[mythtv-users] SVN multi-threading

[William Kenworthy]

On Sat, 2008-02-16 at 16:29 -0800, Yeechang Lee wrote:
> Tom Lichti <tom at redpepperracing.com> says:
> > I've seen that there have been some updates to trunk to allow
> > multi-threaded decoding of streams, and in the video profiles screen
> > there is a new 'max cpus' setting. However, that setting doesn't
> >...
> > 
> > I only ask because I am seeing more CPU usage on playback now than I
> > was a few weeks ago.
> 
> Sounds like what I noticed with my single-core Pentium 4 frontend. I
> thought that, since the CPU is Hyperthreaded and thus emulates two
> physical cores, bumping the Max CPUs number up to 2 would be a good
> thing. Not so; CPU usage for mythfrontend running 1080i Bob playback
> went from 50-70% to 100%+. So back to 1 I go.

I was privy to some tests on high end PC hardware doing searches on huge
indexed flat file databases - enabling HT caused a quite marked
slowdown.  The reason given was that HT uses unequal processing
pipelines - depending on what task was sent to which pipeline,
efficiency could (and did) suffer quite a lot.  This could be the same
here.

Also, it might be worth checking that the SMT (HT scheduler...) option
is enabled in the kernel as well as the normal SMT option - I dont
remember when it appeared in the kernel, but it wasnt always there?

BillK