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

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Date:	Mon, 27 Oct 2008 14:06:30 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	fche@...hat.com (Frank Ch. Eigler)
Cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Steven Rostedt <rostedt@...dmis.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>, lenb@...nel.org
Subject: Re: PATCH] ftrace: Add a C/P state tracer to help power
 optimization

On Mon, 27 Oct 2008 15:47:30 -0400
fche@...hat.com (Frank Ch. Eigler) wrote:

> 
> Arjan van de Ven <arjan@...radead.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....


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
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