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Re: [Xen-devel] How to increase timer resolution?

To: Robert Kaiser <kaiser@xxxxxxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] How to increase timer resolution?
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Sun, 14 Sep 2008 19:11:45 +0100
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On 14/9/08 18:53, "Robert Kaiser" <kaiser@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

> On Sunday 14 September 2008 18:41:05 Keir Fraser wrote:
>> The set_timer() infrastructure is not actually tick-based. With an APIC
>> you'll get timer accuracy of around 100us (this figure because we service
>> timer handlers up to 100us before the deadline specified to set_timer(),
>> just to avoid multiple timer interrupts for close-together events). Without
>> this extra fudge factor you'd get accuracy down to microsecond resolution.
> Aha, the TIME_SLOP constant, right? So is it safe to simply reduce this
> to -say- 10us in  order to get a 20us resolution? Will check his out as soon
> as I have a suitable test machine.

Yes, frankly you can set it to zero for your purposes.

 -- Keir

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