linux-kernel - Re: Unified tracing buffer

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Date:	Tue, 23 Sep 2008 19:30:38 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Masami Hiramatsu <mhiramat@...hat.com>
cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Mathieu Desnoyers <compudj@...stal.dyndns.org>,
	Martin Bligh <mbligh@...gle.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>, darren@...art.com,
	"Frank Ch. Eigler" <fche@...hat.com>,
	systemtap-ml <systemtap@...rces.redhat.com>
Subject: Re: Unified tracing buffer

On Tue, 23 Sep 2008, Masami Hiramatsu wrote:
> > So if you can test this, try it with 
> >  (a) cpufreq at a fixed _low_ value (to not cause overheating)
> >  (b) with the spray-can cooling the thing and cpufreq at a fixed high 
> >      value
> > and see if the TSC is constant then.
> 
> Hi Linus,
> 
> Thank you for your advice. I tested it again according your advice,
> I did:
> - service cpuspeed stop
> - echo 1000000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed
>   and checked /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq is
>   1000000.
> - echo 1 >  /proc/acpi/thermal_zone/THM/polling_frequency
> - cooling with spray-can :)
> - cat /proc/acpi/thermal_zone/THM/temperature
>   temperature:             39 C
> 
> and ran the test.
> ---
> p0: c:1107576,	 ns:990280	 ratio:111
> p0: c:1805640,	 ns:1008787	 ratio:178
> p0: c:1998324,	 ns:1000127	 ratio:199
> p0: c:946380,	 ns:990280	 ratio:95
> p0: c:871728,	 ns:1000267	 ratio:87
> p0: c:1807380,	 ns:1007949	 ratio:179
> p0: c:1784808,	 ns:1000127	 ratio:178
> p0: c:1768488,	 ns:991676	 ratio:178
> p0: c:1802292,	 ns:1008299	 ratio:178
> p0: c:1787088,	 ns:1000406	 ratio:178
> p0: c:1999176,	 ns:1000896	 ratio:199
> p0: c:881364,	 ns:991956	 ratio:88
> p0: c:1802712,	 ns:1008019	 ratio:178
> p0: c:1787088,	 ns:998590	 ratio:178
> ---
> this seems not so stable yet. :-(
> 
> After test I checked temperature again.
> # cat /proc/acpi/thermal_zone/THM/temperature
> temperature:             39 C
> 
> Hmm, 39 C is not so high. I wouldn't be surprised even if this
> is an individual product bug. Anyway, currently, Linux itself
> works well on this laptop with hpet.:-)

Do you have C-States enabled on that machine ?

ls /sys/devices/system/cpu/cpu0/cpuidle/

has it more than a state0 entry ?

If yes, please do:

cat /sys/devices/system/cpu/cpu0/cpuidle/stateX/usage

where X is the highest number in there.

cat /proc/acpi/processor/CPU0/power

might be useful as well.

Thanks,

	tglx
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