[gh-135953] Profile a module or script with sampling profiler #136777
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Add `-m` and `filename` arguments to the sampling profiler to launch the specified Python program in a subprocess and start profiling it. Previously only a PID was accepted, this can now be done by passing `-p PID`.
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Pull Request Overview
This PR extends the sampling profiler to support profiling modules and scripts by launching them in subprocesses, in addition to the existing PID-based profiling. The change improves the usability of the profiler by allowing users to profile Python programs from startup rather than only attaching to existing processes.
- Adds
-mand script filename arguments as mutually exclusive alternatives to the existing-p PIDoption - Updates argument parsing to handle the new target modes with proper validation
- Implements subprocess management with graceful termination handling
Reviewed Changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.
| File | Description |
|---|---|
| Lib/profile/sample.py | Adds argument parsing for module and script modes, implements subprocess launching and management |
| Lib/test/test_sample_profiler.py | Updates existing CLI tests to use -p flag and adds comprehensive test coverage for new module/script functionality |
Comments suppressed due to low confidence (1)
Lib/test/test_sample_profiler.py:1637
- The test uses
contextlib.chdir()to change directories for module discovery, but doesn't test the case where the module is not found or the directory change fails. Consider adding a test case for module resolution errors.
contextlib.chdir(tempdir.name),
| if not(args.pid or args.module or args.script): | ||
| parser.error( | ||
| "You must specify either a process ID (-p), a module (-m), or a script to run." | ||
| ) |
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The condition not(args.pid or args.module or args.script) is redundant since the mutually exclusive group is already marked as required=True. The argparse library will automatically enforce that one of these options is provided.
| if not(args.pid or args.module or args.script): | |
| parser.error( | |
| "You must specify either a process ID (-p), a module (-m), or a script to run." | |
| ) | |
| # The mutually exclusive group already enforces that one of these arguments is required. |
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| process = subprocess.Popen(cmd) | ||
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| try: | ||
| exit_code = process.wait(timeout=0.1) |
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The hardcoded timeout of 0.1 seconds is a magic number. Consider defining this as a named constant or making it configurable, as some programs may have longer startup times.
| exit_code = process.wait(timeout=0.1) | |
| exit_code = process.wait(timeout=DEFAULT_PROCESS_WAIT_TIMEOUT) |
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| if process.poll() is None: | ||
| process.terminate() | ||
| try: | ||
| process.wait(timeout=2) |
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The hardcoded timeout of 2 seconds for graceful termination is a magic number. Consider defining this as a named constant for better maintainability.
| process.wait(timeout=2) | |
| process.wait(timeout=GRACEFUL_TERMINATION_TIMEOUT_SEC) |
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| process = subprocess.Popen(cmd) | ||
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| try: | ||
| exit_code = process.wait(timeout=0.1) |
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Hummm, why is this? Just in case the process fails immediately?
Add
-mandfilenamearguments to the sampling profiler to launch the specified Python program in a subprocess and start profiling it. Previously only a PID was accepted, this can now be done by passing-p PID.