lix/contrib/stack-collapse.py

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#!/usr/bin/env nix-shell
#!nix-shell -i python3 -p python3 --pure
# To be used with `--trace-function-calls` and `flamegraph.pl`.
#
# For example:
#
# nix-instantiate --trace-function-calls '<nixpkgs>' -A hello 2> nix-function-calls.trace
# ./contrib/stack-collapse.py nix-function-calls.trace > nix-function-calls.folded
# nix-shell -p flamegraph --run "flamegraph.pl nix-function-calls.folded > nix-function-calls.svg"
import sys
from pprint import pprint
import fileinput
stack = []
timestack = []
for line in fileinput.input():
components = line.strip().split(" ", 2)
if components[0] != "function-trace":
continue
direction = components[1]
components = components[2].rsplit(" ", 2)
loc = components[0]
_at = components[1]
time = int(components[2])
if direction == "entered":
stack.append(loc)
timestack.append(time)
elif direction == "exited":
dur = time - timestack.pop()
vst = ";".join(stack)
print(f"{vst} {dur}")
stack.pop()