path: root/scripts/flame_graph.sh

#!/usr/bin/env bash

# Copyright (c) 2023 Egor Tensin <Egor.Tensin@gmail.com>
# This file is part of the "cimple" project.
# For details, see https://github.com/egor-tensin/cimple.
# Distributed under the MIT License.

# This script attaches to a set of processes and makes a flame graph using
# flamegraph.pl.

set -o errexit -o nounset -o pipefail
shopt -s inherit_errexit lastpipe

script_name="$( basename -- "${BASH_SOURCE[0]}" )"
readonly script_name

script_usage() {
    local msg
    for msg; do
        echo "$script_name: $msg"
    done

    echo "usage: $script_name OUTPUT_PATH PID [PID...]"
}

join_pids() {
    local result=''
    while [ "$#" -gt 0 ]; do
        if [ -n "$result" ]; then
            result="$result,"
        fi
        result="$result$1"
        shift
    done
    echo "$result"
}

output_dir=''

cleanup() {
    if [ -n "$output_dir" ]; then
        echo "Removing temporary directory: $output_dir"
        rm -rf -- "$output_dir"
    fi
}

make_graph() {
    wait "$record_pid" || true
    perf script -i "$output_dir/perf.data" > "$output_dir/perf.out"
    stackcollapse-perf.pl "$output_dir/perf.out" > "$output_dir/perf.folded"
    flamegraph.pl --width 2400 "$output_dir/perf.folded" > "$output_path"
}

record_pid=''

stop_record() {
    echo "Stopping 'perf record' process $record_pid"
    kill -SIGINT "$record_pid"
    make_graph
}

check_tools() {
    local tool
    for tool in perf stackcollapse-perf.pl flamegraph.pl; do
        if ! command -v "$tool" &> /dev/null; then
            echo "$script_name: $tool is missing" >&2
            exit 1
        fi
    done
}

main() {
    trap cleanup EXIT
    check_tools

    if [ "$#" -lt 1 ]; then
        script_usage "output path is required" >&2
        exit 1
    fi
    local output_path="$1"
    output_path="$( realpath -- "$output_path" )"
    shift

    if [ "$#" -lt 1 ]; then
        script_usage "at least one process ID is required" >&2
        exit 1
    fi
    local pids
    pids="$( join_pids "$@" )"
    shift

    echo "Output path: $output_path"
    echo "PIDs: $pids"

    output_dir="$( dirname -- "$output_path" )"
    output_dir="$( mktemp -d --tmpdir="$output_dir" )"
    readonly output_dir

    perf record \
        -o "$output_dir/perf.data" \
        --freq=99 \
        --call-graph dwarf,65528 \
        --pid="$pids" \
        --no-inherit &

    record_pid="$!"
    echo "Started 'perf record' process $record_pid"
    trap stop_record SIGINT SIGTERM

    make_graph
}

main "$@"