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Message-ID: <4C8FF5DB.8000207@gmail.com>
Date: Wed, 15 Sep 2010 00:23:23 +0200
From: Artur Skawina <art.08.09@gmail.com>
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To: Nix <nix@esperi.org.uk>
CC: Thomas Gleixner <tglx@linutronix.de>,
        Venkatesh Pallipadi <venki@google.com>,
        Damien Wyart <damien.wyart@free.fr>,
        John Drescher <drescherjm@gmail.com>,
        Suresh Siddha <suresh.b.siddha@intel.com>,
        LKML <linux-kernel@vger.kernel.org>, "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [BISECTED] 2.6.35.*: horrible (exponential? >linear) slowdown
 to unusability (HPET)
References: <87eid282pj.fsf@spindle.srvr.nix>	<alpine.LFD.2.00.1009101022400.2477@localhost6.localdomain6>	<alpine.LFD.2.00.1009141207310.2416@localhost6.localdomain6> <878w34qdu0.fsf@spindle.srvr.nix>
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> On 14 Sep 2010, Thomas Gleixner said:
>> Another question. If you add hpet=verbose (or revert that commit) does
>> the printk_once in hpet_set_next_event() show up in dmesg ?
>>
>>     "hpet: compare register read back failed."

Since adding back that extra read, the box here, which previously
was showing the symptoms every couple of days, has been ok; so i'm
now ~80% sure this change was indeed the cause. Nothing new in logs. 

$ dmesg | grep -i hpet 
ACPI: HPET 00000000bfee5dc0 00038 (v01 GBT    GBTUACPI 42302E31 GBTU 00000098)
ACPI: HPET id: 0x8086a201 base: 0xfed00000
hpet clockevent registered
HPET: 4 timers in total, 0 timers will be used for per-cpu timer
hpet0: at MMIO 0xfed00000, IRQs 2, 8, 0, 0
hpet0: 4 comparators, 64-bit 14.318180 MHz counter
rtc0: alarms up to one month, 242 bytes nvram, hpet irqs
$

artur