
books balance at absorbed+forgiven = 4x injected in all 48 cells, and
the 0%-cell contamination signature is absent. The probe pins the
residual: eff 0.933-0.943, a constant 22-27µs missing per site entry
= ~4.9 slice-expiry yields/entry x ~5.6µs runqueue wait. The
"deficit" is runnable off-CPU time inside the site — wall time the
probe's ground truth counts but on-CPU attribution correctly skips
(Coz model: speeding the site's code does not shrink queue-wait).
Measure-only reclassification, no behaviour change: a yield in the
target site stashes (tsc, experiment epoch) on the slot; the next
on_resume counts the gap into OFFCPU_IN_SITE_{CYCLES,N} (would-be
delta terms, MAX_SAMPLE_CYCLES-capped) iff the epoch still matches
and the word is live — a gap straddling end()/a same-word begin()
(live in the probe's 50,50 schedule) is dropped, never a leaked
cooldown. Parks excluded: blocked time is forgiveness territory.
New offcpu column in render_ledger_audit; LedgerCounters and
ExperimentResult grow the two fields. Fidelity footer now states
the on-CPU basis (deliberate wording change to the pinned summary;
the substring pin test still holds). +2 tests (counted gap; epoch
straddle) + render assert.
- causal_pipeline: SMARM_CAUSAL_AUDIT=1 appends render_ledger_audit()
after the summary; pinned summary format untouched.
- causal_attrib_probe: per-pct audit line (absorbed/forgiven/drops/
discards) under the existing eff line, so in-site-vs-attributed and
the loss buckets land in one place for the sweep.
1-core smoke (work + wide): books balance — absorbed = 2x injected and
forgiven = 2x injected, i.e. owed = injected x (N-1) with N=5 actors,
zero outstanding. drop park = 0 even in wide mode (the bottleneck's
queue is never empty, so its in-guard recv never parks); drop yield is
~1500 events but ~0.1ms per window, confirming slice-expiry yields
sample at their own checkpoint. Deficit decomposition needs the
parallel box.
Measure-only counters for the deficit hunt (~23ms short per 700ms window
at 50% on the bottleneck site; superlinear vs 25%). Nothing here changes
injection or absorption; the sweep decides the fix.
Buckets, windowed per cell into new ExperimentResult fields (audit
snapshot taken at end() — spin/attribution freeze there, forgiveness
does not):
- spin_absorbed / park_forgiven: where owed delay actually went. Spin
during a 0% cell is the baseline-contamination signature — leftover
debt from a prior window being paid in a later one (checks gate on
the experiment word, so cooldowns pay nothing and debt carries over).
- drop_park / drop_yield (+counts): the deschedule path flushes no
sample tail — an in-target-site park or yield silently loses
[last sample -> now]; on_resume re-arms before the actor runs again.
New on_deschedule hook in all three intent arms (real park; explicit/
slice-expiry yield; requeued park counts as yield — it never blocked).
Slice-expiry yields sample at the descheduling checkpoint, so a fat
yield bucket points at explicit yield_now or requeued parks.
- discard_overmax (+count, in would-be delta terms so columns compare
against injected_cycles) / discard_unarmed: the attribute() clamps,
previously silent.
LedgerCounters + ledger_counters() expose cumulative totals (tests,
run-level prints); render_ledger_audit() is the per-cell companion to
render_summary, which stays byte-identical (pinned). ExperimentResult
now derives Default so literals survive future audit-field growth.
Tests: +7 (spin counted, forgiveness counted, in-site park drop, in-site
yield drop, overmax discard, 0%-window leftover absorption — synthesized
deterministically via inject_delay_cycles_for_test with no experiment
active — and the audit render). 22/22 causal.
One unconditional footer line whenever there are results:
"note: impacts are lower bounds — undershoot grows with speedup pct;
rankings unaffected" — surfacing the RFC 007 Validation fidelity statement
where users actually look, instead of only in the RFC. Wording pinned by
the summary test.
send_after_wall / send_after_named_wall (+ Timers::insert_send_wall) arm a
message-delivery timer that opts out of the RFC 007 virtual-time shift and
fires at its raw deadline regardless of injected delay — the Send-reason
sibling of sleep_wall, closing the jar item whose substrate efbc254 landed.
For deadlines that reflect the outside world (protocol timeouts, wall-clock
schedules) rather than workload pacing. cancel_timer is anchor-agnostic and
unchanged; without the feature the API exists and is identical to send_after.
The gen_server timer layer (send_after_to, RFC 015 §5) deliberately stays
virtual-only — an opt-out there means new options on the gen_server/statem
timeout API, out of scope for now.
Tests: wall send fires at raw deadline while a virtual sibling shifts;
cancel on a wall send with debt outstanding; featureless delivery/cancel
smokes through the public named API. 15/15 causal, 34/34 binaries both
feature configs, lib clippy clean both.
Occupancy probe on 24 cores: δ = 0.3µs/item (0.1% of the serialized
path); wide guard leaves the @50% cell unchanged. The +84-vs-+100
shortfall is controller-side (injected 327ms of the ideal 350ms over
the 700ms window, plus ~3% real-rate dip during experiments), not
unguarded stage time. urus's ~70µs/request remainder remains the
guard-placement case; the occupancy probe discriminates the two.
SMARM_CAUSAL_MODE selects the reserve stage's guard placement:
work (default, unchanged) | wide (guard over recv+work+send, the whole
serialized per-item path) | occupancy (no experiments; per-segment
timing of reserve's loop at baseline, reporting the unguarded
remainder δ and the impact ceiling it implies).
Discriminates the two candidate explanations for the demo's +84-vs-+100
@50% shortfall: physical recv/send time outside the guard (occupancy
sees δ≈30µs, wide recovers ~2x) vs. injection-side credit loss
(occupancy sees δ≈0, wide caps at ~+84 too — guard cadence identical).
New timer anchor: insert_sleep_wall / scheduler::sleep_wall (exported) opt a
Sleep entry out of the RFC 007 virtual-time shift, so it fires at its raw
deadline regardless of injected delay. Featureless config is unchanged (the
API exists but is identical to sleep).
The causal controller's window/cooldown sleeps and the tsc_hz calibration
sleep use it on the actor path (the OS-thread path was already wall). This
fixes the controller's own sleeps dilating under its own injection —
experiment windows stretched ~2x at 50% speedup (337ms -> 646ms injected/
window). Deltas were rate-normalized so results were unbiased; this fixes
sweep cost, not bias. The general wall-anchored-timer-semantics jar item
(user-facing opt-out) remains open; this lands the substrate.
Test: wall_timer_ignores_injected_delay — wall entry fires at raw deadline
while a virtual sibling in the same heap shifts. 13/13 causal, 34/34
binaries both feature configs.
Injected delays dilate virtual time for the workload, but timer deadlines
stayed wall-anchored: a sleep or receive-timeout fired early in virtual
terms, so timeout/retry behaviour sped up relative to the dilated world
(v1 known gap #1).
Every heap Entry now carries delay_stamp — the global delay ledger at
(re-)queue time, cfg-gated on smarm-causal. pop_due converts any debt
accrued since the stamp to wall time (tsc_hz) and shifts the effective
deadline; a not-yet-due entry is re-queued at the shifted deadline with a
fresh stamp, so it keeps chasing delay injected while it waits. seq is
preserved across re-queues, keeping send_after cancellation identity
intact (cancelled entries are discarded before any shift). Zero debt is
byte-identical to the old path; peek_deadline may under-report, costing
one spurious scheduler wake per injected chunk (documented).
This also makes the park-gated resume credit *correct* rather than
forgiving for sleepers: a sleeping actor now physically pays its debt by
sleeping longer, so the on_resume fast-forward reflects real payment
(sleeping_actor_pays_injected_delay pins this end-to-end through the
runtime).
New test hooks: inject_delay_cycles_for_test (deterministic ledger
driver, eagerly TSC-calibrating so conversion never stalls a scheduler
loop) and cycles_to_duration. The ledger is process-global, so the
delta-sensitive causal tests now serialize on a shared test mutex — they
were racy under the parallel test harness before this, in principle.
Samples were taken only when maybe_preempt's cold block happened to fire
in-site, so the interval between the last check and SiteGuard drop was
discarded on every site entry. Measured live on the 24-core box:
22-29us lost per entry, a constant attribution efficiency of ~0.93-0.94,
which under-reported every impact (+83.5% where theory says +100%; the
observed shortfall fits 1/(1-pct*eff)-1 at both 25% and 50%).
SiteGuard enter/drop now call site_transition(): leaving the target site
flushes the pending interval into the ledger (sample-only, never spins,
so safe under no-preempt regions); entering the target site re-arms the
sample clock so pre-site time is never attributed (the symmetric
over-attribution). Winner attribution is factored into attribute(),
shared by the cold check and the flush, with the same interval clamps.
Adds examples/causal_attrib_probe.rs (ground-truth in-site time vs
ledger attribution, the probe that confirmed the leak) and the
site_boundaries_flush_tail regression test (a site entry that never
hits a cold check must still be attributed). Also gates causal_probe
on smarm-causal in Cargo.toml - it never was, so featureless builds
of the examples were broken.
causal_site! scoped site guards per actor slot, progress! throughput
points, and a Coz-style virtual-speedup engine hooked into
maybe_preempt's amortized cold block: target-site samples grow a global
delay ledger; bystanders spin-absorb their debt at the next causal
check, with timeslice extension so injected delay is not charged
against the slice.
Resume credit (Coz's blocked-thread rule) is gated on a causal_parked
slot bit set only by a real park: crediting on every resume made any
yield-cadence actor delay-immune and every experiment inert (found
live on a 24-core run — dead-flat deltas across all sites).
Report normalization uses a measured TSC frequency (~50ms calibration
on first use) instead of the crate-wide 3 GHz assumption, which
uniformly inflated impact numbers on a 3.7 GHz box. impact_pct() is
the machine-readable form of the summary for programmatic checks.
examples/causal_pipeline.rs burns fixed *work* (calibrated LCG loop),
not fixed wall time — a timed busy-wait absorbs injected delay into
its own budget and reads as a no-op. Self-checking: exits nonzero if
causal separation fails; skips the verdict below 4 cores. Validated
on a 24-core box: reserve (true bottleneck) +29.3%@25/+83.5%@50;
serialize and background-compaction ~0%.
Known v1 gaps (jar): timer-heap deadlines unshifted, no-check!/no-alloc
actors undelayable, multi-scheduler coherence best-effort Relaxed,
off-CPU blame punted, Instant::now() uncorrected.
Zero-cost with the feature off; clippy -D warnings clean both ways;
full suite green with and without smarm-causal.
claude