Messages in this thread | | | Date | Fri, 8 Aug 2003 14:09:50 -0700 | Subject | Re: Ingo Molnar and Con Kolivas 2.6 scheduler patches | From | Bill Huey (Hui) <> |
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On Wed, Jul 30, 2003 at 09:46:41AM -0500, Daniel Phillips wrote: > On Tuesday 29 July 2003 08:56, Timothy Miller wrote: > > ...since we're dealing with real-time and audio issues, is there any > > way we can do this: When the interrupt arrives from the sound card so > > that the driver needs to set up DMA for the next block or whatever it > > does, move any processes which talk to an audio device to the head of > > the process queue? > > That would be a good thing. To clarify, there are typically two buffers > involved: > > - A short DMA buffer > - A longer buffer into which the audio process generates samples > > There are several cycles through the short buffer for each cycle through the > long buffer. On one of these cycles, the contents of the long buffer will > drop below some threshold and the refill process should be scheduled, > according to your suggestion. Developing a sane API for that seems a little > challenging. Somebody should just hack this and demonstrate the benefit. > > In the meantime, the SCHED_SOFTRR proposal provides a way of closely > approximating the above behaviour without being intrusive or > application-specific.
You might also like to think about driving the scheduler with an interrupt from the DMA device, if it's regular, or VBL (vertical retrace) for video/graphics applications. IRIX's REACT/pro RT system does stuff like this.
http://techpubs.sgi.com/library/tpl/cgi-bin/getdoc.cgi?coll=0650&db=bks&srch=&fname=/SGI_Developer/REACT_PG/sgi_html/pr02.html
It's in their frame scheduler section.
bill
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