linux-kernel - Re: [PATCH] perf test arm-spe: Check if perf-record hangs when recording workload with forks

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Date:   Fri, 13 May 2022 14:03:52 +0100
From:   James Clark <james.clark@....com>
To:     German Gomez <german.gomez@....com>, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org, acme@...nel.org
Cc:     Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>
Subject: Re: [PATCH] perf test arm-spe: Check if perf-record hangs when
 recording workload with forks



On 28/02/2022 16:56, German Gomez wrote:
> Add shell test to check if perf-record hangs when recording an arm_spe
> event with forks.
> 
> The test FAILS if the Kernel is not patched with Commit 961c391217 ("perf:
> Always wake the parent event").
> 
> Unpatched Kernel:
> 
>   $ perf test -v 90
>   90: Check Arm SPE doesn't hang when there are forks
>   --- start ---
>   test child forked, pid 14232
>   Recording workload with fork
>   Log lines = 90 /tmp/__perf_test.stderr.0Nu0U
>   Log lines after 1 second = 90 /tmp/__perf_test.stderr.0Nu0U
>   SPE hang test: FAIL
>   test child finished with -1
>   ---- end ----
>   Check Arm SPE trace data in workload with forks: FAILED!
> 
> Patched Kernel:
> 
>   $ perf test -v 90
>   90: Check Arm SPE doesn't hang when there are forks
>   --- start ---
>   test child forked, pid 2930
>   Compiling test program...
>   Recording workload...
>   Log lines = 478 /tmp/__perf_test.log.026AI
>   Log lines after 1 second = 557 /tmp/__perf_test.log.026AI
>   SPE hang test: PASS
>   Cleaning up files...
>   test child finished with 0
>   ---- end ----
>   Check Arm SPE trace data in workload with forks: Ok
> 
> Signed-off-by: German Gomez <german.gomez@....com>

Reviewed-by: James Clark <james.clark@....com>

> ---
>  tools/perf/tests/shell/test_arm_spe_fork.sh | 92 +++++++++++++++++++++
>  1 file changed, 92 insertions(+)
>  create mode 100755 tools/perf/tests/shell/test_arm_spe_fork.sh
> 
> diff --git a/tools/perf/tests/shell/test_arm_spe_fork.sh b/tools/perf/tests/shell/test_arm_spe_fork.sh
> new file mode 100755
> index 000000000..c920d3583
> --- /dev/null
> +++ b/tools/perf/tests/shell/test_arm_spe_fork.sh
> @@ -0,0 +1,92 @@
> +#!/bin/sh
> +# Check Arm SPE doesn't hang when there are forks
> +
> +# SPDX-License-Identifier: GPL-2.0
> +# German Gomez <german.gomez@....com>, 2022
> +
> +skip_if_no_arm_spe_event() {
> +	perf list | egrep -q 'arm_spe_[0-9]+//' && return 0
> +	return 2
> +}
> +
> +skip_if_no_arm_spe_event || exit 2
> +
> +# skip if there's no compiler
> +if ! [ -x "$(command -v cc)" ]; then
> +	echo "failed: no compiler, install gcc"
> +	exit 2
> +fi
> +
> +TEST_PROGRAM_SOURCE=$(mktemp /tmp/__perf_test.program.XXXXX.c)
> +TEST_PROGRAM=$(mktemp /tmp/__perf_test.program.XXXXX)
> +PERF_DATA=$(mktemp /tmp/__perf_test.perf.data.XXXXX)
> +PERF_RECORD_LOG=$(mktemp /tmp/__perf_test.log.XXXXX)
> +
> +cleanup_files()
> +{
> +	echo "Cleaning up files..."
> +	rm -f ${PERF_RECORD_LOG}
> +	rm -f ${PERF_DATA}
> +	rm -f ${TEST_PROGRAM_SOURCE}
> +	rm -f ${TEST_PROGRAM}
> +}
> +
> +trap cleanup_files exit term int
> +
> +# compile test program
> +cat << EOF > $TEST_PROGRAM_SOURCE
> +#include <math.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <unistd.h>
> +#include <sys/wait.h>
> +
> +int workload() {
> +  while (1)
> +    sqrt(rand());
> +  return 0;
> +}
> +
> +int main() {
> +  switch (fork()) {
> +    case 0:
> +      return workload();
> +    case -1:
> +      return 1;
> +    default:
> +      wait(NULL);
> +  }
> +  return 0;
> +}
> +EOF
> +
> +echo "Compiling test program..."
> +CFLAGS="-lm"
> +cc $TEST_PROGRAM_SOURCE $CFLAGS -o $TEST_PROGRAM || exit 1
> +
> +echo "Recording workload..."
> +perf record -o ${PERF_DATA} -e arm_spe/period=65536/ -vvv -- $TEST_PROGRAM > ${PERF_RECORD_LOG} 2>&1 &
> +PERFPID=$!
> +
> +# Check if perf hangs by checking the perf-record logs.
> +sleep 1
> +log0=$(wc -l $PERF_RECORD_LOG)
> +echo Log lines = $log0
> +sleep 1
> +log1=$(wc -l $PERF_RECORD_LOG)
> +echo Log lines after 1 second = $log1
> +
> +kill $PERFPID
> +wait $PERFPID
> +# test program may leave an orphan process running the workload
> +killall $(basename $TEST_PROGRAM)
> +
> +if [ "$log0" = "$log1" ];
> +then
> +        echo "SPE hang test: FAIL"
> +        exit 1
> +else
> +        echo "SPE hang test: PASS"
> +fi
> +
> +exit 0