linux-kernel - Re: [BISECTED] 2.6.35.*: horrible (exponential? >linear) slowdown to unusability (HPET)

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Message-ID: <AANLkTi=R5Qkdgvt=Gb_EGg-i59z07WvfGY3fsM+unsBN@mail.gmail.com>
Date:	Thu, 9 Sep 2010 20:14:31 -0400
From:	John Drescher <drescherjm@...il.com>
To:	Nix <nix@...eri.org.uk>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Venkatesh Pallipadi <venki@...gle.com>,
	Damien Wyart <damien.wyart@...e.fr>,
	linux-kernel@...r.kernel.org
Subject: Re: [BISECTED] 2.6.35.*: horrible (exponential? >linear) slowdown to
 unusability (HPET)

On Thu, Sep 9, 2010 at 8:08 PM, John Drescher <drescherjm@...il.com> wrote:
> On Thu, Sep 9, 2010 at 7:57 PM, Nix <nix@...eri.org.uk> wrote:
>> On 10 Sep 2010, John Drescher spake thusly:
>>
>>>> John, Damien, you seem to be experiencing this: are you using HPET as
>>>> your clocksource? Do you also have ICH10 82801JIs, or is this more
>>>> widespread?
>>>>
>>> I am not using hpet as my clocksource.
>>>
>>> jmd1 ~ # uname -a
>>> Linux jmd1 2.6.35-std160-amd64 #2 SMP Fri Aug 13 18:42:02 UTC 2010
>>> x86_64 Intel(R) Core(TM) i7 CPU 920 @ 2.67GHz GenuineIntel GNU/Linux
>>> jmd1 ~ # cat /sys/devices/system/clocksource/clocksource0/current_clocksource
>>> tsc
>>
>> Hm, interesting. Perhaps the HPET is needed anyway? (That would explain
>> why my other system, with identical specs to those above and using tsc
>> as clocksource, was seeing intermittent problems in this area.)
>>
>> But 82801JI looks like a common factor.
>
> Now the interesting part. I switched to acpi_pm 10 to 15 minutes ago
> using the following command
>
> jmd1 ~ # echo acpi_pm
>>/sys/devices/system/clocksource/clocksource0/current_clocksource
>
> and it was still slow. But now its running fast (well at lest as far
> as I can tell via a ssh connection).
>

I just booted with clocksource=acpi_pm
and its fast at boot. I have never seen that on any 2.6.35 kernel (or
3.6.36 rc). Thanks I will do some testing..

John
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