Date:   Mon, 7 Sep 2020 21:06:24 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Suzuki K Poulose <suzuki.poulose@....com>
Cc:     acme@...nel.org, mathieu.poirier@...aro.org, mike.leach@...aro.org,
        peterz@...radead.org, mingo@...hat.com, mark.rutland@....com,
        alexander.shishkin@...ux.intel.com, jolsa@...hat.com,
        namhyung@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6] perf test: Introduce script for Arm CoreSight testing

Hi Suzuki,

On Mon, Sep 07, 2020 at 11:50:10AM +0100, Suzuki Kuruppassery Poulose wrote:
> On 09/07/2020 08:29 AM, Leo Yan wrote:
> > We need a simple method to test Perf with Arm CoreSight drivers, this
> > could be used for smoke testing when new patch is coming for perf or
> > CoreSight drivers, and we also can use the test to confirm if the
> > CoreSight has been enabled successfully on new platforms.
> > 
> > This patch introduces the shell script test_arm_coresight.sh which is
> > under the 'pert test' framework.  This script provides three testing
> > scenarios:
> > 
> > Test scenario 1: traverse all possible paths between source and sink
> > 
> > For traversing possible paths, simply to say, the testing rationale
> > is source oriented testing, it traverses every source (now only refers
> > to ETM device) and test its all possible sinks.  To search the complete
> > paths from one specific source to its sinks, this patch relies on the
> > sysfs '/sys/bus/coresight/devices/devX/out:Y' for depth-first search
> > (DFS) for iteration connected device nodes, if the output device is
> > detected as a sink device (the script will exclude TPIU device which can
> > not be supported for perf PMU), then it will test trace data recording
> > and decoding for it.
> > 
> > The script runs three output testings for every trace data:
> > - Test branch samples dumping with 'perf script' command;
> > - Test branch samples reporting with 'perf report' command;
> > - Use option '--itrace=i1000i' to insert synthesized instructions events
> >    and the script will check if perf can output the percentage value
> >    successfully based on the instruction samples.
> > 
> > Test scenario 2: system-wide test
> > 
> > For system-wide testing, it passes option '-a' to perf tool to enable
> > tracing on all CPUs, so it's hard to say which program will be traced.
> > But perf tool itself contributes much overload in this case, so it will
> > parse trace data and check if process 'perf' can be detected or not.
> > 
> > Test scenario 3: snapshot mode test.
> > 
> > For snapshot mode testing, it uses 'dd' command to launch a long running
> > program, so this can give chance to send signal -USR2; it will check the
> > captured trace data contains 'dd' related thread info or not.
> > 
> > If any test fails, it will report failure and directly exit with error.
> > This test will be only applied on a platform with PMU event 'cs_etm//',
> > otherwise will skip the testing.
> > 
> > Below is detailed usage for it:
> > 
> >    # cd $linux/tools/perf  -> This is important so can use shell script
> >    # perf test list
> >      [...]
> >      70: probe libc's inet_pton & backtrace it with ping
> >      71: Check Arm CoreSight trace data recording and synthesized samples
> >      72: Check open filename arg using perf trace + vfs_getname
> >      73: Zstd perf.data compression/decompression
> >      74: Add vfs_getname probe to get syscall args filenames
> >      75: Use vfs_getname probe to get syscall args filenames
> > 
> >    # perf test 71
> >      66: Check Arm CoreSight trace data recording and branch samples: Ok
> > 
> > Signed-off-by: Leo Yan <leo.yan@...aro.org>
> > ---
> > 
> > Changes in v6:
> > - Fixed indentation for arm_cs_iterate_devices() (Mathieu);
> > - Changed to remove ${perfdata} and ${file} for failure cases (Mathieu);
> > - Changed test name from "... branch samples" to "... synthesized samples".
> 
> minor nit: Instead of spilling the cleanup of the files allover the
> tests, could we use trap ... exit to cleanup ?
> 
> i.e,
> 
> cleanup_files()
> {
> 	# Cleanups here
> 	# rm -f ....
> }
> 
> trap cleanup_files exit

This and below suggestions are good for me, have followed them to respin
patch v7 and sent out for review.

Thanks a lot for reviewing and suggestions!

Leo

> > +arm_cs_iterate_devices() {
> > +	for dev in $1/connections/out\:*; do
> > +
> > +		# Skip testing if it's not a directory
> > +		! [ -d $dev ] && continue;
> > +
> > +		# Read out its symbol link file name
> > +		path=`readlink -f $dev`
> > +
> > +		# Extract device name from path, e.g.
> > +		#   path = '/sys/devices/platform/20010000.etf/tmc_etf0'
> > +		#     `> device_name = 'tmc_etf0'
> > +		device_name=`echo $path | awk -F/ '{print $(NF)}'`
> 
> Couldn't this be :
> 		device_name=$(basename $path) ?
> 
> 
> > +
> > +
> 
>  --- Cut here ---
> > +		# If the node of "enable_sink" is existed under the device path, this
> > +		# means the device is a sink device.  Need to exclude 'tpiu' since it
> > +		# cannot support perf PMU.
> > +		echo $device_name | egrep -q -v "tpiu"
> > +		if [ $? -eq 0 -a -e "$path/enable_sink" ]; then
> > +
> > +			pmu_dev="/sys/bus/event_source/devices/cs_etm/sinks/$device_name"
> > +
> > +			# Exit if the sink device is supported by PMU or not
> > +			if ! [ -f $pmu_dev ]; then
> > +				echo "PMU doesn't support $pmu_dev"
> > +				exit 1
> 
> This may not be fatal to the testing. Could be a warning and continue on
> to the next device ?
> 
> > +			fi
> 
> ---- Cut end ---
> 
> minor nit: Could this be moved into a function ? say, is_device_sink() ?
> 
> Rest looks fine to me.
> 
> Cheers
> Suzuki

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