RE: [Linux-hls-devel] HLS errors appearing with cpu reservations

[Luca A. <luc...@em...>]

Hi John,
 
> It's true that without help from the scheduler, Hourglass cannot ensure
> that a thread period is synched up with its reservation.
> 
> However, this 550 ms anomaly sounds like it's too large to be explained by
> a phase difference,
Yes you are right... 550ms is too much. This seems to be some kind of
transient phenomenon happening on the startup of a periodic task (I do
not see it if the hourglass task is not periodic). I am wondering if
hourglass periodic tasks do some kind of synchronization on startup...
Ok, I'll have a look at the code.
 
> Paul, is the HLS code in the Hourglass pre-release working for you?
I just sent it to him 1 minute ago. Anyway, it is working fine for me.
If you can wait some days before the release, I have some cleanups to
do, and I have a patch for PPC support (!!!). (yes, I tested it on my
ibook ;).

> > Integrating HLS with high-resolution-timers is on my todo list, but it
> > requires some important changes to the code... It will take some time
> > (although I know how to integrate the two things, because I already did
> > something similar for another project).
> 
> Cool.  Was this the CBS scheduler you guys put into Linux?
Yes; you can compare
http://feanor.sssup.it/cgi-bin/cvsweb.cgi/cbs/src/timers.c?rev=1.8&content-type=text/x-cvsweb-markup
and
http://feanor.sssup.it/cgi-bin/cvsweb.cgi/cbs/src/hrt.c?rev=1.3&content-type=text/x-cvsweb-markup
to see the modifications that are needed.

Unfortunately, the latest version of the high-resolution-timers patch
still does not export some symbols that are needed for using hr timers
from a module, and an additional patch is needed.

				Luca
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