[Bug 26599] torcs performance regression (git 47136fa)

[Dave Witbrodt]

On 05/11/2010 06:07 AM, bugzilla-daemon at freedesktop.org wrote:
> https://bugs.freedesktop.org/show_bug.cgi?id=26599
>
> Michel Dänzer<michel at daenzer.net>  changed:
>
>             What    |Removed                     |Added
> ----------------------------------------------------------------------------
>              Summary|Radeon DDX 6.12.99 (git     |torcs performance
>                     |47136fa) performance        |regression (git 47136fa)
>                     |regression                  |
>
> --- Comment #10 from Michel Dänzer<michel at daenzer.net>  2010-05-11 03:07:59 PDT ---
> (In reply to comment #8)
>> After upgrading to Ubuntu Lucid, fullscreen video playback is slow/choppy.
>
> This report is about torcs. Please track your problem in another report or just
> discuss it on the xorg-driver-ati mailing list.
>
> P.S. Dave, can this report be resolved per comment #7?

For the record, this bug was about the "vline" feature in the radeon 
driver, and 'torcs' was merely the metric being used to identify and 
measure the impact it had on performance.

Regarding closing the bug:  I assumed that the developers would close 
the "bug" after Alex identified (in comment 2) that the problem was 
caused by vline... and it was actually a feature, not a bug.

When the bug was NOT closed by any developer, I assumed (maybe wrongly?) 
that the impact of vline (versus radeon with vline removed) was still of 
some interest to the developers.  As a result, I began reporting my 
results once or twice a month of testing my latest radeon update from 
git with and without the vline feature.


In hindsight, I think this was not a bug; it was true that when vline 
was first introduced that the track I was using in 'torcs' went from 
playable to unplayable.  Vline does cause a decrease in max frame rate, 
but something else got fixed (who knows what?  DRM?  Mesa?) which 
rendered 'torcs' playable even with vline.


I sympathize with AttilaN, though:  one of the programs I use for 
testing OpenGL performance (prboom) has suffered a horrible performance 
regression since January or February.  The problem is, I've been testing 
'prboom' using only one map which doesn't expose the regression.  I 
accidentally played another map a few days ago -- formerly perfectly 
playable -- which was now experiencing performance issues that made it 
difficult or impossible to play.

Wanting to report a bug, I tried as many combinations of older packages 
(from Debian, and locally built from git) as I could think of -- Linux 
kernels/DRM, radeon drivers, Mesa libraries, libdrm, X servers -- and 
even going back to versions from the beginning of March, I was not able 
to find a combination of old software that made the performance 
regression disappear.

At this point, I'm totally baffled:  I don't know when the problems were 
introduced, or in what software.  I also just discovered that a 
different track in 'torcs' only allows me 5 frames per second (on HD 
4850 hardware!), even with vline removed from radeon.  I'm afraid I 
can't locate the cause of these regressions, and for now have given up 
trying.  I guess all I can do is hope the developers are seeing the same 
problems, and are able to find fixes or workarounds.

None of this has much to do with vline, though.  If a developer closes 
this bug, I will understand.  If not, I will continue to report here 
what performance differences I'm seeing in the radeon driver with and 
without the vline feature.


Thanks,
Dave W.