linux-kernel - Re: [PATCH v2 1/1] perf test arm64: Test unwinding using fame-pointer (fp) mode

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Date:   Wed, 16 Mar 2022 17:48:50 +0000
From:   German Gomez <german.gomez@....com>
To:     James Clark <james.clark@....com>, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org, acme@...nel.org
Cc:     mark.rutland@....com, namhyung@...nel.org, leo.yan@...aro.org,
        Alexandre.Truong@....com, Jiri Olsa <jolsa@...nel.org>
Subject: Re: [PATCH v2 1/1] perf test arm64: Test unwinding using fame-pointer
 (fp) mode


On 16/03/2022 17:30, James Clark wrote:
>
> On 16/03/2022 17:20, German Gomez wrote:
>> Add a shell script to check that the call-graphs generated using frame
>> pointers (--call-graph fp) are complete and not missing leaf functions:
>>
>>   | $ perf test 88 -v
>>   |  88: Check Arm64 callgraphs are complete in fp mode                  :
>>   | --- start ---
>>   | test child forked, pid 8734
>>   |  + Compiling test program (/tmp/test_program.Cz3yL)...
>>   |  + Recording (PID=8749)...
>>   |  + Stopping perf-record...
>>   | test_program.Cz
>>   |                  728 leaf
>>   |                  753 parent
>>   |                  76c main
>>   | test child finished with 0
>>   | ---- end ----
>>   | Check Arm SPE callgraphs are complete in fp mode: Ok
>>
> Ran it on N1SDP and it passes, and it fails if b9f6fbb3b2c2 isn't applied.

I forgot to mention in the notes that it's supposed to work with both unwinders:

$ make                # for libunwind (default)
$ make NO_LIBUNWIND=1 # for libdw

>
> Reviewed-by: James Clark <james.clark@....com>
>
>> Fixes: b9f6fbb3b2c2 ("perf arm64: Inject missing frames when using 'perf record --call-graph=fp'")
>> Suggested-by: Jiri Olsa <jolsa@...nel.org>
>> Signed-off-by: German Gomez <german.gomez@....com>
>> ---
>> Changes since v1: https://lore.kernel.org/all/a6ba0ea8-f070-9f79-f018-f638ff677c7c@arm.com/
>>  - Add explicit '-g' flag to GCC command
>> ---
>>  .../perf/tests/shell/test_arm_callgraph_fp.sh | 68 +++++++++++++++++++
>>  1 file changed, 68 insertions(+)
>>  create mode 100755 tools/perf/tests/shell/test_arm_callgraph_fp.sh
>>
>> diff --git a/tools/perf/tests/shell/test_arm_callgraph_fp.sh b/tools/perf/tests/shell/test_arm_callgraph_fp.sh
>> new file mode 100755
>> index 000000000..ea1b4e6bb
>> --- /dev/null
>> +++ b/tools/perf/tests/shell/test_arm_callgraph_fp.sh
>> @@ -0,0 +1,68 @@
>> +#!/bin/sh
>> +# Check Arm64 callgraphs are complete in fp mode
>> +# SPDX-License-Identifier: GPL-2.0
>> +
>> +lscpu | grep -q "aarch64" || exit 2
>> +
>> +if ! [ -x "$(command -v cc)" ]; then
>> +	echo "failed: no compiler, install gcc"
>> +	exit 2
>> +fi
>> +
>> +PERF_DATA=$(mktemp /tmp/__perf_test.perf.data.XXXXX)
>> +TEST_PROGRAM_SOURCE=$(mktemp /tmp/test_program.XXXXX.c)
>> +TEST_PROGRAM=$(mktemp /tmp/test_program.XXXXX)
>> +
>> +cleanup_files()
>> +{
>> +	rm -f $PERF_DATA
>> +	rm -f $TEST_PROGRAM_SOURCE
>> +	rm -f $TEST_PROGRAM
>> +}
>> +
>> +trap cleanup_files exit term int
>> +
>> +cat << EOF > $TEST_PROGRAM_SOURCE
>> +int a = 0;
>> +void leaf(void) {
>> +  for (;;)
>> +    a += a;
>> +}
>> +void parent(void) {
>> +  leaf();
>> +}
>> +int main(void) {
>> +  parent();
>> +  return 0;
>> +}
>> +EOF
>> +
>> +echo " + Compiling test program ($TEST_PROGRAM)..."
>> +
>> +CFLAGS="-g -O0 -fno-inline -fno-omit-frame-pointer"
>> +cc $CFLAGS $TEST_PROGRAM_SOURCE -o $TEST_PROGRAM || exit 1
>> +
>> +# Add a 1 second delay to skip samples that are not in the leaf() function
>> +perf record -o $PERF_DATA --call-graph fp -e cycles//u -D 1000 -- $TEST_PROGRAM 2> /dev/null &
>> +PID=$!
>> +
>> +echo " + Recording (PID=$PID)..."
>> +sleep 2
>> +echo " + Stopping perf-record..."
>> +
>> +kill $PID
>> +wait $PID
>> +
>> +# expected perf-script output:
>> +#
>> +# program 
>> +# 	728 leaf
>> +# 	753 parent
>> +# 	76c main
>> +# ...
>> +
>> +perf script -i $PERF_DATA -F comm,ip,sym | head -n4
>> +perf script -i $PERF_DATA -F comm,ip,sym | head -n4 | \
>> +	awk '{ if ($2 != "") sym[i++] = $2 } END { if (sym[0] != "leaf" ||
>> +						       sym[1] != "parent" ||
>> +						       sym[2] != "main") exit 1 }'