linux-kernel - Re: [PATCH] selftests/cpufreq: Don't enable generic lock debugging options

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Message-ID: <703a435a-d448-360d-9344-8b8614a5cb5a@linuxfoundation.org>
Date:   Fri, 9 Jun 2023 12:52:22 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>,
        Mark Brown <broonie@...nel.org>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Shuah Khan <shuah@...nel.org>, linux-pm@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH] selftests/cpufreq: Don't enable generic lock debugging
 options

On 6/6/23 21:45, Viresh Kumar wrote:
> On 06-06-23, 15:11, Mark Brown wrote:
>> Currently the the config fragment for cpufreq enables a lot of generic
>> lock debugging.  While these options are useful when testing cpufreq
>> they aren't actually required to run the tests and are therefore out of
>> scope for the cpufreq fragement, they are more of a thing that it's good
>> to enable while doing testing than an actual requirement for cpufreq
>> testing specifically.  Having these debugging options enabled,
>> especially the mutex and spinlock instrumentation, mean that any build
>> that includes the cpufreq fragment is both very much larger than a
>> standard defconfig (eg, I'm seeing 35% on x86_64) and also slower at
>> runtime.
>>
>> This is causing real problems for CI systems.  In order to avoid
>> building large numbers of kernels they try to group kselftest fragments
>> together, frequently just grouping all the kselftest fragments into a
>> single block.  The increased size is an issue for memory constrained
>> systems and is also problematic for systems with fixed storage
>> allocations for kernel images (eg, typical u-boot systems) where it
>> frequently causes the kernel to overflow the storage space allocated for
>> kernels.  The reduced performance isn't too bad with real hardware but
>> can be disruptive on emulated platforms.
>>
>> In order to avoid these issues remove these generic instrumentation
>> options from the cpufreq fragment, bringing the cpufreq fragment into
>> line with other fragments which generally set requirements for testing
>> rather than nice to haves.
> 
> Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
>   
>> Signed-off-by: Mark Brown <broonie@...nel.org>
>> ---
>>   tools/testing/selftests/cpufreq/config | 8 --------
>>   1 file changed, 8 deletions(-)
>>
>> diff --git a/tools/testing/selftests/cpufreq/config b/tools/testing/selftests/cpufreq/config
>> index 75e900793e8a..ce5068f5a6a2 100644
>> --- a/tools/testing/selftests/cpufreq/config
>> +++ b/tools/testing/selftests/cpufreq/config
>> @@ -5,11 +5,3 @@ CONFIG_CPU_FREQ_GOV_USERSPACE=y
>>   CONFIG_CPU_FREQ_GOV_ONDEMAND=y
>>   CONFIG_CPU_FREQ_GOV_CONSERVATIVE=y
>>   CONFIG_CPU_FREQ_GOV_SCHEDUTIL=y
>> -CONFIG_DEBUG_RT_MUTEXES=y
>> -CONFIG_DEBUG_PLIST=y
>> -CONFIG_DEBUG_SPINLOCK=y
>> -CONFIG_DEBUG_MUTEXES=y
>> -CONFIG_DEBUG_LOCK_ALLOC=y
>> -CONFIG_PROVE_LOCKING=y
>> -CONFIG_LOCKDEP=y
>> -CONFIG_DEBUG_ATOMIC_SLEEP=y
> 
> FWIW, I enabled these earlier as cpufreq core had a history of races
> that are normally not caught without these enabled. But I think we
> have come a long way from that and these can be removed now.
> 

Thank you both. Applied to linux-kselftest next for Linux 6.5-rc1
This gives us time to ensure the above mentioned races are no
longer an issue.

thanks,
-- Shuah