diff mbox series

[RFC,v2,2/2] selftest/cpuidle: Add support for cpuidle latency measurement

Message ID 20210401114504.13466-3-psampat@linux.ibm.com (mailing list archive)
State New
Headers show
Series CPU-Idle latency selftest framework | expand

Commit Message

Pratik R. Sampat April 1, 2021, 11:45 a.m. UTC
The cpuidle latency selftest provides support to systematically extract,
analyse and present IPI and timer based wakeup latencies for each CPU
and each idle state available on the system.

The selftest leverages test-cpuidle_latency module's debugfs interface
to interact and extract latency information from the kernel.

The selftest inserts the module if already not inserted, disables all
the idle states and enables them one by one testing the following:
1. Keeping source CPU constant, iterate through all the CPUS measuring
  IPI latency for baseline (CPU is busy with cat /dev/random > /dev/null
  workload) and then when the CPU is allowed to be at rest
2. Iterating through all the CPUs, sending expected timer durations to
  be equivalent to the residency of the deepest idle state enabled
  and extracting the difference in time between the time of wakeup and
  the expected timer duration

The timer based test produces run to run variance on some intel based
systems that sport a mechansim "C-state pre-wake" which can
pre-wake a CPU from an idle state when timers are armed. For systems and
architectures that don't have this mechansim can leverage timer tests
with the -i option.

To run this test specifically:
$ make -C tools/testing/selftests TARGETS="cpuidle" run_tests

There are a few optinal arguments too that the script can take
        [-h <help>]
        [-i <run timer tests>]
        [-m <location of the module>]
        [-o <location of the output>]
        [-v <verbose> (run on all cpus)]
Default Output location in: tools/testing/selftest/cpuidle/cpuidle.log

Signed-off-by: Pratik Rajesh Sampat <psampat@linux.ibm.com>
---
 tools/testing/selftests/Makefile           |   1 +
 tools/testing/selftests/cpuidle/Makefile   |   6 +
 tools/testing/selftests/cpuidle/cpuidle.sh | 323 +++++++++++++++++++++
 tools/testing/selftests/cpuidle/settings   |   2 +
 4 files changed, 332 insertions(+)
 create mode 100644 tools/testing/selftests/cpuidle/Makefile
 create mode 100755 tools/testing/selftests/cpuidle/cpuidle.sh
 create mode 100644 tools/testing/selftests/cpuidle/settings

Comments

Doug Smythies April 1, 2021, 11:27 p.m. UTC | #1
Hi Pratik,

On Thu, Apr 1, 2021 at 4:45 AM Pratik Rajesh Sampat
<psampat@linux.ibm.com> wrote:
>
...

> To run this test specifically:
> $ make -C tools/testing/selftests TARGETS="cpuidle" run_tests

I have not become any smarter than I was with version 1,
and still assumed that the "$" meant regular user.
Please put it as "#" or separate the two steps, compile and run.

>
> There are a few optinal arguments too that the script can take

optional

Suggest to also specifically mention how to run without re-compile,

# ./cpuidle.sh -v

Note also that the test still leaves all idle states disabled when done.

>         [-h <help>]
>         [-i <run timer tests>]
>         [-m <location of the module>]
>         [-o <location of the output>]
>         [-v <verbose> (run on all cpus)]
> Default Output location in: tools/testing/selftest/cpuidle/cpuidle.log

...

> +cpu_is_online()
> +{
> +       cpu=$1
> +       if [ ! -f "/sys/devices/system/cpu/cpu$cpu/online" ]; then
> +               echo 0

incorrect. should be:

> +               echo 1

... Doug
Pratik R. Sampat April 4, 2021, 7:34 a.m. UTC | #2
Hello Doug,

Thanks for your review.

On 02/04/21 4:57 am, Doug Smythies wrote:
> Hi Pratik,
>
> On Thu, Apr 1, 2021 at 4:45 AM Pratik Rajesh Sampat
> <psampat@linux.ibm.com> wrote:
> ...
>
>> To run this test specifically:
>> $ make -C tools/testing/selftests TARGETS="cpuidle" run_tests
> I have not become any smarter than I was with version 1,
> and still assumed that the "$" meant regular user.
> Please put it as "#" or separate the two steps, compile and run.

Apologies, I missed incorporating the root user discussion we had.
I'll add a sudo past the "$" symbol.

>> There are a few optinal arguments too that the script can take
> optional
>
> Suggest to also specifically mention how to run without re-compile,
>
> # ./cpuidle.sh -v

Sure thing, I'll add a comment specifying this.

> Note also that the test still leaves all idle states disabled when done.

Yes, I missed out enabling all the idle states after the tests are done.
I'll spin a new version where I enable idle states at the end of the experiment
so that the system stays coherent.

>>          [-h <help>]
>>          [-i <run timer tests>]
>>          [-m <location of the module>]
>>          [-o <location of the output>]
>>          [-v <verbose> (run on all cpus)]
>> Default Output location in: tools/testing/selftest/cpuidle/cpuidle.log
> ...
>
>> +cpu_is_online()
>> +{
>> +       cpu=$1
>> +       if [ ! -f "/sys/devices/system/cpu/cpu$cpu/online" ]; then
>> +               echo 0
> incorrect. should be:
>
>> +               echo 1

Right! Thanks for catching this.

> ... Doug

Thank you,
Pratik
diff mbox series

Patch

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 6c575cf34a71..561eb67a4839 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -7,6 +7,7 @@  TARGETS += cgroup
 TARGETS += clone3
 TARGETS += core
 TARGETS += cpufreq
+TARGETS += cpuidle
 TARGETS += cpu-hotplug
 TARGETS += drivers/dma-buf
 TARGETS += efivarfs
diff --git a/tools/testing/selftests/cpuidle/Makefile b/tools/testing/selftests/cpuidle/Makefile
new file mode 100644
index 000000000000..cbe13feced34
--- /dev/null
+++ b/tools/testing/selftests/cpuidle/Makefile
@@ -0,0 +1,6 @@ 
+# SPDX-License-Identifier: GPL-2.0
+all:
+
+TEST_PROGS := cpuidle.sh
+
+include ../lib.mk
\ No newline at end of file
diff --git a/tools/testing/selftests/cpuidle/cpuidle.sh b/tools/testing/selftests/cpuidle/cpuidle.sh
new file mode 100755
index 000000000000..468112285900
--- /dev/null
+++ b/tools/testing/selftests/cpuidle/cpuidle.sh
@@ -0,0 +1,323 @@ 
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+LOG=cpuidle.log
+MODULE=/lib/modules/$(uname -r)/kernel/drivers/cpuidle/test-cpuidle_latency.ko
+
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+
+SMT=$(lscpu | grep "Thread(s) per core" | awk '{print $4}')
+RUN_TIMER_TEST=0
+
+helpme()
+{
+	printf "Usage: $0 [-h] [-todg args]
+	[-h <help>]
+	[-i <run timer tests>]
+	[-m <location of the module>]
+	[-o <location of the output>]
+	[-v <verbose>]
+	\n"
+	exit 2
+}
+
+parse_arguments()
+{
+	while getopts ht:m:o:vt:it: arg
+	do
+		case $arg in
+			h) # --help
+				helpme
+				;;
+			i) # run timer tests
+				RUN_TIMER_TEST=1
+				;;
+			m) # --mod-file
+				MODULE=$OPTARG
+				;;
+			o) # output log files
+				LOG=$OPTARG
+				;;
+			v) # Verbose mode
+				SMT=1
+				;;
+			\?)
+				helpme
+				;;
+		esac
+	done
+}
+
+ins_mod()
+{
+	debugfs_file=/sys/kernel/debug/latency_test/ipi_latency_ns
+	# Check if the module is already loaded
+	if [ -f "$debugfs_file" ]; then
+		printf "Module already loaded\n\n"
+		return 0
+	fi
+	# Try to load the module
+	if [ ! -f "$MODULE" ]; then
+		printf "$MODULE module does not exist. Exitting\n"
+		exit $ksft_skip
+	fi
+	printf "Inserting $MODULE module\n\n"
+	insmod $MODULE
+	if [ $? != 0 ]; then
+		printf "Insmod $MODULE failed\n"
+		exit $ksft_skip
+	fi
+}
+
+compute_average()
+{
+	arr=("$@")
+	sum=0
+	size=${#arr[@]}
+	if [ $size == 0 ]; then
+		avg=0
+		return 1
+	fi
+	for i in "${arr[@]}"
+	do
+		sum=$((sum + i))
+	done
+	avg=$((sum/size))
+}
+
+# Disable all stop states
+disable_idle()
+{
+	for ((cpu=0; cpu<NUM_CPUS; cpu++))
+	do
+		local cpu_status=$(cpu_is_online $cpu)
+		if [ $cpu_status == 0 ]; then
+			continue
+		fi
+		for ((state=0; state<NUM_STATES; state++))
+		do
+			echo 1 > /sys/devices/system/cpu/cpu$cpu/cpuidle/state$state/disable
+		done
+	done
+}
+
+# Perform operation on each CPU for the given state
+# $1 - Operation: enable (0) / disable (1)
+# $2 - State to enable
+op_state()
+{
+	for ((cpu=0; cpu<NUM_CPUS; cpu++))
+	do
+		local cpu_status=$(cpu_is_online $cpu)
+		if [ $cpu_status == 0 ]; then
+			continue
+		fi
+		echo $1 > /sys/devices/system/cpu/cpu$cpu/cpuidle/state$2/disable
+	done
+}
+
+cpuidle_enable_state()
+{
+	state=$1
+	op_state 0 $state
+}
+
+cpuidle_disable_state()
+{
+	state=$1
+	op_state 1 $state
+}
+
+cpu_is_online()
+{
+	cpu=$1
+	if [ ! -f "/sys/devices/system/cpu/cpu$cpu/online" ]; then
+		echo 0
+		return
+	fi
+	status=$(cat /sys/devices/system/cpu/cpu$cpu/online)
+	echo $status
+}
+
+# Extract latency in microseconds and convert to nanoseconds
+extract_latency()
+{
+	for ((state=0; state<NUM_STATES; state++))
+	do
+		latency=$(($(cat /sys/devices/system/cpu/cpu0/cpuidle/state$state/latency) * 1000))
+		latency_arr+=($latency)
+	done
+}
+
+# Run the IPI test
+# $1 run for baseline - busy cpu or regular environment
+# $2 destination cpu
+ipi_test_once()
+{
+	dest_cpu=$2
+	if [ "$1" = "baseline" ]; then
+		# Keep the CPU busy
+		taskset -c $dest_cpu cat /dev/random > /dev/null &
+		task_pid=$!
+		# Wait for the workload to achieve 100% CPU usage
+		sleep 1
+	fi
+	taskset 0x1 echo $dest_cpu > /sys/kernel/debug/latency_test/ipi_cpu_dest
+	ipi_latency=$(cat /sys/kernel/debug/latency_test/ipi_latency_ns)
+	src_cpu=$(cat /sys/kernel/debug/latency_test/ipi_cpu_src)
+	if [ "$1" = "baseline" ]; then
+		kill $task_pid
+		wait $task_pid 2>/dev/null
+	fi
+}
+
+# Incrementally Enable idle states one by one and compute the latency
+run_ipi_tests()
+{
+	extract_latency
+	disable_idle
+	declare -a avg_arr
+	echo -e "--IPI Latency Test---" | tee -a $LOG
+
+	echo -e "--Baseline IPI Latency measurement: CPU Busy--" >> $LOG
+	printf "%s %10s %12s\n" "SRC_CPU" "DEST_CPU" "IPI_Latency(ns)" >> $LOG
+	for ((cpu=0; cpu<NUM_CPUS; cpu+=SMT))
+	do
+		local cpu_status=$(cpu_is_online $cpu)
+		if [ $cpu_status == 0 ]; then
+			continue
+		fi
+		ipi_test_once "baseline" $cpu
+		printf "%-3s %10s %12s\n" $src_cpu $cpu $ipi_latency >> $LOG
+		avg_arr+=($ipi_latency)
+	done
+	compute_average "${avg_arr[@]}"
+	echo -e "Baseline Avg IPI latency(ns): $avg" | tee -a $LOG
+
+	for ((state=0; state<NUM_STATES; state++))
+	do
+		unset avg_arr
+		echo -e "---Enabling state: $state---" >> $LOG
+		cpuidle_enable_state $state
+		printf "%s %10s %12s\n" "SRC_CPU" "DEST_CPU" "IPI_Latency(ns)" >> $LOG
+		for ((cpu=0; cpu<NUM_CPUS; cpu+=SMT))
+		do
+			local cpu_status=$(cpu_is_online $cpu)
+			if [ $cpu_status == 0 ]; then
+				continue
+			fi
+			# Running IPI test and logging results
+			sleep 1
+			ipi_test_once "test" $cpu
+			printf "%-3s %10s %12s\n" $src_cpu $cpu $ipi_latency >> $LOG
+			avg_arr+=($ipi_latency)
+		done
+		compute_average "${avg_arr[@]}"
+		echo -e "Expected IPI latency(ns): ${latency_arr[$state]}" >> $LOG
+		echo -e "Observed Avg IPI latency(ns) - State $state: $avg" | tee -a $LOG
+		cpuidle_disable_state $state
+	done
+}
+
+# Extract the residency in microseconds and convert to nanoseconds.
+# Add 100 ns so that the timer stays for a little longer than the residency
+extract_residency()
+{
+	for ((state=0; state<NUM_STATES; state++))
+	do
+		residency=$(($(cat /sys/devices/system/cpu/cpu0/cpuidle/state$state/residency) * 1000 + 200))
+		residency_arr+=($residency)
+	done
+}
+
+# Run the Timeout test
+# $1 run for baseline - busy cpu or regular environment
+# $2 destination cpu
+# $3 timeout
+timeout_test_once()
+{
+	dest_cpu=$2
+	if [ "$1" = "baseline" ]; then
+		# Keep the CPU busy
+		taskset -c $dest_cpu cat /dev/random > /dev/null &
+		task_pid=$!
+		# Wait for the workload to achieve 100% CPU usage
+		sleep 1
+	fi
+	taskset -c $dest_cpu echo $3 > /sys/kernel/debug/latency_test/timeout_expected_ns
+	# Wait for the result to populate
+	sleep 0.1
+	timeout_diff=$(cat /sys/kernel/debug/latency_test/timeout_diff_ns)
+	src_cpu=$(cat /sys/kernel/debug/latency_test/timeout_cpu_src)
+	if [ "$1" = "baseline" ]; then
+		kill $task_pid
+		wait $task_pid 2>/dev/null
+	fi
+}
+
+run_timeout_tests()
+{
+	extract_residency
+	disable_idle
+	declare -a avg_arr
+	echo -e "\n--Timeout Latency Test--" | tee -a $LOG
+
+	echo -e "--Baseline Timeout Latency measurement: CPU Busy--" >> $LOG
+	printf "%s %10s %10s\n" "Wakeup_src" "Baseline_delay(ns)">> $LOG
+	for ((cpu=0; cpu<NUM_CPUS; cpu+=SMT))
+	do
+		local cpu_status=$(cpu_is_online $cpu)
+		if [ $cpu_status == 0 ]; then
+			continue
+		fi
+		timeout_test_once "baseline" $cpu 1000000
+		printf "%-3s %13s\n" $src_cpu $timeout_diff >> $LOG
+		avg_arr+=($timeout_diff)
+	done
+	compute_average "${avg_arr[@]}"
+	echo -e "Baseline Avg timeout diff(ns): $avg" | tee -a $LOG
+
+	for ((state=0; state<NUM_STATES; state++))
+	do
+		unset avg_arr
+		echo -e "---Enabling state: $state---" >> $LOG
+		cpuidle_enable_state $state
+		printf "%s %10s %10s\n" "Wakeup_src" "Baseline_delay(ns)" "Delay(ns)" >> $LOG
+		for ((cpu=0; cpu<NUM_CPUS; cpu+=SMT))
+		do
+			local cpu_status=$(cpu_is_online $cpu)
+			if [ $cpu_status == 0 ]; then
+				continue
+			fi
+			timeout_test_once "test" $cpu 1000000
+			printf "%-3s %13s %18s\n" $src_cpu $baseline_timeout_diff $timeout_diff >> $LOG
+			avg_arr+=($timeout_diff)
+		done
+		compute_average "${avg_arr[@]}"
+		echo -e "Expected timeout(ns): ${residency_arr[$state]}" >> $LOG
+		echo -e "Observed Avg timeout diff(ns) - State $state: $avg" | tee -a $LOG
+		cpuidle_disable_state $state
+	done
+}
+
+declare -a residency_arr
+declare -a latency_arr
+
+parse_arguments $@
+
+rm -f $LOG
+touch $LOG
+NUM_CPUS=$(nproc --all)
+NUM_STATES=$(ls -1 /sys/devices/system/cpu/cpu0/cpuidle/ | wc -l)
+
+ins_mod $MODULE
+
+run_ipi_tests
+if [ $RUN_TIMER_TEST == 1 ]; then
+	run_timeout_tests
+fi
+
+printf "Removing $MODULE module\n"
+printf "Full Output logged at: $LOG\n"
+rmmod $MODULE
diff --git a/tools/testing/selftests/cpuidle/settings b/tools/testing/selftests/cpuidle/settings
new file mode 100644
index 000000000000..a26c38a70d77
--- /dev/null
+++ b/tools/testing/selftests/cpuidle/settings
@@ -0,0 +1,2 @@ 
+timeout=0
+