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@softwaredoug
Last active January 3, 2024 22:50
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VisualVM Forward Calls Stacktrace to Flamegraph format
"""Parses a VisualVM Forward Call Tree CSV file and outputs a flamegraph.
In VisualVM CPU Snapshot, select "Export", and choose "Forward Call Tree" and save
as CSV. The input will look something like:
"org.apache.spark.util.collection.ExternalSorter.writePartitionedFile(ExternalSorter.java:388)", "1,252 ms (100.0%)"
" Self time", "1 ms (0.01%)"
" org.apache.spark.util.collection.ExternalSorter.someOtherFunction(ExternalSorter.java:388)", "1,150 ms (95.0%)"
" Self time", "75 ms (5.0%)"
(Other calls from of someOtherFunction)
"org.apache.spark.util.collection.ExternalSorter.doAThing(ExternalSorter.java:388)", "1,150 ms (95.0%)"
The output is a flattened callstack with the time spent in each function consumable by the Brendan Gregg's flamegraph.pl script.
org.apache.spark.util.collection.ExternalSorter.writePartitionedFile(ExternalSorter.java:388) 1252
org.apache.spark.util.collection.ExternalSorter.writePartitionedFile(ExternalSorter.java:388);org.apache.spark.util.collection.ExternalSorter.someOtherFunction(ExternalSorter.java:388) 1150
and so on
Usage:
python parse_stack.py <path to csv file> > stacks.txt
The output can be used with flamegraph.pl to generate a flamegraph as follows:
./flamegraph.pl --title="My Flamegraph" stacks.txt > flamegraph.svg
Open the file in a browser to view the flamegraph.
"""
import csv
import sys
def read_csv(filename):
"""Reads a CSV file and returns a list of lists."""
with open(filename, 'r') as f:
reader = csv.reader(f)
# Skip headers
next(reader)
return list(reader)
def flatten_callstack(table):
"""Flattens a callstack table."""
stacks = []
for idx, row in enumerate(table):
call = row[0]
my_time = float(row[1].replace(',', '').split()[0])
my_hits = int(row[3].replace(',', ''))
call_strip = call.strip()
if call_strip == 'Self time':
continue
spaces_before = len(call) - len(call.lstrip())
my_stack = [call_strip]
# Read backwards to get calls indented less than my call
for prev_row in reversed(table[:idx]):
prev_call = prev_row[0]
prev_call_strip = prev_call.strip()
if prev_call_strip == 'Self time':
continue
prev_spaces_before = len(prev_call) - len(prev_call.lstrip())
if prev_spaces_before < spaces_before:
# This is a parent call, prepend it, remember current indentation level
# so we don't get siblings
my_stack.insert(0, prev_call_strip)
spaces_before = prev_spaces_before
stacks.append((my_stack, my_time, my_hits))
return stacks
def to_flamegraph_format(stacks):
"""Converts a list of stacks to flamegraph format."""
for stack, _, hits in stacks:
print(';'.join(stack), hits)
def main(jmx_path):
data = read_csv(jmx_path)
flattened = flatten_callstack(data)
to_flamegraph_format(flattened)
if __name__ == '__main__':
main(sys.argv[1])
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