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Lebkoungcity
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PostPosted: Sat Feb 16, 2019 10:20 am    Post subject: nvidia-drivers and MTRR [satisfactory answers] Reply with quote

Hello,

like the topic says: I'm confused by articles on wiki.gentoo.org, namely https://wiki.gentoo.org/wiki/NVidia/nvidia-drivers and https://wiki.gentoo.org/wiki/MTRR_and_PAT.

There is a nvidia-card in my machine and I use nvidia-drivers. Occasionally KDE/Plasma tells me that some part crashed (e.g. kwin) and was restarted or that hardware graphics acceleration was stopped and was replaced by software graphics acceleration. This is a behavior I see for some years now and from time to time I try to solve it - without success to this moment.

One thing I found some time ago was that the output of
Code:
cat /proc/mtrr
was not optimal, there were lots of lines saying 'uncachable'.

And this is when my confusion started:
I looked into the BIOS like recommended here: https://wiki.gentoo.org/wiki/NVidia/nvidia-drivers#Getting_2D_acceleration_to_work_on_machines_with_4GB_memory_or_more but found no entry I could set from 'continuous' to 'discrete' (or something similar). So I read https://wiki.gentoo.org/wiki/MTRR_and_PAT and changed the kernel config to this:
Quote:

-*- MTRR (Memory Type Range Register) support │ │
│ │ [*] MTRR cleanup support │ │
│ │ (1) MTRR cleanup enable value (0-1) │ │
│ │ (1) MTRR cleanup spare reg num (0-7)

Now I have this:
Code:
 # cat /proc/mtrr
reg00: base=0x000000000 (    0MB), size= 2048MB, count=1: write-back
reg01: base=0x080000000 ( 2048MB), size= 1024MB, count=1: write-back
reg02: base=0x0bfe00000 ( 3070MB), size=    2MB, count=1: uncachable


So now, what to do next?

To complete my infos a bit more, some specs of this machine:
Quote:
description: Motherboard
product: GA-MA770T-UD3
vendor: Gigabyte Technology Co., Ltd.

description: BIOS
vendor: Award Software International, Inc.
physical id: 0
version: F7
date: 07/09/2010

description: CPU
product: AMD Athlon(tm) II X2 260 Processor
vendor: Advanced Micro Devices [AMD]
physical id: 4
bus info: cpu@0
version: AMD Athlon(tm) II X2 260 Processor
slot: Socket M2
size: 1900MHz
capacity: 3200MHz
width: 64 bits
clock: 200MHz
capabilities: fpu fpu_exception wp vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp x86-64 3dnowext 3dnow constant_tsc rep_good nopl nonstop_tsc cpuid extd_apicid pni monitor cx16 popcnt lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs skinit wdt hw_pstate vmmcall npt lbrv svm_lock nrip_save cpufreq

description: VGA compatible controller
product: GM107 [GeForce GTX 750]
vendor: NVIDIA Corporation
physical id: 0
bus info: pci@0000:01:00.0
version: a2
width: 64 bits
clock: 33MHz
capabilities: pm msi pciexpress vga_controller bus_master cap_list rom
configuration: driver=nvidia latency=0
resources: irq:28 memory:fb000000-fbffffff memory:c0000000-cfffffff memory:de000000-dfffffff ioport:ef00(size=128) memory:c0000-dffff


Thanks a lot for your attention!
Andy
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Last edited by Lebkoungcity on Sun Feb 17, 2019 5:56 pm; edited 1 time in total
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PostPosted: Sat Feb 16, 2019 11:30 am    Post subject: Reply with quote

Lebkoungcity,

Code:
# cat /proc/mtrr
reg00: base=0x000000000 (    0MB), size= 2048MB, count=1: write-back
reg01: base=0x080000000 ( 2048MB), size= 1024MB, count=1: write-back
reg02: base=0x0bfe00000 ( 3070MB), size=    2MB, count=1: uncachable


That all looks good. write-back, is correct. That's most of your RAM.
If you had write-through, you get read caching only. Writes update both the cache and main RAM at the speed of main RAM.

That 2MB uncachable close to the top of the first 4G of address space is probably PCI hardware registers that can be changed by hardware.
Its a really bad idea to try to cache hardware registers. There is usually no way to keep the cache synchronised.

How much RAM do you have?
If all your RAM is covered by write-back cache, you are good.
Its not always easy to tell, since physical RAM can be mapped around the PCI hardware address space.

If you have 16G RAM fitted, you have a problem. If you have 4G RAM, you might be able to do better. If you have 3G RAM, it looks good.
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Lebkoungcity
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PostPosted: Sat Feb 16, 2019 4:00 pm    Post subject: Reply with quote

NeddySeagoon wrote:
(...) If you have 4G RAM, you might be able to do better.(...)


Hi NeddySeagoon,

it's always a pleasure to read your posts, thank you :)

I have 4G RAM, it looks like this:
Code:
 # cat /proc/meminfo
MemTotal:        4041668 kB
MemFree:          761240 kB
MemAvailable:    3575924 kB
Buffers:          621688 kB
Cached:          1788476 kB
SwapCached:           40 kB
Active:          2045752 kB
Inactive:         594852 kB
Active(anon):     117160 kB
Inactive(anon):   120876 kB
Active(file):    1928592 kB
Inactive(file):   473976 kB
Unevictable:        8448 kB
Mlocked:            8448 kB
SwapTotal:       5253248 kB
SwapFree:        5252728 kB
Dirty:                76 kB
Writeback:             0 kB
AnonPages:        238968 kB
Mapped:           149484 kB
Shmem:               672 kB
Slab:             515852 kB
SReclaimable:     468480 kB
SUnreclaim:        47372 kB
KernelStack:        2544 kB
PageTables:         6088 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:     7274080 kB
Committed_AS:     653104 kB
VmallocTotal:   34359738367 kB
VmallocUsed:           0 kB
VmallocChunk:          0 kB
Percpu:             1952 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
Hugetlb:               0 kB
DirectMap4k:      190400 kB
DirectMap2M:     4001792 kB
DirectMap1G:     2097152 kB


How could I do better? To me it's unclear wheat it means with this cached/uncached/write-back/... memory. I do understand the words but the meaning is uncertain to me...

Greetings,
Andy
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PostPosted: Sat Feb 16, 2019 4:56 pm    Post subject: Reply with quote

Lebkoungcity,

Can you pastebin dmesg please?
We need it all, especially the BIOS provided memory map at the start.

I say "might be able to do better" because it depends on your hardware and your install.
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PostPosted: Sat Feb 16, 2019 5:00 pm    Post subject: Reply with quote

Here is some discussion about it.
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PostPosted: Sat Feb 16, 2019 5:16 pm    Post subject: Reply with quote

NeddySeagoon wrote:

Can you pastebin dmesg please?


Sure, here it is:
https://pastebin.com/xKP5J1s3
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PostPosted: Sat Feb 16, 2019 5:17 pm    Post subject: Reply with quote

Jaglover wrote:
Here is some discussion about it.


Thank you! Seems I'm not the only one who doesn't understand it fully :lol:
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PostPosted: Sat Feb 16, 2019 5:48 pm    Post subject: Reply with quote

Direct MTRR use by drivers on Linux is now completely phased out ...
Go figure, it was written in 2015.
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PostPosted: Sat Feb 16, 2019 6:02 pm    Post subject: Reply with quote

I have (nearly) the same motherboard, but 6GB RAM and amdgpu. No crash problems here.
paste /sys/class/dmi/id/{board,bios}_*:

GA-MA770-UD3            Gigabyte Technology Co., Ltd.   x.x     11/19/2009      Award Software International, Inc.      FGc

Neither the MTRR nor PAT ranges fully cover RAM, but I don't see any obvious ill effects:
cat /proc/mtrr /sys/kernel/debug/x86/pat_memtype_list:
reg00: base=0x000000000 (    0MB), size= 2048MB, count=1: write-back
reg01: base=0x080000000 ( 2048MB), size=  512MB, count=1: write-back
reg02: base=0x0a0000000 ( 2560MB), size=  256MB, count=1: write-back
reg03: base=0x0afe00000 ( 2814MB), size=    2MB, count=1: uncachable
PAT memtype list:
write-back @ 0xafde0000-0xafde1000
write-back @ 0xafde3000-0xafdeb000
write-back @ 0xafde3000-0xafde4000
write-back @ 0xafdea000-0xafdec000
write-combining @ 0xb0000000-0xc0000000
write-combining @ 0xb0000000-0xc0000000
uncached-minus @ 0xcfe00000-0xcfe01000
uncached-minus @ 0xe0000000-0xf0000000
uncached-minus @ 0xe00a0000-0xe00a1000
uncached-minus @ 0xfde80000-0xfdec0000
uncached-minus @ 0xfdefc000-0xfdf00000
uncached-minus @ 0xfdfe0000-0xfdfe1000
uncached-minus @ 0xfdfff000-0xfe000000
uncached-minus @ 0xfe028000-0xfe029000
uncached-minus @ 0xfe029000-0xfe02a000
uncached-minus @ 0xfe02a000-0xfe02b000
uncached-minus @ 0xfe02b000-0xfe02c000
uncached-minus @ 0xfe02c000-0xfe02d000
uncached-minus @ 0xfe02d000-0xfe02e000
uncached-minus @ 0xfe02e000-0xfe02f000
uncached-minus @ 0xfe02f000-0xfe030000
uncached-minus @ 0xfed00000-0xfed01000
for i in /sys/firmware/memmap/*; do paste $i/{start,end,type}; done | column -ts $'\t' -R 1,2:
        0x0      0x983ff  System RAM
    0x98400      0x9ffff  Reserved
    0xf0000      0xfffff  Reserved
   0x100000   0xafd80fff  System RAM
 0xafde0000   0xafde2fff  ACPI Non-volatile Storage
 0xafde3000   0xafdeffff  ACPI Tables
 0xafdf0000   0xafdfffff  Reserved
 0xe0000000   0xefffffff  Reserved
 0xfec00000   0xffffffff  Reserved
0x100000000  0x1cfffffff  System RAM
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PostPosted: Sat Feb 16, 2019 6:14 pm    Post subject: Reply with quote

Lebkoungcity,

Lets start with
Code:
[    0.000000] BIOS-provided physical RAM map:
[    0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009f7ff] usable
[    0.000000] BIOS-e820: [mem 0x000000000009f800-0x000000000009ffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved
[    0.000000] BIOS-e820: [mem 0x0000000000100000-0x00000000bfdeffff] usable
[    0.000000] BIOS-e820: [mem 0x00000000bfdf0000-0x00000000bfdf2fff] ACPI NVS
[    0.000000] BIOS-e820: [mem 0x00000000bfdf3000-0x00000000bfdfffff] ACPI data
[    0.000000] BIOS-e820: [mem 0x00000000bfe00000-0x00000000bfefffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000e0000000-0x00000000efffffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000fec00000-0x00000000ffffffff] reserved
[    0.000000] BIOS-e820: [mem 0x0000000100000000-0x000000013fffffff] usable

Even today, your CPU starts up in 16 bit real mode and fetches its start address from 0xfff0, just like the original 8086. Keep that in mind.
Code:
[    0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009f7ff] usable
[    0.000000] BIOS-e820: [mem 0x000000000009f800-0x000000000009ffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved
is the real mode address space.
The first line is the bottom 640kB, of which Bill Gates famously said, 640k of RAM is enough for anybody.
The reserved regions following are for BIOS expansion ROMs. You can't write there, but read caching works. Some expansion cards, like video cards expose the pixel buffer there too, so it might not all be ROM.

Once you get out of real mode into protected mode, the above still applies and you get
Code:
[    0.000000] BIOS-e820: [mem 0x0000000000100000-0x00000000bfdeffff] usable
[    0.000000] BIOS-e820: [mem 0x00000000bfdf0000-0x00000000bfdf2fff] ACPI NVS
[    0.000000] BIOS-e820: [mem 0x00000000bfdf3000-0x00000000bfdfffff] ACPI data
[    0.000000] BIOS-e820: [mem 0x00000000bfe00000-0x00000000bfefffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000e0000000-0x00000000efffffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000fec00000-0x00000000ffffffff] reserved

The first is real RAM above 1MiB, you have 640k below 1MiB too, so its not contiguous. There is a hole from 640k to 1M for peripherals to do what they want. That's for ISA cards.
You don't actually have any plug in ISA cards but some are still there.
The rest are for ROM of one sort or another, PCI hardware address space, the BIOS that's also at 0xf0000. The PC is really quite a house of cards.
[mem 0x0000000000100000-0x00000000bfdeffff] is about 3G of RAM. 4G would be 0x0 to 0xffffffff. But then there is nowhere for the BIOS, video card, expansion ROM and the other memory mapped devices.
This is the problem with 4G of RAM and a 32 bit install. You don't get all 4G mapped into the address space at the same time.

The last entry is
Code:
[    0.000000] BIOS-e820: [mem 0x0000000100000000-0x000000013fffffff] usable

That's your entire 4G RAM mapped into the address space at the 4G boundary. A 32 bit install or 32 bit hardware can't do that.

I would expect all that 4G to be write-back or write-combining but it looks like its the 3G starting at 1M that's write-back cached.
Its the same physical RAM that appears in the memory map several times.

-- edit --
Here's your PCI memory mapped region.
Code:
[    0.043790] [mem 0xbff00000-0xdfffffff] available for PCI devices


You have 64Mb of RAM hidden under hardware.
Code:
[    0.162934] AGP: Your BIOS doesn't leave an aperture memory hole
[    0.162934] AGP: Please enable the IOMMU option in the BIOS setup
[    0.162935] AGP: This costs you 64MB of RAM
[    0.162937] AGP: Mapping aperture over RAM [mem 0xb4000000-0xb7ffffff] (65536KB)

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Lebkoungcity
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PostPosted: Sun Feb 17, 2019 10:07 am    Post subject: Reply with quote

NeddySeagoon,

wow, thank you for your detailed post! It's amazing how you put these things in easy-to-understand-words even for non-native-speakers like me!

So, there's not really something for me to do regarding memory? OK, as long as it works it's fine for me :)

Does it also apply to this?
NeddySeagoon wrote:

You have 64Mb of RAM hidden under hardware.
Code:
[    0.162934] AGP: Your BIOS doesn't leave an aperture memory hole
[    0.162934] AGP: Please enable the IOMMU option in the BIOS setup
[    0.162935] AGP: This costs you 64MB of RAM
[    0.162937] AGP: Mapping aperture over RAM [mem 0xb4000000-0xb7ffffff] (65536KB)

In the kernel's config everything concerning AGP is disabled and in the BIOS I can't find an entry saying IOMMU... Does this mean it's OK the way it is?

Cheers,
Andy
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PostPosted: Sun Feb 17, 2019 10:11 am    Post subject: Reply with quote

Do you need IOMMU? To my knowledge it shouldn't be turned on in vain as it may add a little overhead.
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PostPosted: Sun Feb 17, 2019 10:12 am    Post subject: Reply with quote

Ant P. wrote:
I have (nearly) the same motherboard, but 6GB RAM and amdgpu. No crash problems here.
(...)


Ant P.,

thank you for your input! On my machine it looks similar:
Code:
 # paste /sys/class/dmi/id/{board,bios}_*
GA-MA770T-UD3           Gigabyte Technology Co., Ltd.   x.x     07/09/2010      Award Software International, Inc.     F7


Code:
 # cat /proc/mtrr /sys/kernel/debug/x86/pat_memtype_list
reg00: base=0x000000000 (    0MB), size= 2048MB, count=1: write-back
reg01: base=0x080000000 ( 2048MB), size= 1024MB, count=1: write-back
reg02: base=0x0bfe00000 ( 3070MB), size=    2MB, count=1: uncachable
PAT memtype list:
write-back @ 0xbfdf0000-0xbfdf1000
write-back @ 0xbfdf3000-0xbfdfb000
write-back @ 0xbfdf3000-0xbfdf4000
write-back @ 0xbfdfa000-0xbfdfc000
write-combining @ 0xc0000000-0xc0005000
write-combining @ 0xc0020000-0xc0025000
write-combining @ 0xc0040000-0xc0045000
write-combining @ 0xc0060000-0xc0065000
write-combining @ 0xc0080000-0xc0085000
write-combining @ 0xc00a0000-0xc00a5000
write-combining @ 0xc00c0000-0xc00c5000
write-combining @ 0xc00e0000-0xc00e5000
write-combining @ 0xc0100000-0xc0105000
write-combining @ 0xc0120000-0xc0125000
write-combining @ 0xc0140000-0xc0145000
write-combining @ 0xc0160000-0xc0165000
write-combining @ 0xc0180000-0xc0181000
write-combining @ 0xc01a0000-0xc01a1000
write-combining @ 0xc01c0000-0xc01c1000
write-combining @ 0xc01e0000-0xc0220000
write-combining @ 0xc0220000-0xc0221000
write-combining @ 0xc0240000-0xc0241000
write-combining @ 0xc0260000-0xc0262000
write-combining @ 0xc0280000-0xc0281000
write-combining @ 0xc02a0000-0xc02c0000
write-combining @ 0xc02c0000-0xc02e0000
write-combining @ 0xc02e0000-0xc0300000
write-combining @ 0xc0300000-0xc0320000
uncached-minus @ 0xcfee0000-0xcfee1000
uncached-minus @ 0xcfee0000-0xcfee1000
uncached-minus @ 0xcfee0000-0xcffe0000
uncached-minus @ 0xcfee1000-0xcfee2000
uncached-minus @ 0xcfee1000-0xcfee2000
uncached-minus @ 0xcfee2000-0xcfee3000
uncached-minus @ 0xcfee2000-0xcfee3000
uncached-minus @ 0xcfee2000-0xcfee3000
uncached-minus @ 0xcfee2000-0xcfee3000
write-combining @ 0xde000000-0xdf000000
uncached-minus @ 0xe0000000-0xf0000000
uncached-minus @ 0xe0010000-0xe0011000
uncached-minus @ 0xe00a0000-0xe00a1000
uncached-minus @ 0xe0100000-0xe0101000
uncached-minus @ 0xfb000000-0xfc000000
uncached-minus @ 0xfcffc000-0xfd000000
uncached-minus @ 0xfdafe000-0xfdb00000
uncached-minus @ 0xfdaff000-0xfdb00000
uncached-minus @ 0xfddf8000-0xfddf9000
uncached-minus @ 0xfddff000-0xfde00000
uncached-minus @ 0xfe024000-0xfe028000
uncached-minus @ 0xfe028000-0xfe029000
uncached-minus @ 0xfe029000-0xfe02a000
uncached-minus @ 0xfe02a000-0xfe02b000
uncached-minus @ 0xfe02b000-0xfe02c000
uncached-minus @ 0xfe02c000-0xfe02d000
uncached-minus @ 0xfe02d000-0xfe02e000
uncached-minus @ 0xfe02e000-0xfe02f000
uncached-minus @ 0xfe02f000-0xfe030000
uncached-minus @ 0xfed00000-0xfed01000


Code:
 # for i in /sys/firmware/memmap/*; do paste $i/{start,end,type}; done | column -ts $'\t' -R 1,2        0x0      0x9f7ff  System RAM
    0x9f800      0x9ffff  Reserved
    0xf0000      0xfffff  Reserved
   0x100000   0xbfdeffff  System RAM
 0xbfdf0000   0xbfdf2fff  ACPI Non-volatile Storage
 0xbfdf3000   0xbfdfffff  ACPI Tables
 0xbfe00000   0xbfefffff  Reserved
 0xe0000000   0xefffffff  Reserved
 0xfec00000   0xffffffff  Reserved
0x100000000  0x13fffffff  System RAM


So I think these 'hiccups' with Plasma are one of those things I just have to live with. Something slightly annoying but not that big issue.

Cheers,
Andy
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PostPosted: Sun Feb 17, 2019 10:18 am    Post subject: Reply with quote

Jaglover wrote:
Do you need IOMMU? To my knowledge it shouldn't be turned on in vain as it may add a little overhead.


To be honest: I'm not sure :wink: But after this thread I think I don't need it. I was just looking into this memory/MTRR stuff because I thought, it would be worth to know if it was a problem (and if it was to solve it).

Cheers,
Andy
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NeddySeagoon
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Joined: 05 Jul 2003
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PostPosted: Sun Feb 17, 2019 10:47 am    Post subject: Reply with quote

Lebkoungcity,

I lose 64Mb RAM like that too and I don't have a IOMMU option in my BIOS.
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Computer users fall into two groups:-
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Lebkoungcity
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Joined: 16 Nov 2008
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PostPosted: Sun Feb 17, 2019 5:54 pm    Post subject: Reply with quote

Now that I know my machine is OK I close this thread. Thank you all for your assistance!
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