#!/bin/bash

# SPDX-FileCopyrightText: 2023 EfficiOS, Inc
#
# SPDX-License-Identifier: LGPL-2.1-only

CURDIR=$(dirname $0)/
TESTDIR=$CURDIR/..
source $TESTDIR/utils/tap.sh

plan_tests 1

: ${ITERS:=10}
: ${DURATION:=2}
: ${NR_THREADS:=1}
: ${NR_CPUS:=$(lscpu | grep "^CPU(s)" | sed 's/^.*:[ \t]*//g')}

: ${TIME:="./$CURDIR/ptime"}

: ${PROG_NOTRACING:="./$CURDIR/bench1 $NR_THREADS $DURATION"}
: ${PROG_TRACING:="./$CURDIR/bench2 $NR_THREADS $DURATION"}

function signal_cleanup ()
{
	killall lttng-sessiond
	exit
}

trap signal_cleanup SIGTERM SIGINT

CMD_NOTRACING="$TIME '$PROG_NOTRACING'"
CMD_TRACING="$TIME '$PROG_TRACING'"

NR_ACTIVE_CPUS=$(( $NR_CPUS > $NR_THREADS ? $NR_THREADS : $NR_CPUS ))

for i in $(seq $ITERS); do
	res=$(sh -c "$CMD_NOTRACING")
	loops_notrace[$i]=$(echo "${res}" | grep "^Number of loops:" | sed 's/^.*: //g')
	time_notrace[$i]=$(echo "${res}" | grep "^Wall time:" | sed 's/^.*: //g')
done

lttng-sessiond -d --no-kernel
lttng -q create --snapshot
lttng -q enable-event -u -a
lttng -q start

for i in $(seq $ITERS); do
	res=$(sh -c "$CMD_TRACING")
	loops_trace[$i]=$(echo "${res}" | grep "^Number of loops:" | sed 's/^.*: //g')
	time_trace[$i]=$(echo "${res}" | grep "^Wall time:" | sed 's/^.*: //g')
done

lttng -q stop
lttng -q destroy
killall lttng-sessiond

pass "Trace benchmark"

# Multiply the wall time by the number of active CPUs to get the
# overhead of events on each active cpu.

avg_delta=0
for i in $(seq $ITERS); do
	delta[$i]=$(echo "((${time_trace[$i]} * ${NR_ACTIVE_CPUS} / ${loops_trace[$i]}) - (${time_notrace[$i]} * ${NR_ACTIVE_CPUS} / ${loops_notrace[$i]}))" | bc -l)
	avg_delta=$(echo "(${avg_delta} + ${delta[$i]})" | bc -l)
done
avg_delta=$(echo "(${avg_delta} / $ITERS)" | bc -l)

std_dev=0
for i in $(seq $ITERS); do
	dev[$i]=$(echo "(( (${delta[$i]}) - (${avg_delta}) ) ^ 2)" | bc -l)
	std_dev=$(echo "( (${std_dev}) + (${dev[i]}) )" | bc -l)
done
std_dev=$(echo "( (${std_dev}) / $ITERS )" | bc -l)
std_dev=$(echo "(sqrt(${std_dev}))" | bc -l)

NS_PER_EVENT=$(echo "($avg_delta * 1000000000)" | bc -l)
# Remove fractions
NS_PER_EVENT=${NS_PER_EVENT%%.*}

STD_DEV_NS_PER_EVENT=$(echo "($std_dev * 1000000000)" | bc -l)
# Remove fractions
STD_DEV_NS_PER_EVENT=${STD_DEV_NS_PER_EVENT%%.*}

diag "Average tracing overhead per event is ${NS_PER_EVENT}ns, std.dev.: ${STD_DEV_NS_PER_EVENT}ns { NR_THREADS=${NR_THREADS}, NR_ACTIVE_CPUS=${NR_ACTIVE_CPUS} }"