Slow AA text rendering in KDE

[Ewald]

It's not only KDE but also OpenOffice 2.0 Calc. Try scrolling through a spreadsheet
with Calc. With font antialiasing it's slower than even KDE, and without it's fast again.

The AA option is in
Tools -> Options -> OpenOffice.org -> View -> Screen font antialiasing

Strange thing is that OpenOffice Writer always seems to be fast.

So the problem is not confined to KDE and I don't think we should bother the KDE
guys with this bug/inefficiency in the NVidia driver.

[Linuxhippy]

Originally Posted by Ewald

It's not only KDE but also OpenOffice 2.0 Calc. Try scrolling through a spreadsheet
with Calc. With font antialiasing it's slower than even KDE, and without it's fast again.

I don't see this problem on my machine, could you watch the output of "top" while scrolling throw OpenOffice Calc, please?
OO has some problems with claculating which parts need to be redrawn, maybe you speadsheet just hits this problem? OO Writer and Calc use imho exactly the same drawing routines.

So the problem is not confined to KDE and I don't think we should bother the KDE
guys with this bug/inefficiency in the NVidia driver.

Well I also believe its a problem in the nvidia drivers, but can you PROOVE it. I can't thats why I am quite with such bold statements.
lg Clemens

[xorbe]

I have Mandrake 64-bit, KDE 3.5.1, and a 6800GT (2GB DDR500, 2.5GHz A64, blah blah blah)

With kwrite+AA, X usage just goes off the scale. If I were to guess, kwrite is redrawing way too much crap.

And when I turn off AA, instead kwrite cpu usage goes off the scale, though scrolling is much improved. This has to be a KDE/Qt problem. Most likely bad KDE programming. If I were energetic, I'd rebuild kde with konstruct and profile kwrite...

I have a 5900 and a 4200 right here. I'll give them a whirl.

edit: 4200, same issue. Not bothering to test the 5900, because...

... I get the *same* thing with the nv driver and vesa driver. Go harass KDE/Qt for a profile of kwrite. To demonstrate, open kwrite (AA off, nv or vesa driver) and hold down the "a" key for 30-40 characters, copy, and paste several times. kwrite simply comes to a halt at high kwrite cpu usage.

Now, for the driver "nvidia" + AA case, the rendering is offloaded to X for acceleration, and which really grinds the machine to a halt, which indicates X is poorly threaded probably.

Also, shrink kwrite down to minimum size, and note that the issue goes away. Obviously, ALL the text is redrawn every keystroke (or multiple times).

I've never really noticed this issue before, as I use Firefox and Emacs usually.

Don't make me bust out the Matrox G200 and test on that...

[debian_penguin]

xorbe: is kwrite the only app causing your cpu go skyrocketing, or is it a general kde problem?

'cause I had a similar problem with all kwrite-based applications (kate, kdevelop, kile...), and it turned out to be a problem completely unrelated to rendering (though it looked like it: scrolling is really slow, letters apprear much slower than they are typed...). It's a bug of some sort in the undo cache generation and management. I solved it by telling applications to keep trace of about 400 undoings rather than an unlimited number of those.

Well, I apologize if it is not your case

just my two cents,
d_p

[d13f00l]

Originally Posted by Linuxhippy

I don't see this problem on my machine, could you watch the output of "top" while scrolling throw OpenOffice Calc, please?
OO has some problems with claculating which parts need to be redrawn, maybe you speadsheet just hits this problem? OO Writer and Calc use imho exactly the same drawing routines.


Well I also believe its a problem in the nvidia drivers, but can you PROOVE it. I can't thats why I am quite with such bold statements.
lg Clemens

You're the one who told me to shut up about this bug. :P

Can someone check with drivers 1.0-6111? And then compare the speed to 6629 and 8178. 6111 should be fast, 6629 should be slow. If 6629 is faster than 8178, then Nvidia will look at this issue. 6111 was fast because it renders fonts incorrectly. I've been in contact with a few people about this bug. As it stands now, it's mostly a KDE bug, as there are issues with other drivers besides "nvidia" in kwrite and other KDE programs.

The next release of the nvidia driver should improve render acceleration and have lots of fixes for render, or so I'm told. I kind of doubt it will solve this KDE issue, but that's just me.

[d13f00l]

Originally Posted by debian_penguin

xorbe: is kwrite the only app causing your cpu go skyrocketing, or is it a general kde problem?

'cause I had a similar problem with all kwrite-based applications (kate, kdevelop, kile...), and it turned out to be a problem completely unrelated to rendering (though it looked like it: scrolling is really slow, letters apprear much slower than they are typed...). It's a bug of some sort in the undo cache generation and management. I solved it by telling applications to keep trace of about 400 undoings rather than an unlimited number of those.

Well, I apologize if it is not your case

just my two cents,
d_p

I just tried this, it didn't solve the issue here. Worth a shot, though.

[Ewald]

I don't see this problem on my machine, could you watch the output of "top" while scrolling throw OpenOffice Calc, please?

Hello Clemens,

Most CPU is spend in the X server, just like with KDE apps.
Please make sure that the spreadsheet is dense with text.

I wrote earlier that it didn't happen with OO Writer but that was
because I was working with documents with much whitespace.
With dense documents it gets slow for Writer as well. So it's
the 'total font area' that seems to determine the slowlyness.

Well I also believe its a problem in the nvidia drivers, but can you PROOVE it.

Well there is with certainty some inefficiency that is not there with
Matrox or ATI. But my point is more this:
It is very uncertain that KDE (and OO) can come up with a fix, and if they
do it will take a long time to reach most affected users.
But for NVidia, I believe it is within their power to fix this and
then get the fix to those affected quickly via a driver update.
I for one would be very gratefull if they did.

[firephoto]

I checked kwrite with non aa fonts and it doesn't do 100% cpu here, it's close but it never causes the display to stop updating or any noticeable affects to any other apps which isn't the case when X goes to 100%.

I've read from others elsewhere that 6629 was the last driver that works as expected and that other video cards on the same hardware worked fine with aa fonts. Also around the time I first got this 6800 card the aa fonts issue was only present with this card, not with the 5600 card. 3d was faster but for normal usage the 6800 was noticeably slower on the desktop.

There is room for improvement on the kde side of things but this problem is above and beyond the normal render issue that everyone sees in kde no matter what the hardware and it seems some change that affects the interaction between the nvidia drivers and the X server is the place to look.

[Linuxhippy]

Originally Posted by d13f00l

The next release of the nvidia driver should improve render acceleration and have lots of fixes for render, or so I'm told. I kind of doubt it will solve this KDE issue, but that's just me.

To be honest I still don't believe the problem lies in KDE or QT. Why does the exactly same setup work fast and without problems on 2 computers (GF488Go (Gf4mx makeof), FX5200) and only causes REAL problems on the fastest machine I own (Sempron 3100+ with GF6600).

If I resize a "konsole" window which contains tons of glyphs I can see how the glyphs are painted from top to bottom.
On my laptop with a GF488Go this takes aprox. 10ms, the _same_ operation with the same kde version (you only see some flicker), x-server etc. takes about 200ms on the GF6600. Same software, just another graphic card.

Its ugly - I bought an nForce4 board and have problems with sound (*wow* oss drivers *oooo*) and a GF6600 - blieved this would be an optimal combination. *zz*. Every onboard card performs better (unichrome *g*).
I am not a gamer, so 3d performance is not relevant for me.

lg Clemens

[joffe]

Originally Posted by Linuxhippy

I am not a gamer, so 3d performance is not relevant for me.

But within a year you will be begging to have your 2D desktop accelerated through OpenGL so that statement falls short... It will sound the other way round: I am not a gamer so 3d performance is relevant for me.

[xorbe]

I totally forgot about my all-VIA Epia box over in the corner with the same kernel (except 32-bit) and KDE as my nForce/nVidia box. I'll try that when I get back home. And the G200 in my main machine.

edit: Sorry, but kwrite sucks eggs on my VIA machine too, and it doesn't contain nVidia anything. I'm not even going to bother with the G200 in my main machine.

[Linuxhippy]

Well, since everybody seems to focus on kwrite I'll write a small application which will demonstrate the behaviour and output concrete numbers.