benches: expose preemption knobs + sweep runner
Config API changes (src/preempt.rs, src/runtime.rs):
- preempt: promote ALLOC_INTERVAL and TIMESLICE_CYCLES from bare consts to
DEFAULT_ALLOC_INTERVAL / DEFAULT_TIMESLICE_CYCLES; store active values in
thread-locals set on each actor resume so multiple runtimes can use
different settings concurrently.
- runtime: add alloc_interval / timeslice_cycles fields to Config; add
Config::alloc_interval(n) and Config::timeslice_cycles(c) builder methods;
thread the values through RuntimeInner to the reset_timeslice() call in
schedule_loop.
Bench changes:
- Add bench_cfg(threads) helper to general/tokio_favored/smarm_favored that
wraps Config::exact and reads SMARM_ALLOC_INTERVAL / SMARM_TIMESLICE_CYCLES
env vars, so the sweep script can vary knobs without recompiling.
Sweep tooling (benches/sweep.py):
- 'run': run the 3-file bench suite once; --save-baseline persists JSON
- 'regress': compare current run against baseline.json, exit 1 on any bench
that regresses >10% vs stored medians
- 'sweep': run the full SWEEP_GRID (10 points), print comparison table,
optional --save-csv; binaries pre-built so no recompile per point
Sweep results (10-point grid, 1-CPU sandbox):
- The preemption knobs have very little effect on this single-CPU machine.
Most benches move <5% across the entire grid.
- Longer timeslices (tc=600k, tc=1200k) reliably hurt spawn_storm_busy
(+11-15%) and catch_unwind_panics (+10-12%) because actors hold the
scheduler mutex longer per timeslice, stalling the storm of joinable tasks.
- Shorter timeslices (tc=150k) give a small improvement on many_timers
(-3-4%) and a wash everywhere else.
- yield_in_hot_loop and uncontended_channel are essentially flat across all
knobs — both are scheduling-dominated and call yield_now explicitly, so
the RDTSC-driven preemption path is irrelevant.
- Conclusion: the knobs matter primarily under contention (multi-core).
Re-run sweep on a multi-core machine before drawing tuning conclusions.
This commit is contained in:
Bench
442
benches/general.rs
Normal file
442
benches/general.rs
Normal file
@@ -0,0 +1,442 @@
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//! General benchmarks — workloads where neither runtime has a structural
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//! advantage. Both should be competitive; large gaps here indicate a real
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//! difference in per-task or per-yield overhead.
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//!
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//! Workloads:
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//! 1. chained_spawn — task N spawns N+1, depth 1000. Spawn+exit overhead in
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//! a serial chain. Adapted from tokio's bench of the same
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//! name.
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//! 2. yield_many — 200 actors × 1000 yields. Pure scheduling throughput
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//! with no allocation, no IO. Adapted from tokio.
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//! 3. fan_out_compute— count primes in [2, 400_000) across 64 workers. Same
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//! shape as multi_scheduler::primes but lives here for
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//! completeness.
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//! 4. ping_pong_oneshot — N rounds of (spawn pair, send oneshot, await).
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//! Closer to a request/response workload than channel
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//! ping-pong.
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use std::sync::atomic::{AtomicU64, Ordering};
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use std::sync::Arc;
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use std::time::Instant;
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// ---------------------------------------------------------------------------
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// Shared harness
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// ---------------------------------------------------------------------------
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const ITERS: u32 = 15;
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fn available_threads() -> usize {
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std::thread::available_parallelism().map(|n| n.get()).unwrap_or(1)
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}
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fn print_header(title: &str) {
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println!("\n{}", "=".repeat(80));
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println!(" {title}");
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println!("{}", "=".repeat(80));
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println!(
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"{:>26} | {:>12} | {:>10} | {:>10} | {:>10}",
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"runtime", "result", "median µs", "min µs", "max µs"
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);
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println!("{}", "-".repeat(80));
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}
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fn run_n<F: FnMut() -> (u64, u128)>(name: &str, n: u32, mut f: F) {
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let mut times = Vec::new();
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let mut last = 0u64;
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// One warmup iteration, discarded.
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let _ = f();
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for _ in 0..n {
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let (v, t) = f();
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times.push(t);
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last = v;
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}
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times.sort_unstable();
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let median = times[times.len() / 2];
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let min = *times.iter().min().unwrap();
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let max = *times.iter().max().unwrap();
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println!(
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"{:>26} | {:>12} | {:>10} | {:>10} | {:>10}",
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name, last, median, min, max
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);
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}
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// ---------------------------------------------------------------------------
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// 1. chained_spawn — depth 1000
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// ---------------------------------------------------------------------------
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const CHAIN_DEPTH: u64 = 1_000;
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fn bench_chained_smarm(threads: usize) -> (u64, u128) {
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let counter = Arc::new(AtomicU64::new(0));
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let c2 = counter.clone();
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let start = Instant::now();
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smarm::runtime::init(bench_cfg(threads)).run(move || {
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// Fire-and-forget chain, matching tokio's bench shape: each link
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// spawns the next link and exits immediately; depth 0 signals done
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// via a channel. Crucially this does *not* nest joins on the
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// spawner's stack — important because smarm actor stacks are a
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// fixed 64 KiB.
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let (tx, rx) = smarm::channel::<()>();
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fn iter(c: Arc<AtomicU64>, tx: smarm::Sender<()>, n: u64) {
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if n == 0 {
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tx.send(()).unwrap();
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} else {
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let cc = c.clone();
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smarm::spawn(move || {
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cc.fetch_add(1, Ordering::Relaxed);
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iter(cc.clone(), tx, n - 1);
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});
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// Caller exits; JoinHandle dropped, no parking.
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}
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}
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iter(c2, tx, CHAIN_DEPTH);
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rx.recv().unwrap();
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});
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(counter.load(Ordering::Relaxed), start.elapsed().as_micros())
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}
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fn bench_chained_tokio_current() -> (u64, u128) {
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let counter = Arc::new(AtomicU64::new(0));
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let c2 = counter.clone();
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let rt = tokio::runtime::Builder::new_current_thread().build().unwrap();
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let start = Instant::now();
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let local = tokio::task::LocalSet::new();
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local.block_on(&rt, async move {
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// Use a oneshot done channel like tokio's own chained_spawn bench.
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let (done_tx, done_rx) = tokio::sync::oneshot::channel();
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fn iter(
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c: Arc<AtomicU64>,
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done: tokio::sync::oneshot::Sender<()>,
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n: u64,
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) {
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if n == 0 {
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let _ = done.send(());
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} else {
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tokio::task::spawn_local(async move {
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c.fetch_add(1, Ordering::Relaxed);
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iter(c, done, n - 1);
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});
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}
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}
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iter(c2, done_tx, CHAIN_DEPTH);
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let _ = done_rx.await;
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});
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(counter.load(Ordering::Relaxed), start.elapsed().as_micros())
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}
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fn bench_chained_tokio_multi() -> (u64, u128) {
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let counter = Arc::new(AtomicU64::new(0));
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let c2 = counter.clone();
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let rt = tokio::runtime::Builder::new_multi_thread()
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.worker_threads(available_threads())
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.build()
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.unwrap();
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let start = Instant::now();
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rt.block_on(async move {
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let (done_tx, done_rx) = tokio::sync::oneshot::channel();
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fn iter(c: Arc<AtomicU64>, done: tokio::sync::oneshot::Sender<()>, n: u64) {
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if n == 0 {
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let _ = done.send(());
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} else {
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tokio::spawn(async move {
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c.fetch_add(1, Ordering::Relaxed);
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iter(c, done, n - 1);
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});
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}
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}
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iter(c2, done_tx, CHAIN_DEPTH);
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let _ = done_rx.await;
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});
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(counter.load(Ordering::Relaxed), start.elapsed().as_micros())
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}
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// ---------------------------------------------------------------------------
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// 2. yield_many — 200 actors × 1000 yields
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// ---------------------------------------------------------------------------
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const YIELD_TASKS: u64 = 200;
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const YIELD_ROUNDS: u64 = 1_000;
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fn bench_yield_smarm(threads: usize) -> (u64, u128) {
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let start = Instant::now();
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smarm::runtime::init(bench_cfg(threads)).run(|| {
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let mut handles = Vec::new();
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for _ in 0..YIELD_TASKS {
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handles.push(smarm::spawn(|| {
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for _ in 0..YIELD_ROUNDS {
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smarm::yield_now();
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}
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}));
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}
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for h in handles {
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h.join().unwrap();
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}
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});
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(YIELD_TASKS * YIELD_ROUNDS, start.elapsed().as_micros())
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}
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fn bench_yield_tokio_current() -> (u64, u128) {
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let rt = tokio::runtime::Builder::new_current_thread().build().unwrap();
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let start = Instant::now();
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let local = tokio::task::LocalSet::new();
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local.block_on(&rt, async move {
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let mut handles = Vec::new();
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for _ in 0..YIELD_TASKS {
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handles.push(tokio::task::spawn_local(async move {
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for _ in 0..YIELD_ROUNDS {
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tokio::task::yield_now().await;
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}
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}));
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}
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for h in handles {
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let _ = h.await;
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}
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});
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(YIELD_TASKS * YIELD_ROUNDS, start.elapsed().as_micros())
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}
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fn bench_yield_tokio_multi() -> (u64, u128) {
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let rt = tokio::runtime::Builder::new_multi_thread()
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.worker_threads(available_threads())
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.build()
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.unwrap();
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let start = Instant::now();
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rt.block_on(async move {
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let mut handles = Vec::new();
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for _ in 0..YIELD_TASKS {
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handles.push(tokio::spawn(async move {
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for _ in 0..YIELD_ROUNDS {
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tokio::task::yield_now().await;
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}
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}));
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}
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for h in handles {
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let _ = h.await;
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}
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});
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(YIELD_TASKS * YIELD_ROUNDS, start.elapsed().as_micros())
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}
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// ---------------------------------------------------------------------------
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// 3. fan_out_compute — primes, same shape as multi_scheduler::primes
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// ---------------------------------------------------------------------------
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const PRIME_N: u64 = 400_000;
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const PRIME_WORKERS: u64 = 64;
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fn is_prime(n: u64) -> bool {
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if n < 2 { return false; }
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if n < 4 { return true; }
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if n % 2 == 0 { return false; }
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let mut i = 3u64;
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while i * i <= n { if n % i == 0 { return false; } i += 2; }
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true
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}
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fn count_primes(lo: u64, hi: u64) -> u64 {
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(lo..hi).filter(|&n| is_prime(n)).count() as u64
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}
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fn primes_slice(w: u64) -> (u64, u64) {
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let per = PRIME_N / PRIME_WORKERS;
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let lo = w * per;
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let hi = if w + 1 == PRIME_WORKERS { PRIME_N } else { lo + per };
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(lo, hi)
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}
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fn bench_primes_smarm(threads: usize) -> (u64, u128) {
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let total = Arc::new(AtomicU64::new(0));
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let t2 = total.clone();
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let start = Instant::now();
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smarm::runtime::init(bench_cfg(threads)).run(move || {
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let mut handles = Vec::new();
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for w in 0..PRIME_WORKERS {
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let (lo, hi) = primes_slice(w);
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let tc = t2.clone();
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handles.push(smarm::spawn(move || {
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tc.fetch_add(count_primes(lo, hi), Ordering::Relaxed);
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}));
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}
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for h in handles { h.join().unwrap(); }
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});
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(total.load(Ordering::Relaxed), start.elapsed().as_micros())
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}
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fn bench_primes_tokio_current() -> (u64, u128) {
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let total = Arc::new(AtomicU64::new(0));
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let t2 = total.clone();
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let rt = tokio::runtime::Builder::new_current_thread().build().unwrap();
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let start = Instant::now();
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let local = tokio::task::LocalSet::new();
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local.block_on(&rt, async move {
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let mut handles = Vec::new();
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for w in 0..PRIME_WORKERS {
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let (lo, hi) = primes_slice(w);
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let tc = t2.clone();
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handles.push(tokio::task::spawn_local(async move {
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tc.fetch_add(count_primes(lo, hi), Ordering::Relaxed);
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}));
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}
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for h in handles { let _ = h.await; }
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});
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(total.load(Ordering::Relaxed), start.elapsed().as_micros())
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}
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fn bench_primes_tokio_multi() -> (u64, u128) {
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let total = Arc::new(AtomicU64::new(0));
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let t2 = total.clone();
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let rt = tokio::runtime::Builder::new_multi_thread()
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.worker_threads(available_threads())
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.build()
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.unwrap();
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let start = Instant::now();
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rt.block_on(async move {
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let mut handles = Vec::new();
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for w in 0..PRIME_WORKERS {
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let (lo, hi) = primes_slice(w);
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let tc = t2.clone();
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handles.push(tokio::spawn(async move {
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tc.fetch_add(count_primes(lo, hi), Ordering::Relaxed);
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}));
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}
|
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for h in handles { let _ = h.await; }
|
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});
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(total.load(Ordering::Relaxed), start.elapsed().as_micros())
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}
|
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|
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// ---------------------------------------------------------------------------
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// 4. ping_pong_oneshot — 1000 rounds of spawn-pair-await
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// ---------------------------------------------------------------------------
|
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|
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const PP_ROUNDS: u64 = 1_000;
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|
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fn bench_pp_smarm(threads: usize) -> (u64, u128) {
|
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let start = Instant::now();
|
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smarm::runtime::init(bench_cfg(threads)).run(|| {
|
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for _ in 0..PP_ROUNDS {
|
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// smarm has no oneshot, so use a channel<()> per round — both
|
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// sides spawn, A sends ping, B replies pong, A joins B.
|
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let (tx_ping, rx_ping) = smarm::channel::<()>();
|
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let (tx_pong, rx_pong) = smarm::channel::<()>();
|
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let hb = smarm::spawn(move || {
|
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rx_ping.recv().unwrap();
|
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tx_pong.send(()).unwrap();
|
||||
});
|
||||
let ha = smarm::spawn(move || {
|
||||
tx_ping.send(()).unwrap();
|
||||
rx_pong.recv().unwrap();
|
||||
});
|
||||
ha.join().unwrap();
|
||||
hb.join().unwrap();
|
||||
}
|
||||
});
|
||||
(PP_ROUNDS, start.elapsed().as_micros())
|
||||
}
|
||||
|
||||
fn bench_pp_tokio_current() -> (u64, u128) {
|
||||
let rt = tokio::runtime::Builder::new_current_thread().build().unwrap();
|
||||
let start = Instant::now();
|
||||
let local = tokio::task::LocalSet::new();
|
||||
local.block_on(&rt, async move {
|
||||
for _ in 0..PP_ROUNDS {
|
||||
let (tx1, rx1) = tokio::sync::oneshot::channel::<()>();
|
||||
let (tx2, rx2) = tokio::sync::oneshot::channel::<()>();
|
||||
let hb = tokio::task::spawn_local(async move {
|
||||
rx1.await.unwrap();
|
||||
tx2.send(()).unwrap();
|
||||
});
|
||||
let ha = tokio::task::spawn_local(async move {
|
||||
tx1.send(()).unwrap();
|
||||
rx2.await.unwrap();
|
||||
});
|
||||
let _ = ha.await;
|
||||
let _ = hb.await;
|
||||
}
|
||||
});
|
||||
(PP_ROUNDS, start.elapsed().as_micros())
|
||||
}
|
||||
|
||||
fn bench_pp_tokio_multi() -> (u64, u128) {
|
||||
let rt = tokio::runtime::Builder::new_multi_thread()
|
||||
.worker_threads(available_threads())
|
||||
.build()
|
||||
.unwrap();
|
||||
let start = Instant::now();
|
||||
rt.block_on(async move {
|
||||
for _ in 0..PP_ROUNDS {
|
||||
let (tx1, rx1) = tokio::sync::oneshot::channel::<()>();
|
||||
let (tx2, rx2) = tokio::sync::oneshot::channel::<()>();
|
||||
let hb = tokio::spawn(async move {
|
||||
rx1.await.unwrap();
|
||||
tx2.send(()).unwrap();
|
||||
});
|
||||
let ha = tokio::spawn(async move {
|
||||
tx1.send(()).unwrap();
|
||||
rx2.await.unwrap();
|
||||
});
|
||||
let _ = ha.await;
|
||||
let _ = hb.await;
|
||||
}
|
||||
});
|
||||
(PP_ROUNDS, start.elapsed().as_micros())
|
||||
}
|
||||
|
||||
// ---------------------------------------------------------------------------
|
||||
// main
|
||||
// ---------------------------------------------------------------------------
|
||||
|
||||
|
||||
// ---------------------------------------------------------------------------
|
||||
// Knob helper — reads SMARM_ALLOC_INTERVAL / SMARM_TIMESLICE_CYCLES env vars
|
||||
// so the sweep script can override the preemption knobs without recompiling.
|
||||
// ---------------------------------------------------------------------------
|
||||
|
||||
fn bench_cfg(threads: usize) -> smarm::runtime::Config {
|
||||
let mut cfg = smarm::runtime::Config::exact(threads);
|
||||
if let Ok(v) = std::env::var("SMARM_ALLOC_INTERVAL") {
|
||||
if let Ok(n) = v.parse::<u32>() { cfg = cfg.alloc_interval(n); }
|
||||
}
|
||||
if let Ok(v) = std::env::var("SMARM_TIMESLICE_CYCLES") {
|
||||
if let Ok(n) = v.parse::<u64>() { cfg = cfg.timeslice_cycles(n); }
|
||||
}
|
||||
cfg
|
||||
}
|
||||
|
||||
fn main() {
|
||||
let n = available_threads();
|
||||
println!("smarm general benchmarks");
|
||||
println!("available parallelism: {n} threads");
|
||||
println!("ITERS={ITERS} (+1 warmup, discarded)");
|
||||
println!(
|
||||
"CHAIN_DEPTH={CHAIN_DEPTH}, YIELD_TASKS={YIELD_TASKS}×{YIELD_ROUNDS}, \
|
||||
PRIME_N={PRIME_N}/{PRIME_WORKERS} workers, PP_ROUNDS={PP_ROUNDS}"
|
||||
);
|
||||
|
||||
// ---- 1. chained_spawn ----
|
||||
print_header(&format!("chained_spawn: depth {CHAIN_DEPTH}"));
|
||||
run_n("smarm 1-thread", ITERS, || bench_chained_smarm(1));
|
||||
run_n(&format!("smarm {n}-thread"), ITERS, || bench_chained_smarm(n));
|
||||
run_n("tokio current_thread", ITERS, bench_chained_tokio_current);
|
||||
run_n("tokio multi-thread", ITERS, bench_chained_tokio_multi);
|
||||
|
||||
// ---- 2. yield_many ----
|
||||
print_header(&format!("yield_many: {YIELD_TASKS} tasks × {YIELD_ROUNDS} yields"));
|
||||
run_n("smarm 1-thread", ITERS, || bench_yield_smarm(1));
|
||||
run_n(&format!("smarm {n}-thread"), ITERS, || bench_yield_smarm(n));
|
||||
run_n("tokio current_thread", ITERS, bench_yield_tokio_current);
|
||||
run_n("tokio multi-thread", ITERS, bench_yield_tokio_multi);
|
||||
|
||||
// ---- 3. fan_out_compute ----
|
||||
print_header(&format!("fan_out_compute: primes in [2, {PRIME_N}) across {PRIME_WORKERS}"));
|
||||
run_n("smarm 1-thread", ITERS, || bench_primes_smarm(1));
|
||||
run_n(&format!("smarm {n}-thread"), ITERS, || bench_primes_smarm(n));
|
||||
run_n("tokio current_thread", ITERS, bench_primes_tokio_current);
|
||||
run_n("tokio multi-thread", ITERS, bench_primes_tokio_multi);
|
||||
|
||||
// ---- 4. ping_pong_oneshot ----
|
||||
print_header(&format!("ping_pong_oneshot: {PP_ROUNDS} rounds"));
|
||||
run_n("smarm 1-thread", ITERS, || bench_pp_smarm(1));
|
||||
run_n(&format!("smarm {n}-thread"), ITERS, || bench_pp_smarm(n));
|
||||
run_n("tokio current_thread", ITERS, bench_pp_tokio_current);
|
||||
run_n("tokio multi-thread", ITERS, bench_pp_tokio_multi);
|
||||
}
|
||||
Reference in New Issue
Block a user