Low performance on SuSE 10.1 x86_64

[ZicoTheTux]

Hi

Just installed SuSE 10.1 x86_64.
Compared to SuSE 10.0 (32 Bit) the dirver Performance is not even the half of what I had before (glxgreads drops from 17000 to 7500, games as well).
I use the newest nvidia driver (64Bit of course).
Tried all NvAGP settings.
dmesg keeps to tell me:
"NVRM: not using NVAGP, kernel was compiled with GART_IOMMU support!!"

Could this be a problem? If yes how to solve it?
I think it is a problem, because nvidia-settings tells me "Bus-Type: PCI", my GeForce 6800U is AGP model

zico@marvin:/proc/driver/nvidia/agp> cat /proc/driver/nvidia/agp/status
Status: Disabled

AGP initialization failed, please check the ouput
of the 'dmesg' command and/or your system log file
for additional information on this problem.


Looks bad. Is there a solution from the driver about that GART_IOMMU support or do I need to recompile the kernel?

[zander]

@ZicoTheTux: you'll need to rebuild your kernel without GART_IOMMU if you wish to use NvAGP (only one of these may drive the K8 GART); this isn't necessary with the Linux AGPGART driver.

[ZicoTheTux]

Ok but is there an alternative to NvAGP?
As far as I see there is completly no AGP support on the whole system.
I see I can't use NvAGP but as you read above everything runs on PCI-mode.
Ok it is not the drivers problem but has my kernel no AGP support at all or does it just not work with the nvidia driver?

[zander]

@ZicoTheTux: you can use the Linux AGPGART driver; this is the default configuration (i.e. if you leave the NvAGP X driver option unset or set it to "2").

[ZicoTheTux]

Tried now NvAGP 2 and removed the option.
In both cases the performance stays very low.

zico@marvin:/proc/driver/nvidia/agp> cat /proc/driver/nvidia/agp/status
Status: Disabled

stays there.
I tried to use testgart, a program to test agpgart on my system but it tells me
open: No such file or directory

The device
/dev/agpgart is not there, too.
Something seems to be wrong here

[zander]

@ZicoTheTux: make sure you configured your kernel to include AGPGART support; with respect to /dev/agpgart, it's not used by the NVIDIA graphics driver (the NVIDIA kernel module interfaces with agpgart.ko directly).

[ZicoTheTux]

Ok I now recompile the kernel with agpgar support.. I'm sure it will solve that problem.
So as I understand it now it will not be possible to run the nvidia driver at full performance without agpgart support in the kernel, right?
I always liked the suse default kernel because I could install everything very fast. This GART_IOMMU makes everything a bit more complicated and not very user friendly. I hope there will be a way in the future to solve this.

[zander]

@ZicoTheTux: the IOMMU/AGPGART code and NvAGP need to own the same resource, the K8 GART, in order to work; with IOMMU/AGPGART support built into Linux/x86-64 kernels, NvAGP support thus can't be enabled. If you don't need the IOMMU (i.e. if you don't have any devices that require 32-bit addressable DMA memory), you can safely disable GART_IOMMU and use NvAGP.

Older NVIDIA Linux graphics drivers relied on the IOMMU exclusively to obtain 32-bit addressable DMA memory mappings; as of 1.0-8756, the IOMMU will only be used on Linux/x86-64 kernels older than Linux 2.6.15, and only if the GPU for which the memory is allocated can't address memory past the 4GB boundary (NVIDIA non-legacy PCI-E GPUs can). On Linux/x86-64 kernels >= Linux 2.6.15, the GFP_DMA32 zone will be used instead, and IOMMU/SWIOTLB support won't even be built into the driver.

That said, the NVIDIA Linux/x86-64 graphics driver relies on AGPGART for AGP support if the kernel was built with IOMMU/AGPGART support; if the kernel was built with IOMMU support, but without AGPGART support, AGP support will be unavailable, which can incur a significant performance penalty, depending on the application(s) used.

[ZicoTheTux]

Ah I understand it now.
As question if we are at this theme:
As you said 32Bit Kernels will not make use of this feature. Would you personally suggest to install a 32 Bit system on an AGP-based 64Bit machine? I ask if I wonder if there could be any other "bottlenecks" within a 64Bit kernel/system interferring with AGP devices.

[zander]

@ZicoTheTux: no, it isn't necessary to install a 32-bit Linux kernel/system to take full advantage of the AGP port.

[ZicoTheTux]

Ok I now finally had the time to recompile the kernel and played a bit around with the 32Bit version.
It works for NvAGP finally.
But I notice a performance drop since i upgraded from 8174 to 8756.
glxgears dropped from 16000 to 13000 and in my games I lost about 10 FPS (average). I wonder why this happens.
I tried a bit around by disbaling PREEMPT in the kernel, switching NvAGP modes and made sure FSAA and FSAF is disabled. But I still notice this Framedrop.

Here an example:
CPU: AMD64 3500+
Video: GeForce 6800Ultra

SuSE10 (32Bit), nvidia-8174, Doom3 timedemo usechache - Ultra details: 82FPS
SuSE10.1 (64Bit), nvidia-8756, Doom3 timedemo usechache - Ultra details: 72FPS
SuSE10.1 (32Bit), nvidia-8756, Doom3 timedemo usechache - Ultra details: 69FPS
strange