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-   -   Fedora 7 rendering stutter (http://www.nvnews.net/vbulletin/showthread.php?t=93770)

dudster 06-24-07 06:41 PM

Fedora 7 rendering stutter
1 Attachment(s)
Although Im not a "gamer" I do run flight simulators & I am having an issue with "stutter" during the simulation. The symptoms are frequent rendering freezes that last for a fraction of a second giving a choppy "stick-slip" impression.

Ive read many posts here that seem to describe the same thing. I am looking for advice on how it can be eliminated/minimized.

Im running an Intel core 2 duo cpu with a Nvidia Geforce 7600 GS based graphics card. I have tried a number of things in my xorg.conf including disabling the composite extension.

Frame rates are not the issue. The application (FlightGear) reports them to be >150 fps.

The attached bug report was taken during a simulation when the stutter was present.

netllama 06-24-07 07:12 PM

Re: Fedora 7 rendering stutter
I have a few questions:
1) Have you verified that you're using the latest motherboard BIOS?
2) What other processes are running simultaneously when thie stuttering is present?
3) Was the bug report that you attached generated, during or immediately after experiencing this problem?


dudster 06-24-07 10:54 PM

Re: Fedora 7 rendering stutter
If you look at the bug report, portion giving the xorg.log, you will see that composite is disabled. Disabling it is almost a requirement to get the simulation to run acceptably at all.

The bug report also gives quite a complete snapshot of what was running on the system at the time in the background, services, etc. As a user, I only had thunderbird email client open. Ive already checked that out by running only the simulation (i.e. nothing started by user).

yes, the bug report was captured during the simulation, as I indicated in my original post.

We have to remember that Fedora 7 is not yet one month old, sooooo we need to make allowances for that alone. Im not discounting that is could be some issue(s) with it.

As it stands, Fedora 7 + latest nvidia drivers are not a very good combo for running games or simulations.

dudster 06-27-07 02:55 PM

Re: Fedora 7 rendering stutter
netllama -

I am speculating but perhaps this issue relates to how the nvidia driver interacts with the Fedora 7 kernel with regard to state changes or event scheduling.

I would like your opinion on adjusting the "OpenGL yield behavior" discussed in chapter 11 of the README. Can this be done with the nvidia-settings tool?

Would there be negative consequences of setting it to "NOTHING" ? I understand that OpenGL will never yield in that case.

netllama 06-27-07 03:09 PM

Re: Fedora 7 rendering stutter
__GL_YIELD is an environment variable. It cannot be set via nvidia-settings.

You can certainly try setting it to NOTHING to see if it improves the situation.

dudster 06-27-07 03:42 PM

Re: Fedora 7 rendering stutter
final question before I go off & try this.

Should I export this variable from my user account profile or does it need to be root's account profile?

netllama 06-27-07 03:45 PM

Re: Fedora 7 rendering stutter
It needs to be set in the environment of the user who is using the X server.

dudster 06-27-07 09:59 PM

Re: Fedora 7 rendering stutter
Well so much for my bright idea. We can take that possibility off the list. Made no difference.

Also tried turning off server flag:

Option "AIGLX" "off"

No joy with that either. On with the hunt.

boyaci 06-28-07 02:38 PM

Re: Fedora 7 rendering stutter
I am having trouble with the Fedora 7 + Xorg server 1.3 + Nvidia (various drivers, including 9755 or 100.xx.xx) combination, too. Particularly with Java2D using the opengl pipeline in full screen exclusive mode. I will post a more detailed post on Java2D forum as it seems java2d is effected most from this. None of those problems existed with earlier Fedora Core releases.

stuartlevy 06-28-07 04:01 PM

Re: Fedora 7 rendering stutter
I'd be suspicious of background processes. Though I don't have Fedora 7,
I do have FC6. It runs a "haldaemon" which seems to be set to watch
various devices, like any CD/DVD drives, in case a disc might be inserted. Presumably it polls them. I'd want to try something like (as root)
/sbin/service haldaemon stop
and see whether the stuttering stops. If so, then try poking around in
haldaemon's configuration and see whether you can tell it to stop
watching the DVD drive. (Haldaemon does other things too -- I'm not
sure what all but it seems to be involved in CPU speed tuning -- so you
might not want to just leave it disabled.)


dudster 06-29-07 10:16 AM

Re: Fedora 7 rendering stutter
I am also suspicous of background processes & how they might affect video drivers interacting with the kernel.

I have been testing using a cvs version of FlightGear that had been running fine on FC6 several months ago. Now I have Fedora 7.

As a test I (..choke..) bought x-plane & all is well with regard to rendering during the simulation (so far). I conclude this may be an application issue rather than a system issue, at least for the behavior I have reported on at the beginning of this thread.

Nvidia may be off the hook on this one - for now :-)

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