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Old 03-06-06, 09:35 AM   #1
Linuxhippy
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Default Slow AA text rendering in KDE

Hi there,

I've just bought a new pc with Sempron3100+/nForce4/GF6600 and I experience very slow text rendering performance under KDE when AA is enabled (no difference wether subpixel-aa or normal grayscale AA is used). I've renderaccel enabled.
It is much slower than on my GF488Go powered laptop which has a card which is based on gf4mx technology :-/

Thank you in advance, lg Clemens
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Old 03-06-06, 12:08 PM   #2
Linuxhippy
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Default Re: Slow AA text rendering in KDE

Btw. I know that other guys too have this problem, I read about it at least once here and on www.heise.de another user mentioned this problem.

Another configuration which works ok for me: Duron800 with GF5200

I simply can't see any reason except a bug why a Duron800/GF5200 should outperform an Sempron-1.8ghz/GF6600 by at least a factor of 5-10x.

lg Clemens
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Old 03-06-06, 12:21 PM   #3
pe1chl
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Default Re: Slow AA text rendering in KDE

What is your definition of "slow"? Is this something I should notice right away, or is it something like "my glxgears gives only 6000fps and it should be 9000"?
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Old 03-06-06, 12:53 PM   #4
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Default Re: Slow AA text rendering in KDE

Quote:
Originally Posted by pe1chl
What is your definition of "slow"? Is this something I should notice right away, or is it something like "my glxgears gives only 6000fps and it should be 9000"?
By slow we mean damn slow - you can see the text being rendered.

AA fonts just seem not to be accelerated....
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Old 03-06-06, 01:00 PM   #5
pe1chl
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Default Re: Slow AA text rendering in KDE

Could it be that one of the "sync to VBLANK" options is enabled?
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Old 03-06-06, 03:55 PM   #6
Linuxhippy
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Default Re: Slow AA text rendering in KDE

Quote:
Originally Posted by pe1chl
Could it be that one of the "sync to VBLANK" options is enabled?
I doubt that the X11 driver respects the "sync to VBLANK" options or at least I don't think X supports synced rendering.

With slow I mean I can't scroll fluently through kwrite, the Xorg process takes up to 99% CPU. Yes its very noticeable - with my FX5200 scrolling is absolutly no problem, but on my 6600 it maybe renders 2-3fps, just for scrolling AAed text.
Slow means REALLY nerving for serious work and since I am a programmer and sometimes use KDevelop - now I took my FX5200 and use that one now. I am disappointed.

Quote:
By slow we mean damn slow - you can see the text being rendered.
AA fonts just seem not to be accelerated....
Definitivly, I firt thought that I had renderaccel diabled but enabling it brought exactly null speed increase. No difference wether grayscale AA or subpixel rendering is used.

lg Clemens

PS: Maybe anybody experiencing thsi problem should send Nvdia the bug-report file together with a link to this discussion?
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Old 03-08-06, 03:37 PM   #7
_john_i_
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Default Re: Slow AA text rendering in KDE

I experience this problem too, and it is an issue when using color subpixel rendering of fonts. If you disable the subpixel rendering it will be fast again, although not quite as nice looking.
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Old 03-08-06, 04:10 PM   #8
Lethe
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Default Re: Slow AA text rendering in KDE

What versions of KDE would be nice to know.

Nick
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Old 03-09-06, 11:04 AM   #9
_john_i_
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Default Re: Slow AA text rendering in KDE

Any 3.3, 3.4, or 3.5 KDE versions suffer from this as does any QT application using subpixel rendering. I have not used any older KDE versions since noticing this. Also it seems only the FX6600 series is affected as far as I've been able to determine. Anyone with a non 6600 have this problem? My old geforce3, geforce4, and fx5200 work fine.

Subpixel rendering works better in non-QT application like firefox, and other GTK apps.
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Old 03-11-06, 06:48 AM   #10
Linuxhippy
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Default Re: Slow AA text rendering in KDE

Again, I think it would be best if anybody experiencing this problem would send a short description including the output of nvidia-bug-report to linux-bugs@nvidia.com

Thank you in advance, lg Clemens
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Old 03-11-06, 09:34 AM   #11
netllama
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Default Re: Slow AA text rendering in KDE

There's no need to send anything to linux-bugs@nvidia.com, as the same people who respond to linux-bugs respond here (including me).

I don't see anything in this thread to suggest that this is an nvidia driver bug. This sounds like a KDE bug, especially if its not present anywhere but in KDE/qt based applications. If I run a konsole and gnome-terminal side by side, with the same font, and dmesg in an infinite while loop, there is noticable and significant lag only in the konsole window. If there was a driver bug, I'd expect both windows to exhibit the same latency.

Has anyone submitted a bug to the KDE developers?

Thanks,
Lonni
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Old 03-11-06, 11:23 AM   #12
Linuxhippy
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Default Re: Slow AA text rendering in KDE

Sorry about that, did not know that nvidia devs are also reading this forum. Great to know!

Well but why does this only happen with 6xxx cards and not with my GF5200FX or the Gf488Go in my Laptop (same KDE version + same driver version).
All the time is spent inside of the Xorg process, if I remove my 6600 and plug my 5200 in everything works like expected.
Could it be that KDE/QT just use features which touch a corner case in the nvidia drivers?

I'll post my sysprof results later, maybe this could give some details...

lg Clemens
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