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+# Inspector Protocol Collection in 0x
+
+This document describes how the 0x profiler collects performance data using V8's internal profiling mechanisms.
+
+## Overview
+
+The 0x profiler uses V8's built-in profiling capabilities rather than the Inspector Protocol directly. It leverages V8's `--prof` flag to generate isolate logs that contain performance sampling data.
+
+## Collection Flow
+
+```mermaid
+flowchart TD
+    A[User runs: 0x script.js] --> B[cmd.js parses arguments]
+    B --> C[index.js calls platform/v8.js]
+    C --> D[Spawn Node.js process with --prof flag]
+    D --> E[V8 generates isolate log file]
+
+    D --> F[Process executes user script]
+    F --> G[V8 samples execution stack at regular intervals]
+    G --> H[Samples written to isolate-*.log file]
+
+    D --> I[Collect inlining info from --print-opt-source]
+    I --> J[Parse optimization logs for INLINE statements]
+    J --> K[Build inlining metadata]
+
+    H --> L[Process exits]
+    L --> M[Move isolate log to target folder]
+    M --> N[v8LogToTicks processes the log]
+
+    N --> O[Preprocess log file for compatibility]
+    O --> P[Run node --prof-process --preprocess]
+    P --> Q[Parse JSON stream for 'code' events]
+    Q --> R[Parse JSON stream for 'ticks' events]
+
+    R --> S[Build code address mapping]
+    S --> T[Convert ticks to stack traces]
+    T --> U[Filter by collectDelay if specified]
+    U --> V[Return processed ticks array]
+
+    V --> W[ticksToTree converts to tree structure]
+    W --> X[render.js generates flamegraph]
+    X --> Y[Final HTML flamegraph output]
+
+    style D fill:#e1f5fe
+    style E fill:#e8f5e8
+    style H fill:#e8f5e8
+    style P fill:#fff3e0
+    style V fill:#f3e5f5
+    style Y fill:#ffebee
+```
+
+## Key Components
+
+### 1. Process Spawning (platform/v8.js)
+- Spawns Node.js with `--prof` flag to enable V8 profiling
+- Adds `--logfile` to specify isolate log location
+- Includes `--print-opt-source` for optimization information
+- Preloads modules for process control and port detection
+
+### 2. Isolate Log Generation
+- V8 automatically generates isolate log files with format: `isolate-{address}-{pid}-{pid}-v8.log`
+- Contains sampling data with stack traces and timing information
+- Records code events (function compilation, optimization)
+- Records tick events (periodic stack samples)
+
+### 3. Inlining Information Collection
+- Monitors stdout for optimization logs from `--print-opt-source`
+- Parses `INLINE()` statements to track function inlining
+- Builds metadata about which functions were inlined and where
+- Associates inlined functions with their call sites
+
+### 4. Log Processing (lib/v8-log-to-ticks.js)
+- Preprocesses isolate log for compatibility across Node.js versions
+- Runs `node --prof-process --preprocess` to convert to JSON
+- Streams JSON parsing to handle large log files
+- Extracts code events to build address-to-function mapping
+- Extracts tick events to get stack sample data
+
+### 5. Data Transformation
+- Maps raw addresses in tick samples to actual function names
+- Applies collectDelay filtering to ignore initial samples
+- Reverses stack order for proper call hierarchy
+- Filters out invalid or incomplete samples
+
+### 6. Output Generation
+- Converts processed ticks to hierarchical tree structure
+- Renders interactive HTML flamegraph visualization
+- Preserves inlining information for detailed analysis
+
+## Technical Details
+
+### V8 Profiling Flags
+- `--prof`: Enable V8 profiling and generate isolate log
+- `--logfile=%p-v8.log`: Specify log filename pattern with PID
+- `--print-opt-source`: Output optimization information to stdout
+
+### Data Flow
+1. **Sampling**: V8 periodically samples the call stack (every ~1ms)
+2. **Logging**: Stack samples written to isolate log with timestamps
+3. **Processing**: Log converted to JSON format for parsing
+4. **Mapping**: Raw addresses mapped to function names and locations
+5. **Aggregation**: Samples grouped and counted to build execution profile
+
+### Compatibility Handling
+- Different preprocessing for Node.js versions 8, 10, and 11+
+- Handles V8 log format changes across versions
+- Escapes problematic characters that break preprocessing
+- Filters out excessively long log lines that cause crashes
+
+## Benefits of This Approach
+
+- **Low Overhead**: Uses V8's built-in sampling profiler
+- **High Accuracy**: Captures actual execution without instrumentation
+- **Complete Coverage**: Profiles both JavaScript and native code
+- **Inlining Aware**: Tracks function inlining for accurate attribution
+- **Version Compatible**: Works across different Node.js versions
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