Re: [GIT PULL] adaptive spinning mutexes

Andrew Morton
2009-01-14T19:36:38Z

On Wed, 14 Jan 2009 20:00:08 +0100
Ingo Molnar <mingo@elte.hu> wrote:

>
> * Andrew Morton <akpm@linux-foundation.org> wrote:
>
> > On Wed, 14 Jan 2009 19:33:19 +0100 Ingo Molnar <mingo@elte.hu> wrote:
> >
> > > Please pull the adaptive-mutexes-for-linus git tree
> >
> > <fear>
> >
> > - It seems a major shortcoming that the feature is disabled if
> > CONFIG_DEBUG_MUTEXES=y. It means that lots of people won't test it.

^^^?

> > - When people hit performance/latency oddities, it would be nice if
> > they had a /proc knob with which they could disable this feature at
> > runtime.
> >
> > This would also be useful for comparative performance testing.
>
> Yeah. From my other mail:
>
> > > We still have the /sys/debug/sched_features tunable under
> > > CONFIG_SCHED_DEBUG=y, so should this cause any performance regressions
> > > somewhere, it can be pinned down and blamed back on this change
> > > easily, without bisection and without rebooting the box.
>
> This kind of easy knob was included early on - this is how all those spin
> versus no-spin numbers were done.

Do people enable CONFIG_SCHED_DEBUG?

CONFIG_DEBUG_MUTEXES=n, CONFIG_SCHED_DEBUG=y is getting to be a pretty
small subset?