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

[Shuah Khan]

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@xxxxxxxxxx>
>   
> > Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
> > ---
> >   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