[coyotos-dev] coyotos.sleep, sleepTill, the epoch

[Valerio Bellizzomi]

On 12/02/2007, at 9.49, Jonathan S. Shapiro wrote:

>A 0.25ms tick counter will eat 4% of the CPU **if it is implemented in
>the kernel**. That goes to ~10% if it is implemented at user level.

Eww! Not only it is measurable, but it is also a lot. Too much.

>
>You don't want a tick counter because you don't actually ask for time of
>day 4,000 times per second. What you want is a free-running interval
>counter that can be queried by the ToD implementation at need.

I am interested to know the time resolution for use in sampling
applications that grab data from some external source via a PCI card. 4000
times per second is really much much more than what I expect to use.

>
>shap
>
>On Mon, 2007-02-12 at 02:54 +0100, Valerio Bellizzomi wrote:
>> On 09/02/2007, at 15.40, Jonathan S. Shapiro wrote:
>> 
>> ...
>> 
>> >Something you definitely do NOT want is a 1ms granularity interrupt to
>> >maintain a tick counter. On current hardware this will account for a
>> >measurable fraction of the machine.
>> 
>> To what granularity do I want ?
>> 
>> What fraction % ?
>> 
>> 
>> Tick tick tick,
>> val
>> 
>> 
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>-- 
>Jonathan S. Shapiro, Ph.D.
>Managing Director
>The EROS Group, LLC
>+1 443 927 1719 x5100
>
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