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-   -   latency problems with binary nvidia drivers (http://www.nvnews.net/vbulletin/showthread.php?t=78279)

RobotMarvin 10-16-06 03:06 AM

latency problems with binary nvidia drivers
Hello everyone.

I have run into the following problem: when using the binary only nvidia drivers, some part of the nvidia driver seems to hold its interrupt for too long when switching between Xorg and the VT (console) because I get buffer underruns with my DVB-C card. This is even worse with the new beta drivers.

I just tried the Xorg supplied nv driver and no matter what I do, everything works perfectly in that respect. I can put as much load on the machine as I want and do as much switching as possible, no buffer underruns at all.

Now I wanted to bring this up to the nvidia devs but I guess having it posted here first is the preferred way. :-)

System: Athlon64 3500+ (S. 939), Leadtek PX6600 GT Extreme (PCIe), nforce4 ultra based board, Xorg 7.1 (Gentoo ~amd64 64bit system).

I have suspected the nvidia drivers of this behavior earlier (a year ago or so) because of a "lost interrupts" problem I was having. Back then I didn't have the time to investigate this any further- besides, I found acceptable workarounds. Today, the workarounds are no longer needed because that problem seems to be fixed. (either with the drivers or with the kernel)

Thanks in advance for any hints or help!

netllama 10-16-06 11:47 AM

Re: latency problems with binary nvidia drivers
If this problem reproduces with 1.0-9626, please generate and attach an nvidia-bug-report.log while the problem is present.


RobotMarvin 10-19-06 12:54 PM

Re: latency problems with binary nvidia drivers
1 Attachment(s)
Ok, attached. :)

Also heavily crosstested the open source nv driver again- no matter what I do, it's not reproducable there. Works just fine.

Also disabled PAT and put a quick&dirty return 0 in nv_flush_cashes() (which supposedly has a high latency problem) for a test: without any improvement.

The attached log is with vanilla nvidia drivers (except for a 2.6.19rc2 compile fix).

netllama 10-19-06 02:42 PM

Re: latency problems with binary nvidia drivers
Was this bug report generated while the problem was present?
Have you verified that you're using the latest BIOS for the motherboard?
Does this problem also reproduce with a 2.6.18.x kernel.org kernel?


RobotMarvin 10-22-06 05:36 PM

Re: latency problems with binary nvidia drivers
After some more tests I must admit that this problem is not reproducable in a vanilla kernel. The only thing that jumped to my mind was that a <.19 kernel always assigned high irq numbers (range from 50-70) to both the dvb-c and the 6600 gt card. With the current 2.6.19rc2, both usually end up at 16 for the dvb-c and 18 for the 6600 gt.

I will investigate this further... and keep it posted here.

RobotMarvin 10-27-06 10:40 AM

Re: latency problems with binary nvidia drivers
Unfortunately I cannot get this problem resolved. I checked the following things without any luck:

- no or full preemption
- pci=nommconf,nomsi,routeirq (...)
- noapic
- nolapic
- experimented with new 2.6.19 options (e.g. CONFIG_HT_IRQ)

No matter what I do: a few Xorg <-> VT switches already result in buffer underruns with my DVB card. The open source nv driver instead works just fine... no matter what I do, I am unable to force a underrun.

This really points to the nvidia driver. Is there anything I can do to help identify and fix this problem?

Thanks again...

RobotMarvin 11-24-06 08:11 AM

Re: latency problems with binary nvidia drivers
Ok... the problem still exists with 1.0.9742 and kernel 2.6.19-rc6-git2. This is rather annoying. I'd really appreciate it if this could get some attention. Isn't there anything I can do to assist in identifying what's going wrong?

chrisle 11-25-06 08:43 AM

Re: latency problems with binary nvidia drivers

I also have a problem but dont know if its the same.
Can you try to run the game nexuiz.
When I run this game it stutters and sometimes stops and when i then switch with ctrl alt f1 to console it sometimes starts working again.
I have an old P3 system with an AGP GeForce 6200.

Thanks chris.

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