2.6.26.6-rt11 nanosleep() does have accurate behavior

2.6.26.6-rt11 nanosleep() does have accurate behavior

[Gautam Thaker]

I recently started to study how nanosleep() behaves under 2.6.26.6-rt11 compiled in in FULL PREEMPT, uniprocessor mode. 
  I find that between 2.6.20-rt8 and this new kernel something has changed and nanosleep() is back to its old behavior 
or sleeping for next higher number of msec rather than carefully following the "y=x" line.

I don't follow the RT world closely enough, but is this a regression or an expected change in behavior? The link below 
show the results very clearly.

http://www.atl.external.lmco.com/projects/QoS/documents/nanosleep_1.png

Gautam

Re: 2.6.26.6-rt11 nanosleep() does have accurate behavior

[Leon Woestenberg]

Hello Gautam,

On Fri, Nov 7, 2008 at 4:56 PM, Gautam Thaker <gautam.h.thaker@lmco.com> wrote:
> I recently started to study how nanosleep() behaves under 2.6.26.6-rt11
> compiled in in FULL PREEMPT, uniprocessor mode.  I find that between
> 2.6.20-rt8 and this new kernel something has changed and nanosleep() is back
> to its old behavior or sleeping for next higher number of msec rather than
> carefully following the "y=x" line.
>
> I don't follow the RT world closely enough, but is this a regression or an
> expected change in behavior? The link below show the results very clearly.
>
> http://www.atl.external.lmco.com/projects/QoS/documents/nanosleep_1.png
>
This suggests (to me) that you probably did not enable HRTIMERS?

Regards,
-- 
Leon