linux-kernel - Re: [PATCH 2/2] x86 cpufreq: Make trace_power

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Date:	Fri, 30 Apr 2010 11:08:14 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Thomas Renninger <trenn@...e.de>
Cc:	x86@...nel.org, linux-trace-users@...r.kernel.org,
	linux-perf-users@...r.kernel.org, robert.schoene@...dresden.de,
	cpufreq@...r.kernel.org, linux-kernel@...r.kernel.org,
	davej@...hat.com, arjan@...radead.org,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Fr??d??ric Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 2/2] x86 cpufreq: Make trace_power_frequency cpufreq
 driver independent


* Thomas Renninger <trenn@...e.de> wrote:

> +		trace_power_start(POWER_CSTATE, 1, smp_processor_id());
> +	trace_power_start(POWER_CSTATE, (ax>>4)+1, smp_processor_id());
> +		trace_power_start(POWER_CSTATE, 1, smp_processor_id());
> +	trace_power_start(POWER_CSTATE, 0, smp_processor_id());
> +                trace_power_frequency(POWER_PSTATE, freqs->new, freqs->cpu);
> +	trace_power_end(smp_processor_id());

Extending power tracing to all cpufreq modules is obviously a good thing.

But why is trace_power_start() adding a CPU ID argument? CPU ids are already 
available and can be sampled via PERF_SAMPLE_CPU if needed. AFAICS only 
power_frequency needs a new 'target_cpu_id' field.

> diff --git a/tools/perf/builtin-timechart.c b/tools/perf/builtin-timechart.c
> index 0d4d8ff..7809bef 100644
> --- a/tools/perf/builtin-timechart.c
> +++ b/tools/perf/builtin-timechart.c

Timechart is maintained by Arjan so we need an ack from him as well. I've seen 
some back and forth in the discussions - what's the technical resolution of 
that?

(Also, there's some whitespace noise in the patch.)

Thanks,

	Ingo
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