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

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Message-ID: <20081004095257.41ba3703@infradead.org>
Date:	Sat, 4 Oct 2008 09:52:57 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	mingo@...e.hu, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ftrace: Add a C-state tracer to help power optimization

On Fri, 3 Oct 2008 20:32:51 -0400 (EDT)
Steven Rostedt <rostedt@...dmis.org> wrote:
> > +struct trace_cstate {
> > +	struct trace_entry	ent;
> > +	struct cstate_trace	state_data;
> > +};
> > +
> 
> Can you please register this in the trace_assign_type macro.
> 
> 	IF_ASSIGN(var, ent, struct trace_cstate, TRACE_BOOT); \

I don't see this anywhere in the kernel ;(

> And here, do not typecast. Use the trace_assign_type macro below.

nor that guy


> 
> > +	struct cstate_trace *it = &field->state_data;
> > +	struct trace_seq *s = &iter->seq;
> > +	struct timespec stamp = ktime_to_timespec(it->stamp);
> 
> Also note that iter->ts holds a timestamp counter from bootup in
> nanosecs. It currently uses the sched_clock to record, but may change
> later to something a bit better.

given that some of these clocks stop during idle... I really do care
about which timestamp is used, tracing idle with a clock that stops
during idle won't work too well.


-- 
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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