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

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Message-ID: <86802c440908270013k4b8c75b1h6bac33a623ded5e7@mail.gmail.com>
Date:	Thu, 27 Aug 2009 00:13:48 -0700
From:	Yinghai Lu <yhlu.kernel@...il.com>
To:	Volker Armin Hemmann <volkerarmin@...glemail.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: amd64 + mtrr: only 3.1gb of 8gb are covered, kernel 2.6.30 and 
	earlier.

On Wed, Aug 26, 2009 at 6:13 PM, Volker Armin
Hemmann<volkerarmin@...glemail.com> wrote:
> Hi,
>
> On Sonntag 23 August 2009, Yinghai Lu wrote:
>> On Sat, Aug 22, 2009 at 12:26 PM, Volker Armin
>>
>> Hemmann<volkerarmin@...glemail.com> wrote:
>> > when I went from 4gb to 6gb I had a performance degradation. Since the
>> > 8gb are faster and the new cpu is faster, I don't see degradation. But I
>> > wonder how much better performance could be with 'correct' mtrr.
>>
>> that is weird. with 4g should have mem hole remapping.
>>
>> do you still have /proc/mtrr for 6g setup?
>>
>> YH
>
> some more information, mtrr of 8gb with my X2 6000:
>
> 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
> reg03: base=0x0c8000000 ( 3200MB), size=   64MB, count=1: write-back
> reg04: base=0x0cc000000 ( 3264MB), size=   32MB, count=1: write-back
> reg05: base=0x0ce000000 ( 3296MB), size=   16MB, count=1: write-back
>
> from June with 2.6.30, dmesg from that incident is attached
>
> compared that with the mtrr with my X4:
>
> 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
>
>
> just ignore the fgrlx parts - whenever I checked it did not made a difference
> if X was started or not.
>

theo one with X4, you got extra device

[    0.383812] pci 0000:03:00.0: reg 10 io port: [0xd800-0xd8ff]
[    0.383828] pci 0000:03:00.0: reg 18 64bit mmio: [0xfebff000-0xfebfffff]
[    0.383844] pci 0000:03:00.0: reg 30 32bit mmio: [0xfebc0000-0xfebdffff]
[    0.383878] pci 0000:03:00.0: supports D1 D2
[    0.383879] pci 0000:03:00.0: PME# supported from D1 D2 D3hot D3cold
[    0.383916] pci 0000:03:00.0: PME# disabled

so BIOS allocate more mmio space for it.

YH
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