Subject: Tracing power_end on kernel 2.6.32.8
From: Robert =?ISO-8859-1?Q?Sch=F6ne?= <robert.schoene@tu-dresden.de>
To: Arjan van de Ven <arjan@linux.intel.com>
Cc: Ingo Molnar <mingo@elte.hu>, Li Zefan <lizf@cn.fujitsu.com>,
       linux-kernel@vger.kernel.org
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Date: Mon, 15 Feb 2010 11:44:15 +0100
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Hi,
I have a question regarding the event "power/power_end".
For the standard linux kernel (2.6.32.8), it's just not reported -
neither for the /sys/kernel/debug/tracing nor for the sys_perf_open
approach.

System:
	Intel Core 2 Quad,
	Kernel 2.6.32.8,
	for sys_perf_open:always using sampling counters,
	(Kernel 2.6.33-rcX should show the same behavior)

After finding "my" c-state procedure in arch/x86/kernel/process.c
(which was "static void mwait_idle(void)" btw), I added a
trace_power_end call on the correct line:
...
		else
			local_irq_enable();
	} else
...
->
...
		else
			local_irq_enable();
		trace_power_end(0);
	} else
...
Now the event was reported on /sys/kernel/debug/tracing, but still not
for sys_perf_open.

Then I had the idea, that trace_power_end's argument should be the same
as the 2nd argument of the previous power_start.

That worked.

However, things to be done are: add trace_power_end's to some
process.c's procedures.


Bye Robert

-- 
Robert Schoene
Technische Universitaet Dresden
Zentrum fuer Informationsdienste und Hochleistungsrechnen
01062 Dresden

Tel.: (0351) 463-42483, Fax: (0351) 463-37773
E-Mail: Robert.Schoene@tu-dresden.de

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