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[Xen-devel] RE: [RFC] Remove the x86 Periodic 100HZ PIT Timer Interrupt

To: "Andi Kleen" <andi@xxxxxxxxxxxxxx>
Subject: [Xen-devel] RE: [RFC] Remove the x86 Periodic 100HZ PIT Timer Interrupt
From: "Yu, Ke" <ke.yu@xxxxxxxxx>
Date: Tue, 8 Apr 2008 09:42:57 +0800
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Thread-topic: [RFC] Remove the x86 Periodic 100HZ PIT Timer Interrupt
Andi Kleen wrote:
> "Yu, Ke" <ke.yu@xxxxxxxxx> writes:
>> * How to handle platform timer counter overflow
>> Since IBM cyclone timer/HPET timer/ACPI PM timer has large overflow
>> period (> 1s),
> ACPI PM timers are often only 24 bit and overflow in less the 5
> seconds. If you aim for longer sleep times using ACPI PM is not a
> good idea 
> -Andi

This proposal aims for longer processor C state residency, usually it is
in ms. Take native linux kernel as example, when tickless idle is not
enabled, the C state residency is usually less than 10ms. When tickless
idle is enabled, I can see C state residency as long as 50ms sometimes.
So 5s overflow period is long enough in terms of C state residency. 

Best Regards

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