cpython/Lib/profiling/sampling/stack_collector.py
László Kiss Kollár 3e06cfcaee
gh-135953: Reduce memory usage of stack collectors (#138875)
The stack collector base class keeps all frames until export() is
called, which causes significant unnecessary memory usage. Instead, we
can process the frames on the fly in the collect call by dispatching the
aggregation logic to the subclass through the process_frames method.

Co-authored-by: Pablo Galindo Salgado <pablogsal@gmail.com>
2025-09-14 23:47:14 +01:00

276 lines
9.7 KiB
Python

import base64
import collections
import functools
import importlib.resources
import json
import linecache
import os
from .collector import Collector
from .string_table import StringTable
class StackTraceCollector(Collector):
def collect(self, stack_frames):
for frames in self._iter_all_frames(stack_frames):
if not frames:
continue
self.process_frames(frames)
def process_frames(self, frames):
pass
class CollapsedStackCollector(StackTraceCollector):
def __init__(self):
self.stack_counter = collections.Counter()
def process_frames(self, frames):
call_tree = tuple(reversed(frames))
self.stack_counter[call_tree] += 1
def export(self, filename):
lines = []
for call_tree, count in self.stack_counter.items():
stack_str = ";".join(
f"{os.path.basename(f[0])}:{f[2]}:{f[1]}" for f in call_tree
)
lines.append((stack_str, count))
lines.sort(key=lambda x: (-x[1], x[0]))
with open(filename, "w") as f:
for stack, count in lines:
f.write(f"{stack} {count}\n")
print(f"Collapsed stack output written to {filename}")
class FlamegraphCollector(StackTraceCollector):
def __init__(self):
self.stats = {}
self._root = {"samples": 0, "children": {}}
self._total_samples = 0
self._func_intern = {}
self._string_table = StringTable()
def set_stats(self, sample_interval_usec, duration_sec, sample_rate, error_rate=None):
"""Set profiling statistics to include in flamegraph data."""
self.stats = {
"sample_interval_usec": sample_interval_usec,
"duration_sec": duration_sec,
"sample_rate": sample_rate,
"error_rate": error_rate
}
def export(self, filename):
flamegraph_data = self._convert_to_flamegraph_format()
# Debug output with string table statistics
num_functions = len(flamegraph_data.get("children", []))
total_time = flamegraph_data.get("value", 0)
string_count = len(self._string_table)
print(
f"Flamegraph data: {num_functions} root functions, total samples: {total_time}, "
f"{string_count} unique strings"
)
if num_functions == 0:
print(
"Warning: No functions found in profiling data. Check if sampling captured any data."
)
return
html_content = self._create_flamegraph_html(flamegraph_data)
with open(filename, "w", encoding="utf-8") as f:
f.write(html_content)
print(f"Flamegraph saved to: {filename}")
@staticmethod
@functools.lru_cache(maxsize=None)
def _format_function_name(func):
filename, lineno, funcname = func
if len(filename) > 50:
parts = filename.split("/")
if len(parts) > 2:
filename = f".../{'/'.join(parts[-2:])}"
return f"{funcname} ({filename}:{lineno})"
def _convert_to_flamegraph_format(self):
"""Convert aggregated trie to d3-flamegraph format with string table optimization."""
if self._total_samples == 0:
return {
"name": self._string_table.intern("No Data"),
"value": 0,
"children": [],
"strings": self._string_table.get_strings()
}
def convert_children(children, min_samples):
out = []
for func, node in children.items():
samples = node["samples"]
if samples < min_samples:
continue
# Intern all string components for maximum efficiency
filename_idx = self._string_table.intern(func[0])
funcname_idx = self._string_table.intern(func[2])
name_idx = self._string_table.intern(self._format_function_name(func))
child_entry = {
"name": name_idx,
"value": samples,
"children": [],
"filename": filename_idx,
"lineno": func[1],
"funcname": funcname_idx,
}
source = self._get_source_lines(func)
if source:
# Intern source lines for memory efficiency
source_indices = [self._string_table.intern(line) for line in source]
child_entry["source"] = source_indices
# Recurse
child_entry["children"] = convert_children(
node["children"], min_samples
)
out.append(child_entry)
# Sort by value (descending) then by name index for consistent ordering
out.sort(key=lambda x: (-x["value"], x["name"]))
return out
# 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))
root_children = convert_children(self._root["children"], min_samples)
if not root_children:
return {
"name": self._string_table.intern("No significant data"),
"value": 0,
"children": [],
"strings": self._string_table.get_strings()
}
# If we only have one root child, make it the root to avoid redundant level
if len(root_children) == 1:
main_child = root_children[0]
# Update the name to indicate it's the program root
old_name = self._string_table.get_string(main_child["name"])
new_name = f"Program Root: {old_name}"
main_child["name"] = self._string_table.intern(new_name)
main_child["stats"] = self.stats
main_child["strings"] = self._string_table.get_strings()
return main_child
return {
"name": self._string_table.intern("Program Root"),
"value": total_samples,
"children": root_children,
"stats": self.stats,
"strings": self._string_table.get_strings()
}
def process_frames(self, frames):
# Reverse to root->leaf
call_tree = reversed(frames)
self._root["samples"] += 1
self._total_samples += 1
current = self._root
for func in call_tree:
func = self._func_intern.setdefault(func, func)
children = current["children"]
node = children.get(func)
if node is None:
node = {"samples": 0, "children": {}}
children[func] = node
node["samples"] += 1
current = node
def _get_source_lines(self, func):
filename, lineno, _ = func
try:
lines = []
start_line = max(1, lineno - 2)
end_line = lineno + 3
for line_num in range(start_line, end_line):
line = linecache.getline(filename, line_num)
if line.strip():
marker = "" if line_num == lineno else " "
lines.append(f"{marker}{line_num}: {line.rstrip()}")
return lines if lines else None
except Exception:
return None
def _create_flamegraph_html(self, data):
data_json = json.dumps(data)
template_dir = importlib.resources.files(__package__)
vendor_dir = template_dir / "_vendor"
assets_dir = template_dir / "_assets"
d3_path = vendor_dir / "d3" / "7.8.5" / "d3.min.js"
d3_flame_graph_dir = vendor_dir / "d3-flame-graph" / "4.1.3"
fg_css_path = d3_flame_graph_dir / "d3-flamegraph.css"
fg_js_path = d3_flame_graph_dir / "d3-flamegraph.min.js"
fg_tooltip_js_path = d3_flame_graph_dir / "d3-flamegraph-tooltip.min.js"
html_template = (template_dir / "flamegraph_template.html").read_text(encoding="utf-8")
css_content = (template_dir / "flamegraph.css").read_text(encoding="utf-8")
js_content = (template_dir / "flamegraph.js").read_text(encoding="utf-8")
# Inline first-party CSS/JS
html_template = html_template.replace(
"<!-- INLINE_CSS -->", f"<style>\n{css_content}\n</style>"
)
html_template = html_template.replace(
"<!-- INLINE_JS -->", f"<script>\n{js_content}\n</script>"
)
png_path = assets_dir / "python-logo-only.png"
b64_logo = base64.b64encode(png_path.read_bytes()).decode("ascii")
# Let CSS control size; keep markup simple
logo_html = f'<img src="data:image/png;base64,{b64_logo}" alt="Python logo"/>'
html_template = html_template.replace("<!-- INLINE_LOGO -->", logo_html)
d3_js = d3_path.read_text(encoding="utf-8")
fg_css = fg_css_path.read_text(encoding="utf-8")
fg_js = fg_js_path.read_text(encoding="utf-8")
fg_tooltip_js = fg_tooltip_js_path.read_text(encoding="utf-8")
html_template = html_template.replace(
"<!-- INLINE_VENDOR_D3_JS -->",
f"<script>\n{d3_js}\n</script>",
)
html_template = html_template.replace(
"<!-- INLINE_VENDOR_FLAMEGRAPH_CSS -->",
f"<style>\n{fg_css}\n</style>",
)
html_template = html_template.replace(
"<!-- INLINE_VENDOR_FLAMEGRAPH_JS -->",
f"<script>\n{fg_js}\n</script>",
)
html_template = html_template.replace(
"<!-- INLINE_VENDOR_FLAMEGRAPH_TOOLTIP_JS -->",
f"<script>\n{fg_tooltip_js}\n</script>",
)
# Replace the placeholder with actual data
html_content = html_template.replace(
"{{FLAMEGRAPH_DATA}}", data_json
)
return html_content