Re: tvtime and the Linux 2.6 scheduler

[Billy Biggs <vektor@dumbterm.net>]

  Hi Con, thanks for your reply.

Con Kolivas (kernel@kolivas.org):

> 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.

  We call XvShmPutImage and then do an XSync, which will wait until X
sends a message indicating it has processed all outstanding requests.
The XvShmPutImage uploads the image to video memory immediately, so the
call to XSync blocks us until it is complete.  We are not preempting the
X server.

  I will get accurate information about the priorities of all processes
involved here.

  -Billy