Re: PATCH] ftrace: Add a C/P state tracer to help power optimization

[Ingo Molnar <mingo@elte.hu>]

* Arjan van de Ven <arjan@infradead.org> wrote:

> On Mon, 27 Oct 2008 15:47:30 -0400
> fche@redhat.com (Frank Ch. Eigler) wrote:
> 
> > 
> > Arjan van de Ven <arjan@infradead.org> writes:
> > 
> > > [...]
> > > --- a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
> > > +++ b/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
> > > [...]
> > > @@ -427,6 +429,8 @@ static int acpi_cpufreq_target(struct
> > > cpufreq_policy *policy, }
> > >  	}
> > >  
> > > +	trace_power_mark(&it, POWER_PSTATE, next_perf_state);
> > > +
> > >  	switch (data->cpu_feature) {
> > >  	case SYSTEM_INTEL_MSR_CAPABLE:
> > >  		cmd.type = SYSTEM_INTEL_MSR_CAPABLE;
> > > [...]
> > 
> > Is there some reason that this doesn't use tracepoints instead
> > of such a single-backend hook?
> 
> because it's a ton simpler this way? do simple things simpe and all 
> that....

correct.

	Ingo