Re: [LTP] [PATCH V3] lib: multiply the max_runtime if detect slow kconfigs

Petr Vorel
2024-12-16T12:29:16Z

Hi Li,

...
> > > +/*
> > > + * List of kernel config options that may degrade performance when
> > enabled.
> > > + */
> > > +static struct tst_kconfig_var slow_kconfigs[] = {
> > > + TST_KCONFIG_INIT("CONFIG_PROVE_LOCKING"),
> > > + TST_KCONFIG_INIT("CONFIG_LOCKDEP"),
> > > + TST_KCONFIG_INIT("CONFIG_DEBUG_SPINLOCK"),
> > > + TST_KCONFIG_INIT("CONFIG_DEBUG_RT_MUTEXES"),
> > > + TST_KCONFIG_INIT("CONFIG_DEBUG_MUTEXES"),
> > > + TST_KCONFIG_INIT("CONFIG_DEBUG_PAGEALLOC"),
> > Does CONFIG_DEBUG_PAGEALLOC itself prolong the run? Isn't it that only when
> > debug_guardpage_minorder=... or debug_pagealloc=... is set?

> Good catch.

> I guess that won't impact the kernel performance if not set any
> of the parameters, because from the doc it is disabled by default.

> "When CONFIG_DEBUG_PAGEALLOC is set, this parameter
> enables the feature at boot time. In default, it is disabled.
> ....
> if we don't enable it at boot time and the the system will work
> mostly same with the kernel built without CONFIG_DEBUG_PAGEALLOC."

> So I would like to remove CONFIG_DEBUG_PAGEALLOC from
> the detecting.

Or maybe to detect if debug_pagealloc kernel cmdline is set with tst_kcmdline_parse()?

OTOH we run with debug_pagealloc=on only syscalls and some long running tests
(e.g. bind06) are even slightly faster than when running without it. But that
may be affected by QEMU host. Therefore let's skip CONFIG_DEBUG_PAGEALLOC until
I find a time to test how it affects the runtime.

> > https://www.kernel.org/doc/html/v5.2/admin-guide/kernel-parameters.html

> > I would need to run the test with these to see the difference.

> Any new found?

I'm sorry I haven't tested yet. Feel free to not to wait and merge. I'll try to
do it soon.

Kind regards,
Petr

> > > + TST_KCONFIG_INIT("CONFIG_KASAN"),
> > > + TST_KCONFIG_INIT("CONFIG_SLUB_RCU_DEBUG"),
> > > + TST_KCONFIG_INIT("CONFIG_TRACE_IRQFLAGS"),
> > > + TST_KCONFIG_INIT("CONFIG_LATENCYTOP"),
> > > + TST_KCONFIG_INIT("CONFIG_DEBUG_NET"),
> > > + TST_KCONFIG_INIT("CONFIG_EXT4_DEBUG"),
> > > + TST_KCONFIG_INIT("CONFIG_QUOTA_DEBUG"),
> > > + TST_KCONFIG_INIT("CONFIG_FAULT_INJECTION"),
> > > + TST_KCONFIG_INIT("CONFIG_DEBUG_OBJECTS")
> > > +};
> > > +
> > > +int tst_has_slow_kconfig(void)
> > > +{
> > > + unsigned int i;
> > > +
> > > + tst_kconfig_read(slow_kconfigs, ARRAY_SIZE(slow_kconfigs));
> > > +
> > Maybe here TINFO message "checking for options which slow the execution?
> > Or print it (once) only if option detected? Because it's not obvious why
> > we are
> > detecting it. Or after searching print what we did (4x prolonged runtime).

> Agree, the rest comments all look good.

+1

Kind regards,
Petr