Re: [PATCH] perf/test: fix perf ftrace test on s390

From: Namhyung Kim
Date: Thu Nov 07 2024 - 14:42:14 EST


On Thu, Nov 07, 2024 at 01:33:43PM +0100, Thomas Richter wrote:
> On s390 the perf test case ftrace sometimes fails as follows:
>
> # ./perf test ftrace
> 79: perf ftrace tests : FAILED!
> #
>
> The failure depends on the kernel .config file. Some configurarions
> always work fine, some do not.

Which test do you fail? ftrace trace or profile? I don't think it's
gonna be a problem for ftrace latency.


> To achieve success for all our tested kernel configurations, enlarge
> the buffer to store the traces complete without wrapping.
> The default buffer size is too small for all kernel configurations.
> Set the buffer size of /sys/kernel/tracing/buffer_size_kb to 16 MB

Actually you can use -m 16M option for perf ftrace trace and perf ftrace
profile. Then you don't need to care about restoring the original size.

Thanks,
Namhyung

>
> Output after:
> # ./perf test ftrace
> 79: perf ftrace tests : Ok
> #
>
> Signed-off-by: Thomas Richter <tmricht@xxxxxxxxxxxxx>
> Suggested-by: Sven Schnelle <svens@xxxxxxxxxxxxx>
> ---
> tools/perf/tests/shell/ftrace.sh | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/tools/perf/tests/shell/ftrace.sh b/tools/perf/tests/shell/ftrace.sh
> index a6ee740f0d7e..742d6b8f34d3 100755
> --- a/tools/perf/tests/shell/ftrace.sh
> +++ b/tools/perf/tests/shell/ftrace.sh
> @@ -80,10 +80,21 @@ test_ftrace_profile() {
> echo "perf ftrace profile test [Success]"
> }
>
> +if [ "$(uname -m)" = "s390x" ]
> +then
> + ftrace_size=$(cat /sys/kernel/tracing/buffer_size_kb)
> + echo 16384 > /sys/kernel/tracing/buffer_size_kb
> +fi
> +
> test_ftrace_list
> test_ftrace_trace
> test_ftrace_latency
> test_ftrace_profile
>
> +if [ "$(uname -m)" = "s390x" ]
> +then
> + echo $ftrace_size > /sys/kernel/tracing/buffer_size_kb
> +fi
> +
> cleanup
> exit 0
> --
> 2.47.0
>