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Old 06-11-10, 07:23 AM   #11
Linux kernel hacker
Join Date: Feb 2009
Location: Ottawa, Canada
Posts: 173
Default Re: 256.29: Jerky VDPAU HD playback in MythTV

Mmm.. I wonder if the odd glitch with this could be resulting from nvidia-settings experiencing a page-fault while holding a mutex in the userspace portion of the driver?

Or are things clever enough to mlock() all code blocks that might acquire global mutexes?

Along those lines, I may see if I can set up a tmpfs to hold nvidia-settings and everything it uses (libs), thereby locking it all into RAM. If this eliminates the glitches, then disk-based page faults become the prime suspect for glitching in normal usage.

With MythTV as active as it is w.r.t. the disks, there's a reasonably high likelihood that idle pages are being agressively evicted from the page-cache (aka. "RAM"), and that nvidia-settings is partially paged back in each time it is invoked (every three seconds or so by the vfd app).

I'll give this theory a trial on the weekend.
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