gh-141592: final polish per review (docstring, unlink, with, comments)

Signed-off-by: Paresh Joshi <rahulj9223@gmail.com>

Author: pareshjoshij

Lib/test/test_perf_profiler.py

@@ -11,7 +11,7 @@
     assert_python_failure,
     assert_python_ok,
 )
-from test.support.os_helper import temp_dir
+from test.support.os_helper import temp_dir, unlink
 
 
 if not support.has_subprocess_support:
@@ -37,15 +37,8 @@ def supports_trampoline_profiling():
 class TestPerfTrampoline(unittest.TestCase):
 
     def _cleanup_perf_map(self, pid):
-        """
-        Helper to safely delete a specific perf map file.
-        """
-        perf_map = pathlib.Path(f"/tmp/perf-{pid}.map")
-        try:
-            if perf_map.exists():
-                perf_map.unlink()
-        except OSError:
-            pass
+        """Helper to safely delete a specific perf map file."""
+        unlink(f"/tmp/perf-{pid}.map")
 
     @unittest.skipIf(support.check_bolt_optimized(), "fails on BOLT instrumented binaries")
     def test_trampoline_works(self):
@@ -65,17 +58,14 @@ def baz():
             script = make_script(script_dir, "perftest", code)
             env = {**os.environ, "PYTHON_JIT": "0"}
 
-            process = subprocess.Popen(
+            with subprocess.Popen(
                 [sys.executable, "-Xperf", script],
                 text=True,
                 stderr=subprocess.PIPE,
                 stdout=subprocess.PIPE,
                 env=env,
-            )
-
-            self.addCleanup(self._cleanup_perf_map, process.pid)
-
-            with process:
+            ) as process:
+                self.addCleanup(self._cleanup_perf_map, process.pid)
                 stdout, stderr = process.communicate()
 
         self.assertEqual(stderr, "")
@@ -281,6 +271,8 @@ def perf_command_works():
     except (subprocess.SubprocessError, OSError):
         return False
 
+    # perf version does not return a version number on Fedora. Use presence
+    # of "perf.data" in help as indicator that it's perf from Linux tools.
     if "perf.data" not in stdout:
         return False
 
@@ -442,15 +434,8 @@ def baz(n):
 class TestPerfProfiler(unittest.TestCase, TestPerfProfilerMixin):
 
     def _cleanup_perf_map(self, pid):
-        """
-        Helper to safely delete a specific perf map file.
-        """
-        perf_map = pathlib.Path(f"/tmp/perf-{pid}.map")
-        try:
-            if perf_map.exists():
-                perf_map.unlink()
-        except OSError:
-            pass
+        """Helper to safely delete a specific perf map file."""
+        unlink(f"/tmp/perf-{pid}.map")
 
     def run_perf(self, script_dir, script, activate_trampoline=True):
         if activate_trampoline:
@@ -529,13 +514,21 @@ def compile_trampolines_for_all_functions():
         self.assertIn(f"py::foo_fork:{script}", child_perf_file_contents)
         self.assertIn(f"py::bar_fork:{script}", child_perf_file_contents)
 
+        # Pre-compiled perf-map entries of a forked process must be
+        # identical in both the parent and child perf-map files.
         perf_file_lines = perf_file_contents.split("\n")
         for line in perf_file_lines:
             if f"py::foo_fork:{script}" in line or f"py::bar_fork:{script}" in line:
                 self.assertIn(line, child_perf_file_contents)
 
 
 def _is_perf_version_at_least(major, minor):
+    # The output of perf --version looks like "perf version 6.7-3" but
+    # it can also be perf version "perf version 5.15.143", or even include
+    # a commit hash in the version string, like "6.12.9.g242e6068fd5c"
+    #
+    # PermissionError is raised if perf does not exist on the Windows Subsystem
+    # for Linux, see #134987
     try:
         output = subprocess.check_output(["perf", "--version"], text=True)
     except (subprocess.CalledProcessError, FileNotFoundError, PermissionError):