enhance(dev): tweak get-backend-memory

.github/scripts/memory-stability-util.mts

@@ -0,0 +1,75 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { setTimeout } from 'node:timers/promises';
+
+type MemoryStabilityTimer = {
+	now: () => number;
+	wait: (durationMs: number) => Promise<void>;
+};
+
+const intervalMs = 2000;
+const maxWaitMs = 10000;
+const windowSize = 3;
+const slopeThresholdKiBPerSecond = 256;
+const stabilityMetrics = ['Pss', 'Private_Dirty'] as const;
+
+const defaultTimer: MemoryStabilityTimer = {
+	now: () => performance.now(),
+	wait: durationMs => setTimeout(durationMs),
+};
+
+function getMaxAbsoluteSlopes<T extends Record<string, number>>(readings: { elapsedMs: number; memoryUsage: T }[]) {
+	const result = {} as Record<typeof stabilityMetrics[number], number>;
+
+	for (const metric of stabilityMetrics) {
+		let maxAbsoluteSlope = 0;
+		for (let i = 1; i < readings.length; i++) {
+			const previous = readings[i - 1];
+			const current = readings[i];
+			const durationSeconds = (current.elapsedMs - previous.elapsedMs) / 1000;
+			maxAbsoluteSlope = Math.max(maxAbsoluteSlope, Math.abs(current.memoryUsage[metric] - previous.memoryUsage[metric]) / durationSeconds);
+		}
+		result[metric] = maxAbsoluteSlope;
+	}
+
+	return result;
+}
+
+export async function measureMemoryUntilStable<T extends Record<string, number>>(
+	readMemoryUsage: () => Promise<T>,
+	timer: MemoryStabilityTimer = defaultTimer,
+) {
+	const startedAt = timer.now();
+	const readings: { elapsedMs: number; memoryUsage: T }[] = [];
+	let maxAbsoluteSlopesKiBPerSecond: Record<typeof stabilityMetrics[number], number> | null = null;
+
+	while (true) {
+		const memoryUsage = await readMemoryUsage();
+		const elapsedMs = timer.now() - startedAt;
+		readings.push({ elapsedMs, memoryUsage });
+
+		let converged = false;
+		if (readings.length >= windowSize) {
+			const latestSlopes = getMaxAbsoluteSlopes(readings.slice(-windowSize));
+			maxAbsoluteSlopesKiBPerSecond = latestSlopes;
+			converged = stabilityMetrics.every(metric => latestSlopes[metric] <= slopeThresholdKiBPerSecond);
+		}
+
+		if (converged || elapsedMs >= maxWaitMs) {
+			return {
+				memoryUsage,
+				stability: {
+					converged,
+					readingCount: readings.length,
+					elapsedMs,
+					maxAbsoluteSlopesKiBPerSecond,
+				},
+			};
+		}
+
+		await timer.wait(Math.min(intervalMs, maxWaitMs - elapsedMs));
+	}
+}