Re: [GIT PULL] adaptive spinning mutexes

Ingo Molnar
2009-01-14T20:51:22Z

* Andrew Morton <akpm@linux-foundation.org> wrote:

> > > Do people enable CONFIG_SCHED_DEBUG?
> >
> > If they suspect performance problems and want to analyze them?
>
> The vast majority of users do not and usually cannot compile their own
> kernels.

... which they derive from distro kernels or some old .config they always
used, via 'make oldconfig'. You are arguing against well-established facts
here.

If you dont believe my word for it, here's an analysis of all kernel
configs posted to lkml in the past 8 months:

$ grep ^CONFIG_SCHED_DEBUG linux-kernel | wc -l
424

$ grep 'CONFIG_SCHED_DEBUG is not' linux-kernel | wc -l
109

i.e. CONFIG_SCHED_DEBUG=y is set in 80% of the configs. A large majority
of testers has it enabled and /sys/debug/sched_features was always a good
mechanism that we used for runtime toggles.

> > Note that CONFIG_SCHED_DEBUG=y is also the default.
>
> akpm:/usr/src/25> echo $ARCH
> x86_64
> akpm:/usr/src/25> make defconfig
> *** Default configuration is based on 'x86_64_defconfig'

x86 defconfig is used too, but it's a pretty rare usage.

Under default i mean the customary meaning of default config: it's the
default if you come via 'make oldconfig' or if you derive your config from
a distro config:

| config SCHED_DEBUG
| bool "Collect scheduler debugging info"
| depends on DEBUG_KERNEL && PROC_FS
| default y

Ingo