[mythtv-users] bttv performance under 2.6

Chris Strom mythtv at eeeCooks.com
Thu Jul 8 08:58:58 EDT 2004


On Thu, Jul 08, 2004 at 08:53:22AM -0300, Jason Keirstead wrote:
> On July 8, 2004 08:05 am, Chris Strom wrote:
> > I am unable to make the switch to the 2.6 kernel due to _poor_
> > performance of the bttv encoding. 
> 
> That's strange. When I switched to 2.6 my performance jumped dramatically.

Well, at least it *should* be able to work.

> Are you sue it is not something else that has changed as a result of your 
> kernel change? Compiling in the wrong IDE driver so it has to use the generic 
> one, or maybe not having DMA turned on?

It certainly possible that I overlooked something, but DMA is enabled on
the hard drives.  I've got CONFIG_BLK_DEV_VIA82CXXX=y (just as in my 2.4
kernel), which is appropriate for my VIA Apollo KT266.  I have been
doing `make oldconfig' for all my 2.6 kernels, so I may be propagating
an error from version to version (I didn't do oldconfig for my first 2.6
kernel).

It's doesn't feel like it's IO bound.  When myth is recording only, the
CPU meter is rough.  It goes up and down, depending on how much work it
has to do to encode the MPEG4 stream.  If I try watching another
recording at the same time, the CPU goes flat.

Everything else on the system feels faster (web browsing, compiling,
mythfrontend).  It's just encoding/decoding MPEG4 that seems to be the
problem.  Perhaps my Athlon 900MHz is borderline for being able to
handle encoding/decoding and the additional overhead of the 2.6 kernel
pushing the CPU past the breaking point.

Any other hints?  Thanks,

Chris


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