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[SOLVED] Weird refresh rate lock (?) on Intel 915
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Subi
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Joined: 09 Dec 2008
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PostPosted: Thu Nov 19, 2009 11:22 pm    Post subject: [SOLVED] Weird refresh rate lock (?) on Intel 915 Reply with quote

Yesterday I did emerge world on an intel-powered board I have in an arcade cab in my front room. This bumped me up to xf86-video-intel.2.8.1 amongst other things.

The most noticable effect is that OpenGL apps larger than about 800x600 seem locked to the refresh rate of my monitor. For instance, glxgears will happily run at 250 fps in 256x256, but as soon as its stretch to, say 800x600, it plummets to 75. This used to still be around the 200 mark.

The other weird thing is that if an app dips under 75, it instantly goes to 37. Then below that it goes to 25. Nothing inbetween. I find this highly suspicious, simply because 75 / 2 == 37.5 and 75 / 3 == 25. It's like the apps are all locked to the monitor refresh rate in some weird manner.

I tried disabling the vblank, both on the command line and using driconf, but to no effect (enabling it also makes no difference). These apps used to run a whole lot quicker (glxgears would do about 300-250). I know the new drivers have been rewritten quite a bit, but I'd hope it'd make things better, not worse.

(Also, I constantly get an error "module i915 not found" despite the fact that it's compiled into the kernel, and CTRL-ALT-BACKSPACE doesn't work anymore. And OpenAL is now completely silent whatever alsamixer is set to. But these are other problems ;) )

I can't get to the xorg.conf at the moment, but it's nothing special. Thanks for any help!


Last edited by Subi on Tue Dec 01, 2009 6:09 pm; edited 1 time in total
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baeksu
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Joined: 26 Sep 2004
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PostPosted: Fri Nov 20, 2009 12:18 am    Post subject: Reply with quote

glxgears is not a good benchmarking tool. If you don't have any other graphical problems (low framerates on games, stuttering window transitions), I would just ignore the results glxgears gives. If the gears turn smooth, it's working fine, isn't it?

"Module not found" is not that surprising considering the module doesn't exist, right?

Ctrl+alt+backspace doesn't work because the default in X was changed to disabled. To re-enable it, add:
Code:
Section "ServerFlags"
Option "DontZap" "false"
EndSection
or something similar to your xorg.conf (depends on what you have in the file already).
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Subi
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PostPosted: Fri Nov 20, 2009 9:25 am    Post subject: Reply with quote

DontZap doesn't seem to re-enable Ctrl-Alt-Backspace, even with HandleSpecialKeys. It still just gives me umlaut-y :(

I know glxgears isn't ideal (no textures, for a start) but it isn't just that - everything (my own apps, other peoples, etc) has slowed down to some factor of the monitor refresh rate if it uses OpenGL. Yes, they're all working fine, but they're slower, which affects gameplay. If they'd be steady, there wouldn't be a problem, but they tend to flicker between 75 and 37, which gives a very stuttering performance in things like vertical shooters.
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PostPosted: Fri Nov 20, 2009 4:33 pm    Post subject: Reply with quote

hi there

I'm on i915, and will say the absolute most detrimental thing I've done to cause such a lockup is enabled KMS (kernel mode setting) in the kernel

trying to run glxgears with KMS ticked on, I'd get around 35FPS, shortly after having X lock up completely and have to hard boot the thing

Without KMS my performance is brilliant

Can you post the following?

zcat /proc/config.gz |grep DRM wrote:

Code:

CONFIG_DRM=y
# CONFIG_DRM_TDFX is not set
# CONFIG_DRM_R128 is not set
# CONFIG_DRM_RADEON is not set
# CONFIG_DRM_I810 is not set
# CONFIG_DRM_I830 is not set
CONFIG_DRM_I915=y
# CONFIG_DRM_I915_KMS is not set
# CONFIG_DRM_MGA is not set
# CONFIG_DRM_SIS is not set
# CONFIG_DRM_VIA is not set
# CONFIG_DRM_SAVAGE is not set


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Subi
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PostPosted: Mon Nov 23, 2009 5:31 pm    Post subject: Reply with quote

I had no /proc/config.gz, but in /usr/src/.config there is the following:

Code:

CONFIG_DRM=y
# CONFIG_DRM_TDFX is not set
# CONFIG_DRM_R128 is not set
# CONFIG_DRM_RADEON is not set
# CONFIG_DRM_I810 is not set
# CONFIG_DRM_I830 is not set
CONFIG_DRM_I915=y
# CONFIG_DRM_I915_KMS is not set
# CONFIG_DRM_MGA is not set
# CONFIG_DRM_SIS is not set
# CONFIG_DRM_VIA is not set
# CONFIG_DRM_SAVAGE is not set


I've also not got KMS enabled (enabling it has no apparant effect on X, but causes my console to only use the top left hand quarter of the screen ;) )
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Subi
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PostPosted: Tue Dec 01, 2009 6:08 pm    Post subject: Reply with quote

Found it. For those having a similar issue, you need to disable option "SwapbuffersWait" in xorg.conf.

driconf, vblank, GLX_SGI_swap_control, and now this. So many ways to kill your framerate. ;)
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