[mythtv-users] Fixed!: Nvidia Sync to Vblank pegging cpu in X

foo bar foobum at gmail.com
Tue Dec 19 16:11:56 UTC 2006

On 12/17/06, J. Miller <mythtv.org at elvenhome.net> wrote:
> I've been fighting the scourge of myth causing X to consume 100% of the
> CPU when Xv Sync to Vblank is turned on in nvidia-settings.  Everything
> works just fine with it unchecked but that is the only sync setting that
> gives me a perfect picture with no tearing.  Myth's native OpenGL sync
> still tears a little.  The problem turned out to be the modeline I was
> using.  It was a 1368x768 56Hz modeline which apparently triggered the
> issue.  I switched to a 1360x768 60Hz modeline and now everything works
> peachy.  X still starts consuming large amounts of CPU occasionally but
> it quickly drops back down to the 2-4% range.  I'm not 100% sure that it
> was the refresh but a modeline change did the trick.  Hopefully posting
> this here will help point others that have the same problem in a new
> direction.
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NVIDIA have added an option in (I think) 9626 to poll() instead of busy-wait
for vblank, which fixes the high cpu usage when sync to vblank is switched
on. It's called "UseEvents".
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