[3.15] gh-150723: Fix perf jitdump files on macOS (GH-150728)

Lib/test/test_samply_profiler.py

@@ -240,5 +240,29 @@ def compile_trampolines_for_all_functions():
                 self.assertIn(line, child_perf_file_contents)
 
 
+@unittest.skipUnless(samply_command_works(), "samply command doesn't work")
+class TestSamplyProfilerWithJitDump(unittest.TestCase, TestSamplyProfilerMixin):
+    # Regression test for gh-150723: exercises the binary jitdump backend
+    # (-Xperf_jit) end to end through samply, unlike TestSamplyProfiler which
+    # uses the textual perf-map backend (-Xperf).
+    def run_samply(self, script_dir, script, activate_trampoline=True):
+        if activate_trampoline:
+            return run_samply(script_dir, sys.executable, "-Xperf_jit", script)
+        return run_samply(script_dir, sys.executable, script)
+
+    def setUp(self):
+        super().setUp()
+        self.jit_files = set(pathlib.Path("/tmp/").glob("jit-*.dump"))
+        self.jit_files |= set(pathlib.Path("/tmp/").glob("jitted-*.so"))
+
+    def tearDown(self) -> None:
+        super().tearDown()
+        files_to_delete = set(pathlib.Path("/tmp/").glob("jit-*.dump"))
+        files_to_delete |= set(pathlib.Path("/tmp/").glob("jitted-*.so"))
+        files_to_delete -= self.jit_files
+        for file in files_to_delete:
+            file.unlink()
+
+
 if __name__ == "__main__":
     unittest.main()

Misc/NEWS.d/next/Core_and_Builtins/2026-06-01-19-21-01.gh-issue-150723.Hb3JDG.rst

@@ -0,0 +1,4 @@
+Fix malformed perf jitdump thread ids on macOS. The ``thread_id`` field of the
+``JR_CODE_LOAD`` record was written as a 64-bit value instead of the 32-bit
+value required by the jitdump format, which shifted every following field and
+prevented profilers from resolving Python frames.

Misc/NEWS.d/next/Core_and_Builtins/2026-06-01-19-24-12.gh-issue-150723.WlcL_-.rst

@@ -0,0 +1,4 @@
+Fix perf jitdump timestamps on macOS. Events were stamped using
+``CLOCK_MONOTONIC``, but macOS profilers timestamp their samples with
+``mach_absolute_time()``. The mismatch prevented the JIT code mappings from
+lining up with the samples, so no Python frame could be resolved.

Python/perf_jit_trampoline.c

@@ -82,6 +82,9 @@
 #if defined(__linux__)
 #  include <sys/syscall.h>        // System call interface
 #endif
+#if defined(__APPLE__)
+#  include <mach/mach_time.h>     // mach_absolute_time, mach_timebase_info
+#endif
 
 // =============================================================================
 //                           CONSTANTS AND CONFIGURATION
@@ -217,11 +220,7 @@ struct BaseEvent {
 typedef struct {
     struct BaseEvent base;   // Common event header
     uint32_t process_id;     // Process ID where code was generated
-#if defined(__APPLE__)
-    uint64_t thread_id;      // Thread ID where code was generated
-#else
     uint32_t thread_id;      // Thread ID where code was generated
-#endif
     uint64_t vma;            // Virtual memory address where code is loaded
     uint64_t code_address;   // Address of the actual machine code
     uint64_t code_size;      // Size of the machine code in bytes
@@ -295,7 +294,9 @@ static PerfMapJitState perf_jit_map_state;
 // =============================================================================
 
 /* Time conversion constant */
+#if !defined(__APPLE__)
 static const intptr_t nanoseconds_per_second = 1000000000;
+#endif
 
 /*
  * Get current monotonic time in nanoseconds
@@ -307,6 +308,18 @@ static const intptr_t nanoseconds_per_second = 1000000000;
  * Returns: Current monotonic time in nanoseconds since an arbitrary epoch
  */
 static int64_t get_current_monotonic_ticks(void) {
+#if defined(__APPLE__)
+    // On macOS the jitdump file is consumed by profilers (such as samply) that
+    // timestamp their samples using mach_absolute_time(). The jitdump event
+    // timestamps must use the same clock domain, otherwise the JIT code
+    // mappings cannot be lined up with the samples.
+    static mach_timebase_info_data_t timebase = {0, 0};
+    if (timebase.denom == 0) {
+        (void)mach_timebase_info(&timebase);
+    }
+    uint64_t ticks = mach_absolute_time();
+    return (int64_t)(ticks * timebase.numer / timebase.denom);
+#else
     struct timespec ts;
     if (clock_gettime(CLOCK_MONOTONIC, &ts) != 0) {
         Py_UNREACHABLE();  // Should never fail on supported systems
@@ -318,6 +331,7 @@ static int64_t get_current_monotonic_ticks(void) {
     result *= nanoseconds_per_second;
     result += ts.tv_nsec;
     return result;
+#endif
 }
 
 /*
@@ -652,7 +666,12 @@ static void perf_map_jit_write_entry_with_name(
     ev.base.time_stamp = get_current_monotonic_ticks();
     ev.process_id = getpid();
 #if defined(__APPLE__)
-    pthread_threadid_np(NULL, &ev.thread_id);
+    // The jitdump format defines the thread id field as a 32-bit value, but
+    // pthread_threadid_np() returns a 64-bit id. Truncate it to 32 bits to
+    // keep the record layout identical to other platforms.
+    uint64_t thread_id = 0;
+    pthread_threadid_np(NULL, &thread_id);
+    ev.thread_id = (uint32_t)thread_id;
 #else
     ev.thread_id = syscall(SYS_gettid);  // Get thread ID via system call
 #endif