Messages in this thread | | | From | Con Kolivas <> | Subject | Re: tvtime and the Linux 2.6 scheduler | Date | Mon, 24 May 2004 02:54:19 +1000 |
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Hi
On Mon, 24 May 2004 01:48 am, Billy Biggs wrote: > I am the author of tvtime, a TV application with advanced image > processing algorithms. Some users are complaining about poor > performance under Linux 2.6, and I would like more information about how > tvtime will be treated by the scheduler. Here is an example of the > intended usage: > > - Program running as root and SCHED_FIFO
snip
> 33 ms : time per NTSC frame
snip
The followup email from someone describing good performance may help us understand what's going on. Your example of poor performance is one when the cpu performance is marginal to get exactly 30 fps processed and on the screen. The cpu overhead in 2.6 is slightly higher than 2.4 so a borderline case may be just pushed over.
A program running as sched_fifo it will preempt absolutely everything regardless of how it behaves. It sounds like it's giving X less cpu time to draw the frame each time until eventually the processing fails to capture the frame and then X smooths out again. I cant pretend to understand how your application blocks (as you say) between X and tvtime, but does tvtime not try to schedule until X has finished using up cpu or will it just run off the timer and preempt X away? You say changing priorities doesnt help, but I cant tell if you tried this: run the processing sched_normal at lower priority than X.
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