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

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Date:	Mon, 27 Oct 2008 15:47:30 -0400
From:	fche@...hat.com (Frank Ch. Eigler)
To:	Arjan van de Ven <arjan@...radead.org>
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


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?


- FChE
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