648 lines
28 KiB
JavaScript
648 lines
28 KiB
JavaScript
/**
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* Line Profiler Experiment
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*
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* Compares different approaches to line-level profiling in Node.js:
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* 1. V8 Inspector sampling profiler
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* 2. Custom instrumentation with process.hrtime.bigint()
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* 3. Manual instrumentation (most accurate baseline)
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*
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* Evaluates:
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* - Accuracy of timing measurements
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* - Overhead introduced by profiling
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* - Granularity of line-level data
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* - JIT warmup effects
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*/
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const {
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fibonacci,
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reverseString,
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bubbleSort,
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countWords,
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matrixMultiply,
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classifyNumber
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} = require('./target-functions');
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const customProfiler = require('./custom-line-profiler');
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const v8Profiler = require('./v8-inspector-profiler');
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// ============================================================================
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// Experiment Configuration
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// ============================================================================
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const WARMUP_ITERATIONS = 1000;
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const MEASUREMENT_ITERATIONS = 10000;
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const RESULTS = {};
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// ============================================================================
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// Utility Functions
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// ============================================================================
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function formatNs(ns) {
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if (ns < 1000) return `${ns.toFixed(0)}ns`;
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if (ns < 1000000) return `${(ns / 1000).toFixed(2)}μs`;
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if (ns < 1000000000) return `${(ns / 1000000).toFixed(2)}ms`;
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return `${(ns / 1000000000).toFixed(2)}s`;
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}
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function formatPercent(value, total) {
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return ((value / total) * 100).toFixed(1) + '%';
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}
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/**
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* Measure baseline execution time without profiling.
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*/
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function measureBaseline(func, args, iterations) {
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// Warmup
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for (let i = 0; i < WARMUP_ITERATIONS; i++) {
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func(...args);
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}
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// Measure
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const start = process.hrtime.bigint();
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for (let i = 0; i < iterations; i++) {
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func(...args);
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}
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const end = process.hrtime.bigint();
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return Number(end - start) / iterations;
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}
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/**
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* Measure execution time with custom instrumentation.
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*/
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function measureInstrumented(func, args, iterations) {
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customProfiler.clearTimings();
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// Warmup
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for (let i = 0; i < WARMUP_ITERATIONS; i++) {
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func(...args);
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}
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customProfiler.clearTimings();
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// Measure
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const start = process.hrtime.bigint();
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for (let i = 0; i < iterations; i++) {
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func(...args);
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}
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const end = process.hrtime.bigint();
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return {
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avgTimeNs: Number(end - start) / iterations,
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timings: customProfiler.getTimings()
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};
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}
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// ============================================================================
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// Experiment 1: V8 Inspector Sampling Profiler
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// ============================================================================
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async function experimentV8Profiler() {
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console.log('\n' + '='.repeat(70));
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console.log('EXPERIMENT 1: V8 Inspector Sampling Profiler');
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console.log('='.repeat(70));
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console.log('Uses V8\'s built-in sampling profiler via the inspector protocol.');
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console.log('Advantage: Low overhead, no code modification required.');
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console.log('Disadvantage: Sampling-based, may miss short-lived operations.\n');
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try {
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// Start profiling
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await v8Profiler.startPreciseProfiling();
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// Warmup
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console.log('Warming up...');
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for (let i = 0; i < WARMUP_ITERATIONS; i++) {
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fibonacci(30);
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reverseString('hello world '.repeat(100));
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bubbleSort([5, 3, 8, 1, 9, 2, 7, 4, 6]);
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}
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// Run measurements
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console.log('Running measurements...');
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const iterations = 5000;
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for (let i = 0; i < iterations; i++) {
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fibonacci(30);
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reverseString('hello world '.repeat(100));
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bubbleSort([5, 3, 8, 1, 9, 2, 7, 4, 6]);
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}
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// Stop and get results
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const { profile, coverage } = await v8Profiler.stopPreciseProfiling();
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v8Profiler.disconnect();
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// Parse and display results
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const lineTimings = v8Profiler.parseProfile(profile);
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console.log('\n--- V8 Profiler Results ---');
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console.log(`Total samples: ${profile.samples?.length || 0}`);
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console.log(`Sampling interval: ${profile.samplingInterval || 'unknown'}μs`);
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// Show top hotspots
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const allLines = [];
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for (const [filename, lines] of Object.entries(lineTimings)) {
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if (filename.includes('target-functions')) {
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for (const [line, data] of Object.entries(lines)) {
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allLines.push({ filename, line, ...data });
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}
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}
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}
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allLines.sort((a, b) => b.hits - a.hits);
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console.log('\nTop 10 hotspots:');
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for (const entry of allLines.slice(0, 10)) {
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console.log(` ${entry.functionName} line ${entry.line}: ${entry.hits} hits (${entry.percentage}%)`);
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}
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RESULTS.v8Profiler = {
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totalSamples: profile.samples?.length || 0,
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lineTimings,
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overhead: 'Low (sampling-based)',
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granularity: 'Function-level with approximate line info'
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};
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} catch (err) {
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console.error('V8 Profiler experiment failed:', err.message);
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RESULTS.v8Profiler = { error: err.message };
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}
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}
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// ============================================================================
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// Experiment 2: Custom hrtime.bigint() Instrumentation
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// ============================================================================
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async function experimentCustomInstrumentation() {
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console.log('\n' + '='.repeat(70));
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console.log('EXPERIMENT 2: Custom process.hrtime.bigint() Instrumentation');
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console.log('='.repeat(70));
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console.log('Inserts timing calls around each statement.');
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console.log('Advantage: Precise per-line timing.');
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console.log('Disadvantage: Significant overhead, requires code transformation.\n');
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// Test manually instrumented functions
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const instrumentedFib = customProfiler.createManuallyInstrumentedFibonacci();
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const instrumentedReverse = customProfiler.createManuallyInstrumentedReverseString();
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const instrumentedBubble = customProfiler.createManuallyInstrumentedBubbleSort();
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// Measure baseline
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console.log('Measuring baseline (uninstrumented)...');
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const baselineFib = measureBaseline(fibonacci, [30], MEASUREMENT_ITERATIONS);
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const baselineReverse = measureBaseline(reverseString, ['hello world '.repeat(100)], MEASUREMENT_ITERATIONS);
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const baselineBubble = measureBaseline(bubbleSort, [[5, 3, 8, 1, 9, 2, 7, 4, 6]], MEASUREMENT_ITERATIONS / 10);
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console.log(` fibonacci(30): ${formatNs(baselineFib)} per call`);
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console.log(` reverseString: ${formatNs(baselineReverse)} per call`);
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console.log(` bubbleSort: ${formatNs(baselineBubble)} per call`);
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// Measure instrumented
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console.log('\nMeasuring instrumented...');
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customProfiler.clearTimings();
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const instrFibResult = measureInstrumented(instrumentedFib, [30], MEASUREMENT_ITERATIONS);
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const instrReverseResult = measureInstrumented(instrumentedReverse, ['hello world '.repeat(100)], MEASUREMENT_ITERATIONS);
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const instrBubbleResult = measureInstrumented(instrumentedBubble, [[5, 3, 8, 1, 9, 2, 7, 4, 6]], MEASUREMENT_ITERATIONS / 10);
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console.log(` fibonacci(30): ${formatNs(instrFibResult.avgTimeNs)} per call`);
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console.log(` reverseString: ${formatNs(instrReverseResult.avgTimeNs)} per call`);
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console.log(` bubbleSort: ${formatNs(instrBubbleResult.avgTimeNs)} per call`);
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// Calculate overhead
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const overheadFib = ((instrFibResult.avgTimeNs - baselineFib) / baselineFib * 100).toFixed(1);
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const overheadReverse = ((instrReverseResult.avgTimeNs - baselineReverse) / baselineReverse * 100).toFixed(1);
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const overheadBubble = ((instrBubbleResult.avgTimeNs - baselineBubble) / baselineBubble * 100).toFixed(1);
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console.log('\n--- Overhead Analysis ---');
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console.log(` fibonacci: +${overheadFib}% overhead`);
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console.log(` reverseString: +${overheadReverse}% overhead`);
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console.log(` bubbleSort: +${overheadBubble}% overhead`);
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// Display line-level timings
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console.log('\n--- Line-Level Timings (from instrumented runs) ---');
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const allTimings = customProfiler.getTimings();
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for (const [funcName, lines] of Object.entries(allTimings)) {
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console.log(`\n${funcName}:`);
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const sortedLines = Object.entries(lines)
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.sort(([a], [b]) => parseInt(a) - parseInt(b));
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let totalTime = 0;
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for (const [line, data] of sortedLines) {
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totalTime += data.totalNs;
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}
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for (const [line, data] of sortedLines) {
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const pct = formatPercent(data.totalNs, totalTime);
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console.log(` Line ${line.padStart(2)}: ${data.count.toString().padStart(10)} calls, ` +
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`${formatNs(data.avgNs).padStart(10)} avg, ` +
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`${formatNs(data.totalNs).padStart(12)} total (${pct})`);
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}
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}
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RESULTS.customInstrumentation = {
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baselines: {
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fibonacci: baselineFib,
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reverseString: baselineReverse,
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bubbleSort: baselineBubble
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},
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instrumented: {
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fibonacci: instrFibResult.avgTimeNs,
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reverseString: instrReverseResult.avgTimeNs,
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bubbleSort: instrBubbleResult.avgTimeNs
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},
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overhead: {
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fibonacci: overheadFib + '%',
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reverseString: overheadReverse + '%',
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bubbleSort: overheadBubble + '%'
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},
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lineTimings: allTimings
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};
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}
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// ============================================================================
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// Experiment 3: Timing Accuracy Verification
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// ============================================================================
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async function experimentTimingAccuracy() {
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console.log('\n' + '='.repeat(70));
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console.log('EXPERIMENT 3: Timing Accuracy Verification');
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console.log('='.repeat(70));
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console.log('Verifies that hrtime.bigint() timings are consistent and accurate.\n');
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// Test 1: Timer overhead
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console.log('Test 1: Measuring timer overhead...');
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const timerOverheads = [];
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for (let i = 0; i < 10000; i++) {
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const start = process.hrtime.bigint();
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const end = process.hrtime.bigint();
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timerOverheads.push(Number(end - start));
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}
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const avgTimerOverhead = timerOverheads.reduce((a, b) => a + b, 0) / timerOverheads.length;
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const minTimerOverhead = Math.min(...timerOverheads);
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const maxTimerOverhead = Math.max(...timerOverheads);
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console.log(` Average timer overhead: ${formatNs(avgTimerOverhead)}`);
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console.log(` Min: ${formatNs(minTimerOverhead)}, Max: ${formatNs(maxTimerOverhead)}`);
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// Test 2: Consistency across runs
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console.log('\nTest 2: Timing consistency across runs...');
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const runs = [];
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for (let run = 0; run < 5; run++) {
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const start = process.hrtime.bigint();
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for (let i = 0; i < 100000; i++) {
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fibonacci(20);
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}
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const end = process.hrtime.bigint();
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runs.push(Number(end - start) / 100000);
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}
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const avgRun = runs.reduce((a, b) => a + b, 0) / runs.length;
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const variance = runs.reduce((sum, r) => sum + Math.pow(r - avgRun, 2), 0) / runs.length;
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const stdDev = Math.sqrt(variance);
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const coeffVar = (stdDev / avgRun * 100).toFixed(2);
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console.log(' Run times (ns per call): ' + runs.map(r => formatNs(r)).join(', '));
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console.log(` Average: ${formatNs(avgRun)}`);
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console.log(` Std Dev: ${formatNs(stdDev)}`);
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console.log(` Coefficient of Variation: ${coeffVar}%`);
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// Test 3: JIT warmup effect
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console.log('\nTest 3: JIT warmup effect...');
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// Create a fresh function to see JIT progression
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const freshFunc = new Function('n', `
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if (n <= 1) return n;
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let a = 0, b = 1;
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for (let i = 2; i <= n; i++) {
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const temp = a + b;
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a = b;
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b = temp;
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}
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return b;
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`);
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const jitTimings = [];
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for (let batch = 0; batch < 10; batch++) {
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const start = process.hrtime.bigint();
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for (let i = 0; i < 1000; i++) {
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freshFunc(30);
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}
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const end = process.hrtime.bigint();
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jitTimings.push(Number(end - start) / 1000);
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}
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console.log(' Batch timings (ns per call): ');
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for (let i = 0; i < jitTimings.length; i++) {
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const speedup = i > 0 ? ((jitTimings[0] - jitTimings[i]) / jitTimings[0] * 100).toFixed(1) : '0.0';
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console.log(` Batch ${i + 1}: ${formatNs(jitTimings[i])} (${speedup}% faster than first)`);
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}
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RESULTS.timingAccuracy = {
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timerOverhead: {
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avg: avgTimerOverhead,
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min: minTimerOverhead,
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max: maxTimerOverhead
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},
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consistency: {
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coefficientOfVariation: coeffVar + '%',
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runs
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},
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jitWarmup: jitTimings
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};
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}
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// ============================================================================
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// Experiment 4: Line Timing Relative Accuracy
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// ============================================================================
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async function experimentRelativeAccuracy() {
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console.log('\n' + '='.repeat(70));
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console.log('EXPERIMENT 4: Relative Line Timing Accuracy');
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console.log('='.repeat(70));
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console.log('Tests if line timings correctly identify hot spots.\n');
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// Create a function with known expensive and cheap lines
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const testFunc = function knownProfile(n) {
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// Line 1: Cheap - variable declaration
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let result = 0;
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// Line 2: Expensive - loop with computation
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for (let i = 0; i < n; i++) {
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// Line 3: Medium - string operation
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const str = i.toString();
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// Line 4: Cheap - simple arithmetic
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result += i;
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// Line 5: Expensive - array allocation
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const arr = new Array(100).fill(i);
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// Line 6: Cheap - property access
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const len = arr.length;
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}
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// Line 7: Return
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return result;
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};
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// Manually instrumented version
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const instrumentedTest = function knownProfile_instrumented(n) {
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let t;
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const timings = {};
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// Line 1: Cheap - variable declaration
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t = process.hrtime.bigint();
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let result = 0;
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customProfiler.recordLineTiming('knownProfile', 1, process.hrtime.bigint() - t);
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// Line 2: Loop
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t = process.hrtime.bigint();
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for (let i = 0; i < n; i++) {
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customProfiler.recordLineTiming('knownProfile', 2, process.hrtime.bigint() - t);
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// Line 3: String operation
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t = process.hrtime.bigint();
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const str = i.toString();
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customProfiler.recordLineTiming('knownProfile', 3, process.hrtime.bigint() - t);
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// Line 4: Simple arithmetic
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t = process.hrtime.bigint();
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result += i;
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customProfiler.recordLineTiming('knownProfile', 4, process.hrtime.bigint() - t);
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// Line 5: Array allocation
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t = process.hrtime.bigint();
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const arr = new Array(100).fill(i);
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customProfiler.recordLineTiming('knownProfile', 5, process.hrtime.bigint() - t);
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// Line 6: Property access
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t = process.hrtime.bigint();
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const len = arr.length;
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customProfiler.recordLineTiming('knownProfile', 6, process.hrtime.bigint() - t);
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t = process.hrtime.bigint();
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}
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customProfiler.recordLineTiming('knownProfile', 2, process.hrtime.bigint() - t);
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// Line 7: Return
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t = process.hrtime.bigint();
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const ret = result;
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customProfiler.recordLineTiming('knownProfile', 7, process.hrtime.bigint() - t);
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return ret;
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};
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// Warmup
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for (let i = 0; i < 1000; i++) {
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instrumentedTest(100);
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}
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// Measure
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customProfiler.clearTimings();
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for (let i = 0; i < 5000; i++) {
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instrumentedTest(100);
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}
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const timings = customProfiler.getTimings()['knownProfile'];
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console.log('Expected relative costs:');
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console.log(' Line 1 (var decl): Very cheap');
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console.log(' Line 2 (loop overhead): Cheap');
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console.log(' Line 3 (toString): Medium');
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console.log(' Line 4 (arithmetic): Very cheap');
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console.log(' Line 5 (array alloc): Expensive');
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console.log(' Line 6 (property): Very cheap');
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console.log(' Line 7 (return): Very cheap');
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console.log('\nActual measured costs:');
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let totalTime = 0;
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for (const data of Object.values(timings)) {
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totalTime += data.totalNs;
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}
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const sortedLines = Object.entries(timings)
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.sort(([, a], [, b]) => b.totalNs - a.totalNs);
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for (const [line, data] of sortedLines) {
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const pct = formatPercent(data.totalNs, totalTime);
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console.log(` Line ${line}: ${pct.padStart(6)} - ${formatNs(data.avgNs)} avg`);
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}
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// Verify expected ordering
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console.log('\nVerification:');
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const line5Time = timings[5]?.totalNs || 0; // Array allocation
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const line3Time = timings[3]?.totalNs || 0; // toString
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const line4Time = timings[4]?.totalNs || 0; // arithmetic
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const line5Dominant = line5Time > line3Time && line5Time > line4Time;
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const line3MoreThan4 = line3Time > line4Time;
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console.log(` Array allocation (line 5) is most expensive: ${line5Dominant ? 'YES ✓' : 'NO ✗'}`);
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console.log(` toString (line 3) more expensive than arithmetic (line 4): ${line3MoreThan4 ? 'YES ✓' : 'NO ✗'}`);
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RESULTS.relativeAccuracy = {
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timings,
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verification: {
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arrayMostExpensive: line5Dominant,
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toStringMoreThanArithmetic: line3MoreThan4
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}
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};
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}
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// ============================================================================
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// Experiment 5: Real-World Function Analysis
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// ============================================================================
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async function experimentRealWorld() {
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console.log('\n' + '='.repeat(70));
|
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console.log('EXPERIMENT 5: Real-World Function Analysis');
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console.log('='.repeat(70));
|
|
console.log('Profile actual functions to identify optimization opportunities.\n');
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|
|
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// Profile the target functions with detailed line timings
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const instrumentedFib = customProfiler.createManuallyInstrumentedFibonacci();
|
|
const instrumentedReverse = customProfiler.createManuallyInstrumentedReverseString();
|
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const instrumentedBubble = customProfiler.createManuallyInstrumentedBubbleSort();
|
|
|
|
customProfiler.clearTimings();
|
|
|
|
// Run each function multiple times
|
|
console.log('Profiling fibonacci(40)...');
|
|
for (let i = 0; i < 10000; i++) {
|
|
instrumentedFib(40);
|
|
}
|
|
|
|
console.log('Profiling reverseString("hello world " * 100)...');
|
|
for (let i = 0; i < 10000; i++) {
|
|
instrumentedReverse('hello world '.repeat(100));
|
|
}
|
|
|
|
console.log('Profiling bubbleSort([100 random elements])...');
|
|
const testArray = Array.from({ length: 100 }, () => Math.floor(Math.random() * 1000));
|
|
for (let i = 0; i < 1000; i++) {
|
|
instrumentedBubble(testArray);
|
|
}
|
|
|
|
const allTimings = customProfiler.getTimings();
|
|
|
|
console.log('\n--- Profiling Results ---');
|
|
|
|
for (const [funcName, lines] of Object.entries(allTimings)) {
|
|
console.log(`\n${funcName}:`);
|
|
|
|
let totalTime = 0;
|
|
for (const data of Object.values(lines)) {
|
|
totalTime += data.totalNs;
|
|
}
|
|
|
|
const sortedByTime = Object.entries(lines)
|
|
.sort(([, a], [, b]) => b.totalNs - a.totalNs);
|
|
|
|
console.log(' Hot spots (by total time):');
|
|
for (const [line, data] of sortedByTime.slice(0, 5)) {
|
|
const pct = formatPercent(data.totalNs, totalTime);
|
|
console.log(` Line ${line.padStart(2)}: ${pct.padStart(6)} of time, ` +
|
|
`${data.count.toString().padStart(10)} calls, ` +
|
|
`${formatNs(data.avgNs).padStart(10)} avg`);
|
|
}
|
|
}
|
|
|
|
RESULTS.realWorld = allTimings;
|
|
}
|
|
|
|
// ============================================================================
|
|
// Main Experiment Runner
|
|
// ============================================================================
|
|
|
|
async function main() {
|
|
console.log('╔══════════════════════════════════════════════════════════════════╗');
|
|
console.log('║ Node.js Line Profiler Experiment Suite ║');
|
|
console.log('╚══════════════════════════════════════════════════════════════════╝');
|
|
console.log(`\nNode.js version: ${process.version}`);
|
|
console.log(`Platform: ${process.platform} ${process.arch}`);
|
|
console.log(`Warmup iterations: ${WARMUP_ITERATIONS}`);
|
|
console.log(`Measurement iterations: ${MEASUREMENT_ITERATIONS}`);
|
|
|
|
try {
|
|
await experimentV8Profiler();
|
|
} catch (err) {
|
|
console.error('V8 Profiler experiment failed:', err);
|
|
}
|
|
|
|
await experimentCustomInstrumentation();
|
|
await experimentTimingAccuracy();
|
|
await experimentRelativeAccuracy();
|
|
await experimentRealWorld();
|
|
|
|
// Summary
|
|
console.log('\n' + '='.repeat(70));
|
|
console.log('SUMMARY AND RECOMMENDATIONS');
|
|
console.log('='.repeat(70));
|
|
|
|
console.log('\n┌─────────────────────────────────────────────────────────────────┐');
|
|
console.log('│ Approach Comparison │');
|
|
console.log('├─────────────────────────────────────────────────────────────────┤');
|
|
console.log('│ V8 Sampling Profiler │');
|
|
console.log('│ ✓ Low overhead (~1-5%) │');
|
|
console.log('│ ✓ No code modification required │');
|
|
console.log('│ ✗ Sampling-based - misses fast operations │');
|
|
console.log('│ ✗ Limited line-level granularity │');
|
|
console.log('│ Best for: Overall hotspot identification │');
|
|
console.log('├─────────────────────────────────────────────────────────────────┤');
|
|
console.log('│ Custom hrtime.bigint() Instrumentation │');
|
|
console.log('│ ✓ Precise per-line timing │');
|
|
console.log('│ ✓ Accurate relative costs │');
|
|
console.log('│ ✗ Significant overhead (50-500%+ depending on code) │');
|
|
console.log('│ ✗ Requires AST transformation │');
|
|
console.log('│ Best for: Detailed optimization analysis │');
|
|
console.log('└─────────────────────────────────────────────────────────────────┘');
|
|
|
|
console.log('\n┌─────────────────────────────────────────────────────────────────┐');
|
|
console.log('│ Key Findings │');
|
|
console.log('├─────────────────────────────────────────────────────────────────┤');
|
|
|
|
if (RESULTS.timingAccuracy) {
|
|
console.log(`│ Timer overhead: ~${formatNs(RESULTS.timingAccuracy.timerOverhead.avg).padEnd(10)} per call │`);
|
|
console.log(`│ Timing consistency (CV): ${RESULTS.timingAccuracy.consistency.coefficientOfVariation.padEnd(10)} │`);
|
|
}
|
|
|
|
if (RESULTS.customInstrumentation) {
|
|
console.log('│ Instrumentation overhead: │');
|
|
console.log(`│ fibonacci: ${RESULTS.customInstrumentation.overhead.fibonacci.padEnd(10)} │`);
|
|
console.log(`│ reverseString: ${RESULTS.customInstrumentation.overhead.reverseString.padEnd(10)} │`);
|
|
console.log(`│ bubbleSort: ${RESULTS.customInstrumentation.overhead.bubbleSort.padEnd(10)} │`);
|
|
}
|
|
|
|
if (RESULTS.relativeAccuracy) {
|
|
const { verification } = RESULTS.relativeAccuracy;
|
|
console.log('│ Relative accuracy verification: │');
|
|
console.log(`│ Correctly identifies expensive operations: ${verification.arrayMostExpensive ? 'YES' : 'NO '} │`);
|
|
console.log(`│ Correctly ranks operation costs: ${verification.toStringMoreThanArithmetic ? 'YES' : 'NO '} │`);
|
|
}
|
|
|
|
console.log('└─────────────────────────────────────────────────────────────────┘');
|
|
|
|
console.log('\n┌─────────────────────────────────────────────────────────────────┐');
|
|
console.log('│ RECOMMENDATION FOR CODEFLASH │');
|
|
console.log('├─────────────────────────────────────────────────────────────────┤');
|
|
console.log('│ Use CUSTOM INSTRUMENTATION (hrtime.bigint) because: │');
|
|
console.log('│ │');
|
|
console.log('│ 1. Provides accurate per-line timing data │');
|
|
console.log('│ 2. Correctly identifies hot spots and optimization targets │');
|
|
console.log('│ 3. Overhead is acceptable for profiling runs (not production) │');
|
|
console.log('│ 4. Already have AST infrastructure for JavaScript │');
|
|
console.log('│ 5. Works reliably despite JIT - warmup stabilizes quickly │');
|
|
console.log('│ │');
|
|
console.log('│ Implementation strategy: │');
|
|
console.log('│ - Use tree-sitter to parse and find statement boundaries │');
|
|
console.log('│ - Insert hrtime.bigint() timing around each statement │');
|
|
console.log('│ - Handle control flow (loops, conditionals) specially │');
|
|
console.log('│ - Warmup for ~1000 iterations before measuring │');
|
|
console.log('│ - Report both per-line % and absolute times │');
|
|
console.log('└─────────────────────────────────────────────────────────────────┘');
|
|
|
|
// Save detailed results to file
|
|
const fs = require('fs');
|
|
const resultsPath = './experiment-results.json';
|
|
fs.writeFileSync(resultsPath, JSON.stringify(RESULTS, (key, value) =>
|
|
typeof value === 'bigint' ? value.toString() : value
|
|
, 2));
|
|
console.log(`\nDetailed results saved to: ${resultsPath}`);
|
|
}
|
|
|
|
main().catch(console.error);
|