hi res timer

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Hi,

In linux 2.6 kernel the clock_getRes says that it is 1ms accuracy. 20%

I basically want to have a method run every 1 ms.  However when I run it =
on linux 2.6 kernel fedora core 2  i don't get that and I get a lot of =
jitter.

We have tried running it as root and used top to renice it to a high =
level.

What are we doing wrong? 20%
Can someone point me to an example chuck of code that shows a hi-res =
timer at over 100 hz.

thanks in advance

Re: hi res timer
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Linux is not a hard realtime system, so you will find a jitter of _any_
size if you wait long enough and produce enough stress in the system.

If you want reliable timing you need to add something like RTAI.

-Michael

Re: hi res timer
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Which 2.6 kernel, there are several of them :) Is it saying "accuracy"
or is it saying "precision?"

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What do you get and what is your definition of "a lot" of jitter?
What would be acceptable jitter for your situation?

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I seem to recall that there can be three values for HZ now in a
2.6.mumble kernel (maybe that cam in .14?)  100, 250 and 1000 I wonder
if running HZ at 1000 and perhaps playing with timeslices and such
might get things going "well enough" without having to go all the way
to what I think is RTAI?

rick jones
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Re: hi res timer
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I was playing with .14 recently and saw it there.  I'm not sure if it
came any earlier, though.
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Re: hi res timer
 > I wonder
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If you don't mind that _sometimes_ the timing condition is not met, you
are fine (2.6 is said to be a better _soft_realtime_ system than
previous versions). But there is no guarantee.

-Michael

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