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Old 04-01-06, 09:02 AM   #49
Linuxhippy
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Default Re: Slow AA text rendering in KDE

I wrote a small QT application which does not more than painting strings to screen, its my first QT app so don't expect too much.

It prooves my estimates that the GF6600 system is about 4x slower than my old GF488Go powerd laptop.
Therefor this is NOT an KDE problem, nor related to badly written applications!

This benchmark uses the default font which is on all of my three systems Sans with size 10. If you plan to run it yourself make sure the window is completly ereased (minimize and show it to get this result). not-complete repaints will show with shorter times.

You can find it here:
www.kewlstuff.de/qtperf (precompiled for fedora core4)
www.kewlstuff.de/qtperf.cpp

Here are the results of my system:
AMD Duron 800 / VIA KT133 / FX5200 / FC4 from-cd:
RGB Subpixel AA: 53s
Greyscale Subpixel AA: 4s
No AA: 3s

Pentium4 Northwood 2.6ghz / SiS chipset / GF488Go / FC4 updated to latest
RGB Subpixel AA: 32s
Greyscale Subpixel AA: 2s
No AA: 1s

AMD Sempron 3100+ / nForce4 / GF6600 PCIe / FC4 from-cd
RGB Subpixel AA: 116s
Greyscale Subpixel AA: 1s
No AA: 1s

lg Clemens

PS: Note that KDE seems to leave subpixel-AA enabled if you had it enabled but just disable the subpixel-checkbox in the subpixel-dialog (bug?).
Thats why I first believed that non-subpixel-AA is slow too. If you select subpixel-greyscale instead kde disables rgb-subpixel and its as fast as non-subpixel-AA.
Edit: This only affects KDE-3.4, KDE-3.5 sets subpixel-aa right if you disable the checkbox.

Last edited by Linuxhippy; 04-01-06 at 01:37 PM.
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Old 04-01-06, 04:40 PM   #50
piotrq__
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Question Re: Slow AA text rendering in KDE

Hello!

My config is: Duron 1800 MHz, GeForce 3 Ti, running SUSE 10 with KDE 3.5.1 QT 3.4, X.Org 6.9 $ nVIDIA 8178 RenderAccel true + Composite extension enabled.
Here are my results after running qtperf:

Subpixel ON:
./qtperf
QPainter::setPen: Will be reset by begin()
Painting 100000 strings took: 40

Subpixel OFF:
./qtperf
QPainter::setPen: Will be reset by begin()
Painting 100000 strings took: 3

Antialiasing completely OFF:

./qtperf
QPainter::setPen: Will be reset by begin()
Painting 100000 strings took: 2


Rendering is 10x slower with subpixel enabled... Well... I don't think the difference should be this big, should it ?
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Old 04-02-06, 03:53 AM   #51
xorbe
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Default Re: Slow AA text rendering in KDE

Cool, I'll try this on the G200 and nV cards -- but I'm out of town and will try later.
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Old 04-02-06, 04:49 AM   #52
Linuxhippy
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Default Re: Slow AA text rendering in KDE

Quote:
Originally Posted by piotrq__
Hello!
Rendering is 10x slower with subpixel enabled... Well... I don't think the difference should be this big, should it ?
Well this seems a bit slow for your configuration (compared to my Duron800, but maybe the FX5200 supports faster readback), however the 10x difference is completly normal.
I guess you don't experience those problems 6600 users talk about :-)

lg Clemens
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Old 04-02-06, 08:38 AM   #53
Ewald
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Default Re: Slow AA text rendering in KDE

On this AMD X2 3800 with nVidia 6600 card (400 MHz GPU clock), running
Mandriva 2006 I get

No AA:
Painting 10000 strings took: 126 ms

AA without subpixel:
Painting 10000 strings took: 8481 ms
This is strange as other people say it should be fast.

AA with RGB subpixel:
Painting 10000 strings took: 8402 ms

AA with grayscale subpixel:
Painting 10000 strings took: 6041 ms

So antialiasing makes things go ~60x slower.

btw I modified the time reading code a bit:
float udiff = tv2.tv_usec - tv1.tv_usec + 1e6*( tv2.tv_sec - tv1.tv_sec );
printf("Painting %d strings took: %.0f ms\n", i, 1e-3*udiff );
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Old 04-02-06, 09:02 PM   #54
xorbe
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Default Re: Slow AA text rendering in KDE

Stock 6800GT on a 10x250 A64, Mandriva Cooker x86_64.
g++ -O2 -march=k8 -I /usr/lib/qt3/include -L/usr/lib/qt3/lib64 -lqt-mt qtperf.cpp

Driver nvidia 8178 patched for 64-bit 2.6.16-15mdk:
(RenderAccel only helps the AA grey case.)
No-AA:
Painting 10000 strings took: 52 ms
AA grey medium:
Painting 10000 strings took: 12484 ms
Painting 10000 strings took: 93 ms (option "RenderAccel" "1")
AA sub-hinting medium:
Painting 10000 strings took: 12564 ms

Driver nv:
No-AA:
Painting 10000 strings took: 73 ms
AA grey medium:
Painting 10000 strings took: 9093 ms
AA sub-hinting medium:
Painting 10000 strings took: 9196 ms

Driver vesa:
No-AA:
Painting 10000 strings took: 293 ms
AA grey medium:
Painting 10000 strings took: 329 ms
AA sub-hinting medium:
Painting 10000 strings took: 305 ms

Driver nvidia on Ti 4200:
No-AA:
Painting 10000 strings took: 50 ms
AA grey medium:
Painting 10000 strings took: 8136 ms
AA sub-hinting medium:
Painting 10000 strings took: 8179 ms

Driver nvidia on FX 5900XT:
No-AA:
Painting 10000 strings took: 51 ms
AA grey medium:
Painting 10000 strings took: 8027 ms
AA sub-hinting medium:
Painting 10000 strings took: 8070 ms

Driver radeon on ATi Radeon 9600:
No-AA:
Painting 10000 strings took: 75 ms
AA, grey:
Painting 10000 strings took: 306 ms
AA, sub-hinting:
Painting 10000 strings took: 7374 ms

Driver via on 1GHz VIA Nehemiah w/integrated Castlerock (Mandriva cooker, 2.6.16-15mdk again)
No-AA:
Painting 10000 strings took: 1482 ms
AA grey medium:
Painting 10000 strings took: 2512 ms
AA sub-hinting medium:
Painting 10000 strings took: 1980 ms

Driver vesa on 1GHz VIA Nehemiah w/integrated Castlerock:
No-AA:
Painting 10000 strings took: 1714 ms
AA grey medium:
Painting 10000 strings took: 2220 ms
AA sub-hinting medium:
Painting 10000 strings took: 1756 ms

Clearly all the back-ends except "vesa" have problems. VIA seems to be consistent too (yes, it's a *slow* machine). I visually verified that vesa was actually doing AA.

Also, put a printf in the main loop, and note that qtperf hangs every ~2000 paints in nvidia's slow cases.

I have the kwrite versus kedit speed issue answer. I looked at the source code for KDE 3.5.2 -- kedit draws the screen line by line -- that's "fast enough" even with poor AA performance. But kwrite/kate appear to draw character by character -- and that trips over the nVidia performance issue. (A KDE dev claims this is fixed for 4.0 version.) For the curious, search for drawText within:
konstruct/kde/kdelibs/work/kdelibs-3.5.2/kate/part/katerenderer.cpp
konstruct/kde/kdeutils/work/kdeutils-3.5.2/kedit/kedit.cpp

btw, gtk is WORSE than qt! Here's the 6800GT on gtk+2.0-2.8.16:

No-AA:
Painting 10000 strings took: 7126 ms
AA grey medium:
Painting 10000 strings took: 12511 ms
AA sub-hinting medium:
Painting 10000 strings took: 11129 ms

Last edited by xorbe; 04-03-06 at 03:09 AM.
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Old 04-03-06, 04:57 AM   #55
Linuxhippy
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Default Re: Slow AA text rendering in KDE

Quote:
Clearly all the back-ends except "vesa" have problems.
Well the reason why vesa and via don't have this problems is because i guess the via card is shared memory and vesa is it too (or at least rendering happens in system-ram).
Therefor this drivers don't need the additional readback from VMRAM which is what hurts so much compared to the other results. Furthermore vesa does not have any accalerated routines thats why its consistent - blending is always done by CPU.

Quote:
btw, gtk is WORSE than qt! Here's the 6800GT on gtk+2.0-2.8.16:
I guess this is because you don't get that bad numbers I get (haven't seen any results compareable to mine). Your subpixel slowdown factor is quite similar to what I get on my fast machines.

I wonder wether anybody can explain why my fastest machine performs only have as fast as my slowest.

In fact my Duron800/FX5200 is able to render subpixel-AA strings twice as fast as my 1.8ghz Sempron (4 times more L2 cache, faster architecture) with a GF6600/256mb ram.
Its the same software (same xorg version, same nvidia driver, same kernel).
It was not my intetion to buy a new one and get something that performs like crap!

lg Clemens
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Old 04-03-06, 06:03 AM   #56
d13f00l
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Default Re: Slow AA text rendering in KDE

Font AA/subpixel hinting on:
Painting 100000 strings took: 115

Oh my. Almost a couple minutes. X is sitting at 99% CPU usage.

g++ qtperf.cpp -I /usr/qt/3/include -L/usr/qt/3/lib -lqt -O3 -o qtperf

Haha.
Using a bitmap font(no AA/subpixel hinting)
Painting 100000 strings took: 1
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Old 04-03-06, 06:45 AM   #57
Linuxhippy
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Smile Re: Slow AA text rendering in KDE

well than we both have almost the same results. *horray*
you: 115s
me: 116s

at least one who can reproduce my problems

lg Clemens
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Old 04-03-06, 10:59 AM   #58
xorbe
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Default Re: Slow AA text rendering in KDE

Linuxhippy, I am rendering only 10000 times. 100k times is 125s! We got tired of waiting so long...
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Old 04-03-06, 11:41 AM   #59
Linuxhippy
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Default Re: Slow AA text rendering in KDE

Quote:
Originally Posted by xorbe
Linuxhippy, I am rendering only 10000 times. 100k times is 125s! We got tired of waiting so long...
Sorry, I just overlooked that. Thought that 12s aren't that bad

lg Clemens
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Old 04-03-06, 12:21 PM   #60
xorbe
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Default Re: Slow AA text rendering in KDE

So the next question is, how can we force software rendering of all fonts on Linux? Or get the nVidia driver fixed?
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