Re: [PATCH] perf/test: fix perf ftrace test on s390
From: Sven Schnelle
Date: Fri Nov 08 2024 - 01:28:37 EST
Namhyung Kim <namhyung@xxxxxxxxxx> writes:
> 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.
The ftrace profile test failed, because the ring buffer was not large
enough, and some lines (especially the interesting ones with nanosleep
in it) where dropped.
>
>> 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.
Ok, thanks. I leave it to Thomas to decide whether he wants to add this
option to the CI run.
Thanks!