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

[Pratik Sampat]

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:
> > 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 <psampat@xxxxxxxxxxxxx>
> A few comments below.
>
> > ---
> >   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..]
>
> > +
> > +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

> > +		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

> > +}
> > +
> > +# 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