https://github.com/python/cpython/commit/b22d175c053b56fa534232715ff761a8cba9d636
commit: b22d175c053b56fa534232715ff761a8cba9d636
branch: main
author: Pablo Galindo Salgado <[email protected]>
committer: pablogsal <[email protected]>
date: 2026-08-25T23:32:34+01:00
summary:
gh-154088: Count elided stacks consistently (#154093)
files:
A Misc/NEWS.d/next/Library/2026-07-19-11-30-00.gh-issue-154088.pC7nRa.rst
M Lib/profiling/sampling/stack_collector.py
M Lib/test/test_profiling/test_sampling_profiler/test_collectors.py
diff --git a/Lib/profiling/sampling/stack_collector.py
b/Lib/profiling/sampling/stack_collector.py
index 97fe5535a6764c7..dd86d5d54a9aaa3 100644
--- a/Lib/profiling/sampling/stack_collector.py
+++ b/Lib/profiling/sampling/stack_collector.py
@@ -212,7 +212,7 @@ def _get_module_name(self, filename, path_info):
self._module_cache[filename] = module_name
return module_name
- def _convert_to_flamegraph_format(self):
+ def _convert_to_flamegraph_format(self, *, min_samples=None):
if self._total_samples == 0:
return {
"name": self._string_table.intern("No Data"),
@@ -302,7 +302,8 @@ def convert_children(children, min_samples, path_info):
# Filter out very small functions (less than 0.1% of total samples)
total_samples = self._total_samples
- min_samples = max(1, int(total_samples * 0.001))
+ if min_samples is None:
+ min_samples = max(1, int(total_samples * 0.001))
path_info = get_python_path_info()
root_children = convert_children(self._root["children"], min_samples,
path_info)
@@ -722,7 +723,15 @@ def _add_elided_flamegraph(self, current_flamegraph,
current_stats, baseline_sta
"""Calculate elided paths and add elided flamegraph to stats."""
self._elided_paths = baseline_stats.keys() - current_stats.keys()
- current_flamegraph["stats"]["elided_count"] = len(self._elided_paths)
+ # A sampled stack can end at an internal path that also has elided
+ # descendants. Count every disappeared path with self samples, not
+ # just the leaves of the elided path tree.
+ elided_stacks = {
+ path
+ for path in self._elided_paths
+ if baseline_stats[path]["self"] > 0
+ }
+ current_flamegraph["stats"]["elided_count"] = len(elided_stacks)
if self._elided_paths:
elided_flamegraph = self._build_elided_flamegraph(baseline_stats,
scale)
@@ -745,7 +754,9 @@ def _build_elided_flamegraph(self, baseline_stats, scale):
orig_get_source = self._baseline_collector._get_source_lines
self._baseline_collector._get_source_lines = lambda func: None
try:
- baseline_data =
self._baseline_collector._convert_to_flamegraph_format()
+ baseline_data =
self._baseline_collector._convert_to_flamegraph_format(
+ min_samples=1
+ )
finally:
self._baseline_collector._get_source_lines = orig_get_source
diff --git a/Lib/test/test_profiling/test_sampling_profiler/test_collectors.py
b/Lib/test/test_profiling/test_sampling_profiler/test_collectors.py
index 543ffc6fdd88d07..13e112f78014b9f 100644
--- a/Lib/test/test_profiling/test_sampling_profiler/test_collectors.py
+++ b/Lib/test/test_profiling/test_sampling_profiler/test_collectors.py
@@ -1665,7 +1665,7 @@ def test_diff_flamegraph_elided_stacks(self):
data = diff._convert_to_flamegraph_format()
- self.assertGreater(data["stats"]["elided_count"], 0)
+ self.assertEqual(data["stats"]["elided_count"], 1)
self.assertIn("elided_flamegraph", data["stats"])
elided = data["stats"]["elided_flamegraph"]
self.assertTrue(elided["stats"]["is_differential"])
@@ -1681,6 +1681,74 @@ def test_diff_flamegraph_elided_stacks(self):
self.assertGreater(child["baseline"], 0)
self.assertAlmostEqual(child["diff"], -child["baseline"])
+ def test_diff_flamegraph_counts_elided_stacks_not_paths(self):
+ """Internal and leaf stack endings are counted separately."""
+ internal_stack = [
+ MockInterpreterInfo(0, [
+ MockThreadInfo(1, [
+ MockFrameInfo("file.py", 20, "old_mid"),
+ MockFrameInfo("file.py", 10, "root"),
+ ])
+ ])
+ ]
+ leaf_stack = [
+ MockInterpreterInfo(0, [
+ MockThreadInfo(1, [
+ MockFrameInfo("file.py", 30, "old_leaf"),
+ MockFrameInfo("file.py", 20, "old_mid"),
+ MockFrameInfo("file.py", 10, "root"),
+ ])
+ ])
+ ]
+ current_frames = [
+ MockInterpreterInfo(0, [
+ MockThreadInfo(1, [MockFrameInfo("file.py", 10, "root")])
+ ])
+ ]
+
+ diff = make_diff_collector_with_mock_baseline(
+ [internal_stack, leaf_stack]
+ )
+ diff.collect(current_frames)
+
+ data = diff._convert_to_flamegraph_format()
+ self.assertEqual(data["stats"]["elided_count"], 2)
+
+ def test_diff_flamegraph_renders_small_elided_stack(self):
+ """Elided stacks are not removed by the significance filter."""
+ common_frames = [
+ MockInterpreterInfo(0, [
+ MockThreadInfo(1, [
+ MockFrameInfo("file.py", 20, "common"),
+ MockFrameInfo("file.py", 10, "root"),
+ ])
+ ])
+ ]
+ old_frames = [
+ MockInterpreterInfo(0, [
+ MockThreadInfo(1, [
+ MockFrameInfo("file.py", 30, "old_tiny"),
+ MockFrameInfo("file.py", 10, "root"),
+ ])
+ ])
+ ]
+
+ diff = make_diff_collector_with_mock_baseline(
+ [common_frames] * 1999 + [old_frames]
+ )
+ for _ in range(1999):
+ diff.collect(common_frames)
+
+ data = diff._convert_to_flamegraph_format()
+ self.assertEqual(data["stats"]["elided_count"], 1)
+ self.assertIn("elided_flamegraph", data["stats"])
+
+ elided = data["stats"]["elided_flamegraph"]
+ strings = elided["strings"]
+ self.assertIsNotNone(
+ find_child_by_name(elided.get("children", []), strings, "old_tiny")
+ )
+
def test_diff_flamegraph_elided_top_level_root(self):
"""Elided top-level roots do not crash metadata generation."""
baseline_frames_1 = [
diff --git
a/Misc/NEWS.d/next/Library/2026-07-19-11-30-00.gh-issue-154088.pC7nRa.rst
b/Misc/NEWS.d/next/Library/2026-07-19-11-30-00.gh-issue-154088.pC7nRa.rst
new file mode 100644
index 000000000000000..b9747589a2f1c8e
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-07-19-11-30-00.gh-issue-154088.pC7nRa.rst
@@ -0,0 +1,2 @@
+Make Tachyon count and render elided stacks consistently in differential
+flamegraphs.
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