#!/bin/bash
# -*- tab-width: 4; indent-tabs-mode: nil; py-indent-offset: 4 -*-
#
# Copyright the Collabora Online contributors.
#
# SPDX-License-Identifier: MPL-2.0
#
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.
#

# generate output for flamegraph from incremental perf record 100M dumps
# e.g. perf-record-stackcollapse -e probe:do_wp_page -F5 --call-graph dwarf,32768 -a sleep 10s

# perf record typically uses a huge amount of disk space by default
# there is perf record -i - to stream instead, but:
# a) That pipe-mode format is different than the typical to-disk format.
# In current (6.12) versions, perf record -o - | perf script -i
# results in lines like:
#     5580366425ee cmd_record
#     5580366af1bf [unknown]
#     5580366af4da [unknown]
#     5580366297df main
# while perf record+script file mode, results in lines like:
#     55a58d6785ee cmd_record+0xdde (/usr/bin/whatever)
#     55a58d6e51bf [unknown] (/usr/bin/whatever)
#     55a58d6e54da [unknown] (/usr/bin/whatever)
#     55a58d65f7df main+0x2ff (/usr/bin/whatever)
# And flamegraph wants the 2nd format, that's a relatively minor problem
# which could be worked around, but:
# b) earlier versions of perf record (4.20.16) don't appear to record callgraphs
# at all in pipe-mode, or perf script cannot output them
# So, easiest thing seems to be to use switch-output, and run each incremental
# perf dump through stackcollapse-perf.pl before deleting the perf dump

# Notes:
# building perf standalone: https://medium.com/@manas.marwah/building-perf-tool-fc838f084f71
# perf-4.20.16 seen with maps__fixup_overlappings hang on perf script:
#   https://lkml.iu.edu/hypermail/linux/kernel/1912.1/05324.html
if ! test `id -u` = 0; then
    echo "not root, if this doesn't work try sudo profile-cool"
fi
if ! which stackcollapse-perf.pl > /dev/null 2>&1; then
    REAL_USER_HOME="$(getent passwd $SUDO_USER | cut -d: -f6)"
    PATH=$PATH:$HOME/FlameGraph:$REAL_USER_HOME/FlameGraph
fi
if ! which stackcollapse-perf.pl > /dev/null 2>&1; then
    echo "no stackcollapse-perf.pl found"
    echo "On fedora install systemwide with: sudo dnf install flamegraph"
    echo "Otherwise install locally manually into ~/FlameGraph"
    echo "    e.g. git clone https://github.com/brendangregg/FlameGraph ~/FlameGraph"
    exit 1
fi

PERF="${PERF:-perf}"

set -e

WORK_DIR=`mktemp -d -p /var/tmp`
pushd "$WORK_DIR" > /dev/null
echo spooling profiling to "$WORK_DIR" 1>&2

{ $PERF record --switch-output=100M -o perf.data $* && touch stacks.stop; } &

{ (echo "$BASHPID" > "$WORK_DIR/inotifywait.pid"; exec inotifywait -m . -e close_write) |
    while read dir action file; do
        if [[ "$file" == "stacks.stop" ]]; then
            rm stacks.stop
            kill `cat "$WORK_DIR/inotifywait.pid"`
            rm "$WORK_DIR/inotifywait.pid"
        fi
        if [[ "$file" == perf.data.* ]]; then
            $PERF script --no-inline -i "$file" | stackcollapse-perf.pl
            rm "$file"
        fi
    done; } &

wait

rm -rf "$WORK_DIR"
popd > /dev/null
echo profiling complete 1>&2

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