linux-kernel - Re: various laptop nagles - any suggestions? (note: 2.6.19-rc2-mm1 but applies to multiple kernels)

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Date:	Sun, 22 Oct 2006 23:22:39 +0200
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Andrew Morton <akpm@...l.org>
Cc:	Ingo Molnar <mingo@...e.hu>, teunis <teunis@...tersgift.com>,
	linux-kernel@...r.kernel.org, Dmitry Torokhov <dtor@...l.ru>,
	john stultz <johnstul@...ibm.com>, Len Brown <lenb@...nel.org>
Subject: Re: various laptop nagles - any suggestions?   (note:
	2.6.19-rc2-mm1 but applies to multiple kernels)

On Sat, 2006-10-21 at 11:49 +0200, Thomas Gleixner wrote:
> [   11.515305] calibrating APIC timer ...
> [   11.618612] ..... tt1-tt2 831283
> [   11.618614] ..... mult: 35701101
> [   11.618616] ..... calibration result: 532021
> [   11.618619] ..... CPU clock speed is 1995.0325 MHz.
> [   11.618622] ..... host bus clock speed is 133.0021 MHz.
> 
> That looks reasonable. It really boils down to the lapic not working
> when going idle.

This LAPIC business is weird. I found two boxen, where the LAPIC timer
calibration is wrong by factor 1.8 and 2.3 on every third/fifth boot.
Unsurprisingly one is a VAIO with a CoreDuo inside, which claims to have
a 4.6GHz CPU and 390MHz bus speed occasionally. This problem seems to be
independent of the "lapic stops on C2" one. 

I have a patch ready, which should detect both problems, but having
acpi_processor as a module is painful, as we might enable the C2 states
way after we decided to use the LAPIC timer and switched over to
highres/dyntick mode. I need to find a way to back out from
highres/dyntick mode gracefully in that case except we can agree to make
the acpi_processor bits built-in only or at least make the Kconfig
tristate depending on experimental. Len ?

	tglx

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