Re: amd64 + mtrr: only 3.1gb of 8gb are covered, kernel 2.6.30 and earlier.

[Yinghai Lu <yhlu.kernel@gmail.com>]

On Sat, Aug 22, 2009 at 11:54 AM, Volker Armin
Hemmann<volkerarmin@googlemail.com> wrote:
> On Samstag 22 August 2009, Yinghai Lu wrote:
>> On Fri, Aug 21, 2009 at 9:14 AM, Volker Armin
>>
>> Hemmann<volkerarmin@googlemail.com> wrote:
>> > Hi,
>> >
>> > I have an amd64 system with 8GB ram. Of these only 3.1GB are currently
>> > covered with mtrr:
>> > 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=0x0c0000000 ( 3072MB), size=  128MB, count=1: write-back
>> >
>> > This is with a Phenom II X4. Mobo is an Asrock A770Crossfire with AMD 770
>> > chipset. Ram is 1066 ddr2 running at 800.
>> >
>> > Before that I had a X2 6000 where I had one more mtrr, covering
>> > additional 256mb with 6gb ram total.
>> >
>> > When I use the opensource driver, I get a 'mtrr disabled' message when X
>> > starts, nothing like that with fglrx. The results are the same.
>> >
>> > Is there anything that I can do about it? I already played with mtrr
>> > cleanup options - without any results.
>> >
>> > Except for reiser4 the kernel is 'vanilla', config is attached, dmesg and
>> > lspci are folloiwing:
>> >
>> > dmesg:
>> > [    0.000000] Linux version 2.6.30.5r4 (root@energy) (gcc version 4.4.1
>> > (Gentoo 4.4.1 p1.0) ) #1 SMP Tue Aug 18 06:28:18 CEST 2009
>> > [    0.000000] Command line: root=/dev/md1
>> > md=3,/dev/sda3,/dev/sdb3,/dev/sdc3 nmi_watchdog=0 mtrr_spare_reg_nr=1
>> > [    0.000000] KERNEL supported cpus:
>> > [    0.000000]   Intel GenuineIntel
>> > [    0.000000]   AMD AuthenticAMD
>> > [    0.000000] BIOS-provided physical RAM map:
>> > [    0.000000]  BIOS-e820: 0000000000000000 - 000000000009fc00 (usable)
>> > [    0.000000]  BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)
>> > [    0.000000]  BIOS-e820: 00000000000e6000 - 0000000000100000 (reserved)
>> > [    0.000000]  BIOS-e820: 0000000000100000 - 00000000c7eb0000 (usable)
>> > [    0.000000]  BIOS-e820: 00000000c7eb0000 - 00000000c7ec0000 (ACPI
>> > data) [    0.000000]  BIOS-e820: 00000000c7ec0000 - 00000000c7ef0000
>> > (ACPI NVS) [    0.000000]  BIOS-e820: 00000000c7ef0000 - 00000000c7f00000
>> > (reserved) [    0.000000]  BIOS-e820: 00000000fff00000 - 0000000100000000
>> > (reserved) [    0.000000]  BIOS-e820: 0000000100000000 - 0000000238000000
>> > (usable) [    0.000000] DMI present.
>> > [    0.000000] AMI BIOS detected: BIOS may corrupt low RAM, working
>> > around it. [    0.000000] e820 update range: 0000000000000000 -
>> > 0000000000010000 (usable) ==> (reserved)
>> > [    0.000000] last_pfn = 0x238000 max_arch_pfn = 0x100000000
>> > [    0.000000] MTRR default type: uncachable
>> > [    0.000000] MTRR fixed ranges enabled:
>> > [    0.000000]   00000-9FFFF write-back
>> > [    0.000000]   A0000-EFFFF uncachable
>> > [    0.000000]   F0000-FFFFF write-protect
>> > [    0.000000] MTRR variable ranges enabled:
>> > [    0.000000]   0 base 000000000000 mask FFFF80000000 write-back
>> > [    0.000000]   1 base 000080000000 mask FFFFC0000000 write-back
>> > [    0.000000]   2 base 0000C0000000 mask FFFFF8000000 write-back
>> > [    0.000000]   3 disabled
>> > [    0.000000]   4 disabled
>> > [    0.000000]   5 disabled
>> > [    0.000000]   6 disabled
>> > [    0.000000]   7 disabled
>> > [    0.000000] TOM2: 0000000238000000 aka 9088M
>> > [    0.000000] x86 PAT enabled: cpu 0, old 0x7040600070406, new
>> > 0x7010600070106
>> > [    0.000000] e820 update range: 00000000c8000000 - 0000000100000000
>> > (usable) ==> (reserved)
>>
>> ...
>>
>> > 02:00.0 VGA compatible controller: ATI Technologies Inc Radeon HD 3870
>> > (prog- if 00 [VGA controller])
>> >        Subsystem: Info-Tek Corp. Device 4070
>> >        Flags: bus master, fast devsel, latency 0, IRQ 30
>> >        Memory at d0000000 (64-bit, prefetchable) [size=256M]
>> >        Memory at fdff0000 (64-bit, non-prefetchable) [size=64K]
>> >        I/O ports at b000 [size=256]
>> >        Expansion ROM at fdfc0000 [disabled] [size=128K]
>> >        Capabilities: [50] Power Management version 3
>> >        Capabilities: [58] Express Legacy Endpoint, MSI 00
>> >        Capabilities: [a0] MSI: Mask- 64bit+ Count=1/1 Enable+
>> >        Capabilities: [100] Vendor Specific Information <?>
>> >        Kernel driver in use: fglrx_pci
>> >        Kernel modules: fglrx
>>
>> after your start X server, how about cat /proc/mtrr?
>>
>> thought there should be one WC entry about 256M... for graphics card.
>>
>> YH
>
> running X:
>
> 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=0x0c0000000 ( 3072MB), size=  128MB, count=1: write-back
>
> back with my X2 6000 and 4 and 6gb ram, I indeed got another mtrr with 256mb.
> But with the phenom and 8gb I don't get it. Neither with fglrx nor with xorg's
> radeon driver. Radeon posts a message to dmesg about disabled mtrr.
>

you should have
reg03: base=0x0d0000000 ( 3200MB), size=  256MB, count=1: write-combining

do you notice any performance degrade without that entry?

YH