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-   -   MTRR support in recent driver/card? (http://www.nvnews.net/vbulletin/showthread.php?t=201289)

pigeon 02-02-13 10:42 PM

MTRR support in recent driver/card?
 
Hi,

I have a GTX 460 using the 310.19 driver.

I'm trying to use it without PAT support. I'm loading the nvidia kernel module driver with NVreg_UsePageAttributeTable=0

From the kernel messages I can see:

Code:

[  94.534963] NVRM: loading NVIDIA UNIX x86_64 Kernel Module  310.19  Thu Nov  8 00:52:03 PST 2012
[  94.535125] NVRM: builtin PAT support disabled, falling back to MTRRs.
[  126.927848] NVRM: GPU at 0000:01:00: GPU-2d2df840-6445-2af1-fc01-00f7c8346757

However, it doesn't seem to be using MTRR, at least I do not see any new MTRR entries in /proc/mtrr after the driver is loaded or after X has started. (I'm expecting to see some new write-combining MTRR region created)

And without PAT and MTRR, 3D performance is dreadful (3-4fps)

Is there something that can be done here?

Thanks.

brebs 02-03-13 05:15 AM

Re: MTRR support in recent driver/card?
 
Take a look:
Code:

cat /proc/mtrr
See if the kernel can fix it:
Code:

$ zgrep MTRR /proc/config.gz
CONFIG_MTRR=y
CONFIG_MTRR_SANITIZER=y
CONFIG_MTRR_SANITIZER_ENABLE_DEFAULT=1
CONFIG_MTRR_SANITIZER_SPARE_REG_NR_DEFAULT=1

Or try to fix it manually.

I dunno whether Option "IndirectMemoryAccess" "False" in xorg.conf would help.

Some other useful links:

http://www.nvnews.net/vbulletin/showthread.php?t=89781
http://www.tikirobot.net/wp/2009/03/...trrs-on-linux/
https://bbs.archlinux.org/viewtopic.php?id=91402

Why are you giving yourself this problem by not enabling PAT?

pigeon 02-03-13 07:23 AM

Re: MTRR support in recent driver/card?
 
Quote:

Originally Posted by brebs (Post 2585815)
Take a look:
Code:

cat /proc/mtrr
See if the kernel can fix it:
Code:

$ zgrep MTRR /proc/config.gz
CONFIG_MTRR=y
CONFIG_MTRR_SANITIZER=y
CONFIG_MTRR_SANITIZER_ENABLE_DEFAULT=1
CONFIG_MTRR_SANITIZER_SPARE_REG_NR_DEFAULT=1

Or try to fix it manually.

I already looked at those. I fixed it for my onboard intel graphics, but nvidia seems to be not using MTRR at all.

Quote:

Originally Posted by brebs (Post 2585815)
I dunno whether Option "IndirectMemoryAccess" "False" in xorg.conf would help.

Just tried, doesn't make a difference.

I have even tried manually adding the MTRR write-combining registers to match what the nvidia card is, but it just doesn't seem to be used.


Quote:

Originally Posted by brebs (Post 2585815)
Why are you giving yourself this problem by not enabling PAT?

I'm trying to use the nvidia card under Xen Dom0. The PAT support in the Xen Dom0 has some big issues and has been disabled. I ended up digging up some old MTRR Xen patches and seems to have got MTRR enabled in Dom0. Now the last step is to get nvidia to use MTRR.

And, yes yes, I know nvidia's driver + Xen has always been an issue for most non-Quadro cards. I'm just trying to do my best here. At least if I can see the nvidia drver is actually using MTRR then I'll be happy even if it doesn't boost the performance.

If someone from nvidia can confirm that MTRR is not being used anymore at all then that's also a good answer too.

Thanks for your suggestions too btw.


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