Add docs/tech_docs/python/perf.md

docs/tech_docs/python/perf.md

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+In the domain of system monitoring and performance analysis on Linux, the `psutil` library emerges as a critical tool, enabling Python applications to gather system utilization data and perform process management. However, for developers and system administrators seeking to delve deeper into system performance analysis and diagnostics, `perf` stands out as a key tool within the Linux ecosystem, though not directly accessible via a standard Python library.
+
+`perf` is a powerful performance counter for Linux, offering access to a wide range of hardware performance counters, such as CPU cycles, instructions per cycle, cache hits and misses, and more. While `perf` itself is a command-line tool rather than a Python library, Python can interact with `perf` data or use it as part of a larger Python-driven monitoring or performance analysis solution.
+
+Since there isn't a direct Python library for `perf`, the integration usually involves using Python to automate `perf` command execution, parse its output, and possibly visualize the data. This approach leverages Python's capabilities for data manipulation and analysis to work with the rich, low-level performance data that `perf` provides.
+
+### Automating `perf` with Python
+
+#### Running `perf` Commands from Python
+You can use Python's `subprocess` module to run `perf` commands and capture their output for analysis:
+
+```python
+import subprocess
+
+def run_perf_command(command):
+    result = subprocess.run(["perf", *command.split()], capture_output=True, text=True)
+    if result.returncode == 0:
+        return result.stdout
+    else:
+        raise Exception(f"perf command failed: {result.stderr}")
+
+# Example usage
+output = run_perf_command("stat -e cycles,instructions ls")
+print(output)
+```
+
+#### Parsing `perf` Output
+Once you've captured the output from `perf`, you can use Python to parse and analyze the data. The parsing complexity depends on the specific `perf` command and the data you're interested in:
+
+```python
+def parse_perf_stat_output(output):
+    metrics = {}
+    for line in output.splitlines():
+        if "cycles" in line or "instructions" in line:
+            parts = line.split()
+            metrics[parts[1]] = parts[0]
+    return metrics
+
+# Example usage
+metrics = parse_perf_stat_output(output)
+print(metrics)
+```
+
+#### Visualizing `perf` Data
+With the parsed data, you can utilize libraries such as `matplotlib` or `pandas` for visualization:
+
+```python
+import matplotlib.pyplot as plt
+
+def plot_metrics(metrics):
+    labels = metrics.keys()
+    values = [int(v.replace(',', '')) for v in metrics.values()]
+    
+    plt.bar(labels, values)
+    plt.xlabel('Metric')
+    plt.ylabel('Value')
+    plt.title('Performance Metrics')
+    plt.show()
+
+# Example usage
+plot_metrics(metrics)
+```
+
+### Use Cases
+- **Performance Analysis**: Automated performance regression testing or benchmarking.
+- **System Monitoring**: Building custom monitoring solutions that require access to hardware performance counters.
+- **Profiling**: Identifying performance bottlenecks in applications.
+
+### Considerations
+- **Permissions**: Running `perf` might require elevated permissions depending on the counters accessed.
+- **Complexity**: The `perf` tool can generate vast amounts of data; focus on specific metrics relevant to your analysis to manage complexity.
+
+While not a straightforward Python library integration, the combination of Python and `perf` on Linux unlocks powerful capabilities for performance analysis and monitoring. It exemplifies Python's versatility in system-level integration and automation, providing developers and system administrators with tools to analyze and improve system and application performance.