Files
smarm/Cargo.toml
T
claude-asm-audit bf55cef3e3 perf(run_queue): flip default backend rq-mutex -> rq-mpmc
Evidence (history.md session 5, findings 10-11, 20-core jobrunner run):
rq-mutex collapses with thread count on queue-heavy load (yield-storm
6.9x slower than striped at 20T; attributed cause of the baseline's
multi-thread regression on yield_many/chained_spawn), while rq-mpmc is
best-or-close everywhere: best 1-thread, best slot-on ping-pong
(1237us vs mutex 6754us at 20T), -23%/-41 cyc per yield roundtrip on
real hardware (single-core switch_cost, interleaved). rq-striped
remains the churn-heavy many-core option, selectable per build.

Docs + compile_error hints in run_queue.rs updated to name rq-mpmc as
the default. slot_state.rs untouched, no loom-relevant changes; lib
(60) + scheduler/channel/supervisor/park_wake/wake_slot/preempt (41)
pass under the new default.
2026-08-21 12:22:46 +00:00

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[package]
name = "smarm"
version = "0.7.0"
edition = "2021"
rust-version = "1.95"
[lints.rust]
unexpected_cfgs = { level = "warn", check-cfg = ["cfg(loom)"] }
[lints.clippy]
# Library code must never hide a panic behind unwrap/expect. Both are denied; an
# intentional panic is written explicitly as `match { Err(e) => panic!(..) }`.
# panic!/unreachable! are deliberately left un-linted as the blessed explicit
# form. Enforced on the library target only (`cargo clippy --lib`); tests and
# examples unwrap freely and are not gated.
unwrap_used = "deny"
expect_used = "deny"
[features]
default = ["rq-mpmc"]
smarm-trace = []
# RFC 007: native causal profiling. Zero cost when off (cf. smarm-trace): the
# hook in `maybe_preempt` and the resume-path fast-forward compile away; the
# two Slot ledger fields exist regardless and stay 0 (budget_cycles precedent).
smarm-causal = []
# RFC 016 Chunk 2: cycle-accurate per-actor time-budget accounting. Off by
# default — it costs two extra RDTSC reads per actor resume on the hot path
# (D6). The `ActorInfo.budget_cycles` field exists regardless; it just stays 0
# unless this is enabled.
budget-accounting = []
# RFC 016 Chunk 4: the live observer gen_server (src/observer.rs). Off by
# default (DECISION D10) — the read primitive (Chunks 1–3) is always present
# and unflagged; only the optional gen_server transport sits behind this, so a
# release build pays nothing for an observer it never starts.
observer = []
# Run-queue selection: exactly one, compile-time (see src/run_queue.rs).
# Non-default variants need --no-default-features (features are additive).
rq-mutex = []
rq-mpmc = []
rq-striped = []
[build-dependencies]
cc = "1"
[dependencies]
libc = "0.2"
[target.'cfg(loom)'.dependencies]
loom = "0.7"
[dev-dependencies]
libc = "0.2"
tokio = { version = "1", features = ["rt", "rt-multi-thread", "macros", "sync", "time"] }
[profile.dev]
panic = "unwind"
[profile.release]
panic = "unwind"
lto = "thin"
codegen-units = 1
[[bench]]
name = "primes"
harness = false
[[bench]]
name = "multi_scheduler"
harness = false
[[bench]]
name = "general"
harness = false
[[bench]]
name = "smarm_favored"
harness = false
[[bench]]
name = "tokio_favored"
harness = false
[[bench]]
name = "rq_micro"
harness = false
[[bench]]
name = "rq_runtime"
harness = false
[[bench]]
name = "switch_cost"
harness = false
# RFC 016 Chunk 4 — the live observer dump. Needs the optional gen_server.
[[example]]
name = "observer"
required-features = ["observer"]
[[example]]
name = "causal_pipeline"
required-features = ["smarm-causal"]
[[example]]
name = "causal_attrib_probe"
required-features = ["smarm-causal"]
[[example]]
name = "causal_probe"
required-features = ["smarm-causal"]