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Old 04-07-06, 03:27 PM   #1
mrmailer
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Default even with 8756, minimal multitasking slows down glxgears performance

ok, here's glxgears on my geforce 6200. see if you can tell when i start doing something simple like moving gnome-terminal around

glxgears
5070 frames in 5.0 seconds = 1013.988 FPS
5013 frames in 5.0 seconds = 1002.463 FPS
4901 frames in 5.0 seconds = 980.162 FPS
3135 frames in 8.2 seconds = 383.096 FPS
173 frames in 5.8 seconds = 29.617 FPS


HELP
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Old 04-07-06, 03:31 PM   #2
netllama
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Default Re: even with 8756, minimal multitasking slows down glxgears performance

glxgears is not a useful benchmark for the reason you've stated already (its performance is easily impacted by alot of outside factors). This behavior is to be expected with glxgears regardless of driver version.

If you're seeing undesirable performance from real OpenGL applications, please provide details on how to reproduce the problem, along with an nvidia-bug-report.log.

Thanks,
Lonni
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Old 04-07-06, 03:54 PM   #3
energyman76b
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Default Re: even with 8756, minimal multitasking slows down glxgears performance

Hi,

three points:

gnome-terminal is a cpu hog, especially when moved around.

glxgears is absolutly dependent on the cpu power.

everything that needs cpu, reduces glxgears numbers a lot.

add this points and you'll see that your behaviour is normal and not the fault of the nvidia driver
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Old 04-08-06, 05:53 PM   #4
mrmailer
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Default Re: even with 8756, minimal multitasking slows down glxgears performance

so tell me why any video, such as mythtv, mplayer, xine, etc, even with xvmc in use and low cpu used, has the same problems? i can't even browse the web with firefox while watching video in mythtv, etc.
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Old 04-08-06, 08:11 PM   #5
d13f00l
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Default Re: even with 8756, minimal multitasking slows down glxgears performance

Quote:
Originally Posted by mrmailer
so tell me why any video, such as mythtv, mplayer, xine, etc, even with xvmc in use and low cpu used, has the same problems? i can't even browse the web with firefox while watching video in mythtv, etc.
Because you're multitasking..it's going to slow anything down. Especially if the application has a sleep() in it
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Old 04-08-06, 08:31 PM   #6
kmare
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Default Re: even with 8756, minimal multitasking slows down glxgears performance

Quote:
Originally Posted by mrmailer
ok, here's glxgears on my geforce 6200. see if you can tell when i start doing something simple like moving gnome-terminal around

glxgears
5070 frames in 5.0 seconds = 1013.988 FPS
5013 frames in 5.0 seconds = 1002.463 FPS
4901 frames in 5.0 seconds = 980.162 FPS
3135 frames in 8.2 seconds = 383.096 FPS
173 frames in 5.8 seconds = 29.617 FPS


HELP
do you get ~1000 fps with glxgears even when you're not doing anything else? are you sure you have "direct rendering: yes"? what's your system spec? also please provide a nvidia-bug-report...
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Old 04-08-06, 10:47 PM   #7
d13f00l
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Default Re: even with 8756, minimal multitasking slows down glxgears performance

Quote:
Originally Posted by kmare
do you get ~1000 fps with glxgears even when you're not doing anything else? are you sure you have "direct rendering: yes"? what's your system spec? also please provide a nvidia-bug-report...

That's about right for that card, I think.
My Geforce 4mx 440 pulled over 4000, while my 6200 pulls a bit over 1000 generally.

As to why, I can't answer, but games are faster on this card than my MX.
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Old 04-08-06, 11:26 PM   #8
energyman76b
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Default Re: even with 8756, minimal multitasking slows down glxgears performance

Quote:
Originally Posted by mrmailer
so tell me why any video, such as mythtv, mplayer, xine, etc, even with xvmc in use and low cpu used, has the same problems? i can't even browse the web with firefox while watching video in mythtv, etc.
because you are not using XV?

Really, I can watch movies in xine/mplayer, browsethe web, have kmail open, mldonkey running and an emerge -and no skips, hangs or other problems. btw, I hardly believe that mythtv is really 'lightweight'.
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Old 04-13-06, 08:14 PM   #9
acoates
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Default Re: even with 8756, minimal multitasking slows down glxgears performance

Finally found someone with the same problem, apparently.

I'm using the 2.6.16-1.2080 kernel + 1.0-8178 drivers. Everything functions properly, however, any program that attempts to take over the CPU causes graphics performance to tank (e.g., glxgears drops to ~20 fps; any of my own GL apps to less than 5 fps). Compiling the following trivial program and running is sufficient to cause problems:

int main(int argc, char* argv[]) {
while (1) {
}
return 0;
}

This is not a "performance issue" as suggested by the above posts -- several other machines with inferior hardware handle the workloads without any difficulty (one running Mandrake 9, on a 1.2Ghz Athlon...). It appears to be some kind of multitasking issue.

Additional info:

Hardware is not my own; basically a Dell machine with GeForce Quadro2, P4 2.8Ghz, 1GB RAM. It's not the card performance -- it runs beautifully when multitasking is functioning properly (explained in the following).

Nicing the CPU-hogging process reduces the problem substantially. The un-niced process successfully causes graphics performance of GL apps (but not other graphics like console updates, firefox, etc.) to drop unreasonably (again, not the expected drop as a result of normal multitasking). Really, I have more faith in the Linux scheduler than this (unless they've reverted to coop multitasking and not told anyone...) In top, you can easily see the test app consuming 90+% of the CPU (with other processes happily receiving time; but the GL apps are starved). After nicing the process, it continues to use 90+% of the CPU, but the GL apps performance improves substantially and they receive an apparently "fair" share of the CPU budget (sufficient, at least, to maintain an acceptable frame rate).

The use of the glFlush() call appears to worsen the problem substantially. While I would expect this to reduce frame rates somewhat, its use in this case appears to stall the caller for as long as 100's of milliseconds.

I'd attach my "bug report" file, except that it exceeds the length allowed by the forum...
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Old 04-13-06, 08:26 PM   #10
netllama
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Default Re: even with 8756, minimal multitasking slows down glxgears performance

You can zip a bug report to attach it.

As others have noted, glxgears is a CPU bound application. Performance problems are to be expected. Are you seeing this behavior with anything other than glxgears and your own app? Can you post your own app here?

Thanks,
Lonni
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Old 04-13-06, 09:10 PM   #11
acoates
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Default Re: even with 8756, minimal multitasking slows down glxgears performance

My own app is no small creature, but it's certainly not a CPU guzzler. Basically, there's a piece of software that consumes a lot (though not all) of the CPU. Then there's a graphical front-end that renders data exported to it over an IPC pipe. The front-end spends most of its time blocked on the pipe and/or rendering frames (and these are pretty simple frames -- low hundreds of polys). On every other machine I've used this is fine -- MLFQS (or whatever Linux is using) gives the front-end and every other app a chunk of time, and the CPU-hog gets what's left (which is usually 90+% of the CPU). With FC5+Nvidia drivers, this is apparently not the case.

Even if GLXgears is CPU-bound, that's not a complete explanation for this level of performance drain. Two CPU-bound processes should run reasonably, if at reduced performance; it should never be the case that one "hungry" process completely wastes another process (and not just transiently, but permanently). The exact same experiment (with GlxGears) described in my first post yields completely reasonable behavior and performance changes on two other non-FC5 machines with poorer hardware. On the machine I'm presently using, for instance, the CPU use of GlxGears drops to ~30% when another hog is on the processor, but on the other machine (which has nearly equivalent hardware) GlxGears is completely trounced -- dropping from 98% usage to < 1%. X still appears to run fine, though, as every other application/window works smoothly without issue. It seems to be isolated to programs using OpenGL.

I suspect this is a bug or misconfiguration of the drivers on my part, or a strange FC5 kernel issue (in which case, I should probably go bark up another tree ) In any case, I've certainly come to expect performance losses as a result of multitasking -- but this is way way outside of normal. If this is "normal", I'm going back to QNX where "multitasking" really means you can do more than one thing at a time. lol

Thanks for reading; bug file attached.
AC

EDIT: apparently this other machine is 2.4Ghz; though that's still much faster than several others.
Attached Files
File Type: zip nvidia-bug-report.log.zip (24.0 KB, 122 views)
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Old 04-14-06, 12:59 AM   #12
Fackamato
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Default Re: even with 8756, minimal multitasking slows down glxgears performance

For what it's worth, with the composite extension enabled, a 6800GT and xorg 7, I get ~1000 fps in glxgears when I have xcompmgr -c running in the background. Quake 3 and 4 play fine though. (however I might be noticing some input lag in Quake 4 with xcompmgr, have to investigate further)
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