Re: [PATCH v2 2/2] selftest/cpuidle: Add support for cpuidle latency measurement

Hi Gautham, Thanks for the review.


On 20/07/20 11:22 am, Gautham R Shenoy wrote:

Hi Pratik,


On Fri, Jul 17, 2020 at 02:48:01PM +0530, Pratik Rajesh Sampat wrote:

quoted

This patch adds support to trace IPI based and timer based wakeup
latency from idle states

Latches onto the test-cpuidle_latency kernel module using the debugfs
interface to send IPIs or schedule a timer based event, which in-turn
populates the debugfs with the latency measurements.

Currently for the IPI and timer tests; first disable all idle states
and then test for latency measurements incrementally enabling each state

Signed-off-by: Pratik Rajesh Sampat <redacted>

A few comments below.

quoted

---
  tools/testing/selftests/Makefile           |   1 +
  tools/testing/selftests/cpuidle/Makefile   |   6 +
  tools/testing/selftests/cpuidle/cpuidle.sh | 257 +++++++++++++++++++++
  tools/testing/selftests/cpuidle/settings   |   1 +
  4 files changed, 265 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

[..skip..]

quoted

+
+ins_mod()
+{
+	if [ ! -f "$MODULE" ]; then
+		printf "$MODULE module does not exist. Exitting\n"

If the module has been compiled into the kernel (due to a
localyesconfig, for instance), then it is unlikely that we will find
it in /lib/modules. Perhaps you want to check if the debugfs
directories created by the module exist, and if so, print a message
saying that the modules is already loaded or some such?

That's a good idea. I can can grep for this module within /proc/modules
and not insert it, if it is already there

quoted

+		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=${#arr[@]}
+	for i in "${arr[@]}"
+	do
+		sum=$((sum + i))
+	done
+	avg=$((sum/size))

It would be good to assert that "size" isn't 0 here.

Sure

quoted

+}
+
+# Disable all stop states
+disable_idle()
+{
+	for ((cpu=0; cpu<NUM_CPUS; cpu++))
+	do
+		for ((state=0; state<NUM_STATES; state++))
+		do
+			echo 1 > /sys/devices/system/cpu/cpu$cpu/cpuidle/state$state/disable

So, on offlined CPUs, we won't see
/sys/devices/system/cpu/cpu$cpu/cpuidle/state$state directory. You
should probably perform this operation only on online CPUs.

Right. I should make CPU operations only on online CPUs all over the script

[..snip..]

Thanks
Pratik