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Old 06-08-06, 10:29 AM   #1
Cimi
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Default Great performance drop with subpixel text

Enabling subpixel anti aliasing with fonts, gtkperf (http://gtkperf.sourceforge.net/) gives me 30% performance drop than with simple anti aliasing (15 to 21 seconds).
GtkDrawingArea from 1seconds to 7 seconds
There's a way to improve the performance with driver?
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Last edited by Cimi; 06-08-06 at 10:46 AM.
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Old 06-09-06, 02:20 AM   #2
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Default Re: Great performance drop with subpixel text

Well subpixel-AA isn't done in hardware for now even on latest nvidia GPUs (although they are capable of doing so).
There are also quite serious problems with QT based problems since at least the 7xxx drivers for some special system/gpu combintions which nvidia isn't able to fix, the slowdown you see for GTK is quite normal.


Its very clear that this is because no one is interrested in 2d benchmarks any more, everybody just looks at the quake4 score and decides which board to grab.
Keeping in mind that 95% mostly use 2D functionality and >70% own an LCD monitor and use subpixel-AA this is just plain stupid.


However it seems nvidia does get more revenue back if they invest in getting the latest performance piece out of their opengl implementation than fine tuning their XRender implementation.

lg Clemens

Btw. XRender accaleration of the nvidia driver is a joke! Fix it!
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Old 06-09-06, 07:47 AM   #3
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Default Re: Great performance drop with subpixel text

Yeah, the performance hit is pretty hard. For me, the benchmark total time is 14 seconds with sub-pixel, and 7 seconds without it. Although, to be honest I don't visually notice any performance issues.
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Old 06-14-06, 06:32 AM   #4
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Default Re: Great performance drop with subpixel text

Hi guys!

Confirm here. I have 6600GT + Samsung SM730BF and subpixel AA just horrible slow.

gtkperf went down from 9.8 to 55.8 (slower by 469%!!!), all KDE apps have very noticeable perf. drop (try to resize sidebar in amarok or surf the web in konq - its reminds me windozeXp in safemode).

OK, I would be happy with grayAA if I haven't seen this patches: http://turnerdavid.neuf.fr/freetype/...t-patches.html It's absolutely beautiful! M$ suck with their ClearType! So I have to stay with subpixel AA despite of its slowness on nVidia drivers

So, nVidia guys, PLEASE stop improving your ALREADY PERFECT OpenGL and make us LCD users happy!
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Old 06-14-06, 02:45 PM   #5
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Default Re: Great performance drop with subpixel text

Quote:
Originally Posted by .:Ratmann:.

Confirm here. I have 6600GT + Samsung SM730BF and subpixel AA just horrible slow.
Yeah, the 6600 is the worst of the lot when it comes to subpixel. Look around and you will find a couple other long threads about this. My old geforce 3 was faster!
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Old 06-14-06, 04:59 PM   #6
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Default Re: Great performance drop with subpixel text

Quote:
Originally Posted by _john_i_
Yeah, the 6600 is the worst of the lot when it comes to subpixel. Look around and you will find a couple other long threads about this. My old geforce 3 was faster!
But why? What's the big changes in 2D functionality? I've also heard about lack of proper XV acceleration on 6600, is this true?

BTW, 6800 have this problems?
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Old 06-18-06, 06:15 AM   #7
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Default Wats appening NVIDIA?

I wonder wats appening. Many users claimed about tis issue and explained tat tis is a really nerving bug.

Te only reply we got is: "We're always looking for ways improving performance".
Tis contains exactly zero information.

lg Clemens
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Old 06-18-06, 08:01 PM   #8
_john_i_
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Default Re: Wats appening NVIDIA?

Quote:
Originally Posted by Linuxhippy
I wonder wats appening. Many users claimed about tis issue and explained tat tis is a really nerving bug.

Te only reply we got is: "We're always looking for ways improving performance".
Tis contains exactly zero information.

lg Clemens
Looks like you "h" key is dead. Bad news for a "H" ippy.
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Old 06-19-06, 12:15 AM   #9
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Default Re: Great performance drop with subpixel text

I managed to isolate the problem. It seems that Cairo, Pango, and the newer QT4 library all use functions that eventually boil down to calls to the XRenderCompositeText* series of functions. QT3 uses functions that end up at XRenderCompositeString*. These functions in libXrender seem pretty similar, so I believe this is the diverging point for the nvidia driver.

Chances are, the nvidia driver is providing acceleration for XRenderCompositeText correctly, but XRenderCompositeString incorrectly, in a more performance-damaging way, or not at all.

GNOME and KDE CVS (QT4) seem to be the better performing interfaces. I would give about 300% leniency to the subpixel performance simply because of the larger amount of data involved, and these two fall within that. The QT3 performance, on the other hand, is way out of line.

By the way, this problem is present on both my GeForce 3 and 7800GT, so it is NOT a 6*00 series problem.
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Old 06-19-06, 12:49 PM   #10
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Default Re: Great performance drop with subpixel text

Quote:
Originally Posted by bearoso
Chances are, the nvidia driver is providing acceleration for XRenderCompositeText correctly, but XRenderCompositeString incorrectly, in a more performance-damaging way, or not at all.
These functions end up making the same calls into the driver. The issue here is subpixel antialiasing vs. grayscale antialiasing. The former falls back to software rendering right now, which is what causes the slowdown.
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Old 06-19-06, 01:21 PM   #11
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Default Re: Great performance drop with subpixel text

Quote:
Originally Posted by AaronP
These functions end up making the same calls into the driver. The issue here is subpixel antialiasing vs. grayscale antialiasing. The former falls back to software rendering right now, which is what causes the slowdown.
So, are you saying the driver is refusing to do hardware rendering for subpixel, or the render extension libraries are assuming that it needs to do software rendering, and never sending it to the drivers?
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Old 06-19-06, 02:57 PM   #12
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Default Re: Great performance drop with subpixel text

Quote:
Originally Posted by AaronP
These functions end up making the same calls into the driver. The issue here is subpixel antialiasing vs. grayscale antialiasing. The former falls back to software rendering right now, which is what causes the slowdown.
But then why does a FX5200 outperform a GF6600 powered system with a much faster CPU by a factor of 2?
Have there been some regressions in chip-design which cause this slowdown?

lg Clemens
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