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/**
* Lightweight rolling perf instrumentation for the render pipeline.
*
* Toggle at runtime from the devtools console:
* window.__renderPerf = true
*
* Every FLUSH_EVERY frames the aggregator dumps:
* - per-span timing summary (count / mean / p50 / p95 / max, in ms)
* - per-counter totals (uploads, canvas allocations by kind, etc.)
*
* Zero overhead when disabled: `isRenderPerfEnabled()` short-circuits before
* any recording happens, so call sites only pay for a global read.
*/
type SpanSample = number;
type SpanStats = {
samples: SpanSample[];
};
type CounterStats = {
total: number;
frames: number;
};
const FLUSH_EVERY = 60;
const spans = new Map<string, SpanStats>();
const counters = new Map<string, CounterStats>();
const pendingCountersThisFrame = new Map<string, number>();
let framesSinceFlush = 0;
declare global {
interface Window {
__renderPerf?: boolean;
}
}
export function isRenderPerfEnabled(): boolean {
return typeof window !== "undefined" && window.__renderPerf === true;
}
export function recordSpan({
name,
durationMs,
}: {
name: string;
durationMs: number;
}): void {
if (!isRenderPerfEnabled()) return;
let stats = spans.get(name);
if (!stats) {
stats = { samples: [] };
spans.set(name, stats);
}
stats.samples.push(durationMs);
}
export async function measureSpanAsync<T>({
name,
fn,
}: {
name: string;
fn: () => Promise<T>;
}): Promise<T> {
if (!isRenderPerfEnabled()) return fn();
const start = performance.now();
try {
return await fn();
} finally {
recordSpan({ name, durationMs: performance.now() - start });
}
}
export function measureSpanSync<T>({
name,
fn,
}: {
name: string;
fn: () => T;
}): T {
if (!isRenderPerfEnabled()) return fn();
const start = performance.now();
try {
return fn();
} finally {
recordSpan({ name, durationMs: performance.now() - start });
}
}
export function incrementCounter({
name,
by = 1,
}: {
name: string;
by?: number;
}): void {
if (!isRenderPerfEnabled()) return;
pendingCountersThisFrame.set(
name,
(pendingCountersThisFrame.get(name) ?? 0) + by,
);
}
/**
* Pulls sub-span timings recorded inside the wasm `renderFrame` call and
* feeds them into the aggregator as ordinary spans.
*/
export function recordWasmFrameProfile(
entries: Array<{ name: string; durationMs: number }>,
): void {
if (!isRenderPerfEnabled()) return;
for (const entry of entries) {
recordSpan({ name: entry.name, durationMs: entry.durationMs });
}
}
/**
* Called once per frame by the top of the render pipeline. Rolls the
* pending-frame counters into the aggregate and triggers a flush on cadence.
*/
export function onRenderPerfFrameComplete(): void {
if (!isRenderPerfEnabled()) return;
for (const [name, count] of pendingCountersThisFrame) {
let stats = counters.get(name);
if (!stats) {
stats = { total: 0, frames: 0 };
counters.set(name, stats);
}
stats.total += count;
stats.frames += 1;
}
pendingCountersThisFrame.clear();
framesSinceFlush += 1;
if (framesSinceFlush >= FLUSH_EVERY) {
flush();
}
}
function flush(): void {
const spanRows: Array<Record<string, number | string>> = [];
for (const [name, stats] of spans) {
if (stats.samples.length === 0) continue;
const sorted = [...stats.samples].sort((a, b) => a - b);
const p = (q: number) =>
sorted[Math.min(sorted.length - 1, Math.floor(sorted.length * q))];
const sum = sorted.reduce((acc, v) => acc + v, 0);
spanRows.push({
span: name,
count: sorted.length,
meanMs: +(sum / sorted.length).toFixed(2),
p50Ms: +p(0.5).toFixed(2),
p95Ms: +p(0.95).toFixed(2),
maxMs: +sorted[sorted.length - 1].toFixed(2),
});
}
spanRows.sort((a, b) => Number(b.meanMs) - Number(a.meanMs));
const counterRows: Array<Record<string, number | string>> = [];
for (const [name, stats] of counters) {
counterRows.push({
counter: name,
perFrame: +(stats.total / Math.max(1, stats.frames)).toFixed(2),
total: stats.total,
frames: stats.frames,
});
}
counterRows.sort((a, b) => Number(b.perFrame) - Number(a.perFrame));
console.groupCollapsed(
`[render-perf] summary over ${framesSinceFlush} frames`,
);
if (spanRows.length > 0) console.table(spanRows);
if (counterRows.length > 0) console.table(counterRows);
console.groupEnd();
spans.clear();
counters.clear();
framesSinceFlush = 0;
}
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