perf(net): sample send-rate estimates from one page-wide ticker

js/net/src/connection/reload.ts

@@ -20,6 +20,7 @@ import type { Established } from "./established.ts";
 import { DISCOVERY_REMOVED } from "./forward.ts";
 import { DEFAULT_HANDOVER, type Drain, dialed, type GoawayProps, handover, pinnedTransport, target } from "./goaway.ts";
 import { estimates, type Probe } from "./stats.ts";
+import { tick } from "./ticker.ts";
 import { heldOf } from "./tokens.ts";
 
 function sameTokens(a: readonly string[], b: readonly string[]): boolean {
@@ -454,7 +455,8 @@ export class Reload {
 			};
 
 			void sample();
-			effect.interval(() => void sample(), BANDWIDTH_POLL);
+			// One page-wide ticker samples every connection in the same wakeup.
+			effect.cleanup(tick(BANDWIDTH_POLL, () => void sample()));
 		});
 
 		// The live session holds the current tokens on AUTH; a dial picks them up itself.

js/net/src/connection/ticker.test.ts

@@ -0,0 +1,34 @@
+import { expect, test } from "bun:test";
+import { Manual, Milli, Nano } from "@moq/clock";
+import { tick } from "./ticker.ts";
+
+test("subscribers share one tick and the loop stops with the last", async () => {
+	const clock = new Manual();
+	const installed = clock.install();
+	try {
+		const period = Nano.fromMilli(Milli(100));
+		const ticks: string[] = [];
+		const a = tick(period, () => ticks.push("a"));
+		await clock.advance(Nano.fromMilli(Milli(50)));
+		// Joins the running loop rather than starting its own out of phase.
+		const b = tick(period, () => ticks.push("b"));
+		await clock.advance(Nano.fromMilli(Milli(50)));
+		expect(ticks).toEqual(["a", "b"]);
+
+		a();
+		await clock.advance(period);
+		expect(ticks).toEqual(["a", "b", "b"]);
+
+		b();
+		b();
+		await clock.advance(Nano.fromMilli(Milli(500)));
+		expect(ticks).toEqual(["a", "b", "b"]);
+
+		// A stopped loop restarts for a later subscriber, rather than leaving the page unsampled.
+		tick(period, () => ticks.push("c"));
+		await clock.advance(period);
+		expect(ticks).toEqual(["a", "b", "b", "c"]);
+	} finally {
+		installed.close();
+	}
+});

js/net/src/connection/ticker.ts

@@ -0,0 +1,65 @@
+import { Instant, type Nano, now, sleepUntil } from "@moq/clock";
+
+/**
+ * One page-wide ticker shared by every caller with the same period.
+ *
+ * Each subscriber's callback runs once per tick, all in the same task, so N
+ * connections sampling `getStats()` cost one timer wakeup per period instead of N
+ * loops ticking out of phase. The loop runs only while a subscriber is registered.
+ */
+class Ticker {
+	readonly #period: Nano;
+	readonly #subscribers = new Set<() => void>();
+	#abort?: AbortController;
+
+	constructor(period: Nano) {
+		this.#period = period;
+	}
+
+	/** Runs `fn` on every tick until the returned dispose is called. */
+	subscribe(fn: () => void): () => void {
+		this.#subscribers.add(fn);
+		if (!this.#abort) this.#start();
+		return () => {
+			if (!this.#subscribers.delete(fn)) return;
+			if (this.#subscribers.size === 0) {
+				this.#abort?.abort();
+				this.#abort = undefined;
+			}
+		};
+	}
+
+	#start() {
+		const abort = new AbortController();
+		this.#abort = abort;
+		void (async () => {
+			let next = Instant.add(now(), this.#period);
+			for (;;) {
+				await sleepUntil(next, { signal: abort.signal }).catch(() => {});
+				if (abort.signal.aborted) return;
+				// Snapshot so a callback that unsubscribes doesn't skip a neighbour.
+				for (const fn of [...this.#subscribers]) {
+					try {
+						fn();
+					} catch (err) {
+						console.error("ticker callback error", err);
+					}
+				}
+				next = Instant.add(now(), this.#period);
+			}
+		})();
+	}
+}
+
+const tickers = new Map<Nano, Ticker>();
+
+/** Subscribes `fn` to the page-wide ticker for `period`; returns its dispose. */
+export function tick(period: Nano, fn: () => void): () => void {
+	if (period <= 0) throw new RangeError("ticker period must be positive");
+	let ticker = tickers.get(period);
+	if (!ticker) {
+		ticker = new Ticker(period);
+		tickers.set(period, ticker);
+	}
+	return ticker.subscribe(fn);
+}

quest/m2/probe/README.md

@@ -100,7 +100,6 @@ This README's own work, once the children land:
 ## Required
 
 - [Browser send estimate](/quest/m2/probe/browser-send-estimate.md) - browser publishers adapt to `getStats()`'s send estimate once Chrome and Safari report one
-- [One page-wide getStats sampling ticker](/quest/m2/probe/stats-ticker.md) - a page's connections share one sampling ticker
 
 ## Related
 

quest/m2/probe/browser-send-estimate.md

@@ -44,6 +44,5 @@ Public API: none expected. Wire: none.
 
 ## Related
 
-- [One page-wide getStats sampling ticker](/quest/m2/probe/stats-ticker.md) - shares the `getStats()` sampling this reads
 - [Padding probes](/quest/m3/probe-padding.md) - raises the estimate once one exists
 - [Media stats](/quest/m3/stats/README.md) - its JS stats read PROBE for the downlink

quest/m2/recut-held.md

@@ -31,4 +31,3 @@ padding probes already moved to m3 on 2026-11-06.
 
 - [Release on leave](/quest/m1/stream-credit/release-on-leave.md) - claim held stream-credit
 - [Browser send estimate](/quest/m2/probe/browser-send-estimate.md) - claim held probe
-- [One page-wide getStats sampling ticker](/quest/m2/probe/stats-ticker.md) - claim held probe