linux-kernel - Re: Missing MTRR ?

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Date:	Wed, 30 Sep 2009 14:34:08 -0700
From:	Yinghai Lu <yhlu.kernel@...il.com>
To:	J.A. Magallón <jamagallon@....com>
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Missing MTRR ?

On Wed, Sep 30, 2009 at 4:17 AM, J.A. Magallón <jamagallon@....com> wrote:
> Hi all...
>
> I'm using 2.6.31.1 on a box like this:
> - Intel(R) Core(TM)2 CPU 6420  @ 2.13GHz (dual core)
> - 4Gb RAM
>
> I find that MTRR setup is this:
> lorelei:/proc# cat mtrr
> reg00: base=0x0cff00000 ( 3327MB), size=    1MB, count=1: uncachable
> reg01: base=0x0d0000000 ( 3328MB), size=  256MB, count=1: uncachable
> reg02: base=0x0e0000000 ( 3584MB), size=  512MB, count=1: uncachable
> reg03: base=0x0cfea6000 ( 3326MB), size=    4KB, count=1: write-back
>
> I have no mtrr for my main memory, is this a problem for speed ?
>
> dmesg:
>
> BIOS-provided physical RAM map:
>  BIOS-e820: 0000000000000000 - 000000000008f000 (usable)
>  BIOS-e820: 000000000008f000 - 00000000000a0000 (reserved)
>  BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved)
>  BIOS-e820: 0000000000100000 - 00000000cee2a000 (usable)
>  BIOS-e820: 00000000cee2a000 - 00000000ceeb1000 (ACPI NVS)
>  BIOS-e820: 00000000ceeb1000 - 00000000cfe00000 (usable)
>  BIOS-e820: 00000000cfe00000 - 00000000cfe0d000 (reserved)
>  BIOS-e820: 00000000cfe0d000 - 00000000cfe94000 (usable)
>  BIOS-e820: 00000000cfe94000 - 00000000cfee9000 (ACPI NVS)
>  BIOS-e820: 00000000cfee9000 - 00000000cfeec000 (usable)
>  BIOS-e820: 00000000cfeec000 - 00000000cfef1000 (ACPI data)
>  BIOS-e820: 00000000cfef1000 - 00000000cfef2000 (usable)
>  BIOS-e820: 00000000cfef2000 - 00000000cfeff000 (ACPI data)
>  BIOS-e820: 00000000cfeff000 - 00000000cff00000 (usable)
>  BIOS-e820: 00000000cff00000 - 00000000d0000000 (reserved)
>  BIOS-e820: 00000000f0000000 - 00000000f8000000 (reserved)
>  BIOS-e820: 00000000fff00000 - 0000000100000000 (reserved)
>  BIOS-e820: 0000000100000000 - 000000012c000000 (usable)
> DMI 2.4 present.
> last_pfn = 0x12c000 max_arch_pfn = 0x400000000
> MTRR default type: write-back
> MTRR fixed ranges enabled:
>  00000-9FFFF write-back
>  A0000-FFFFF uncachable
> MTRR variable ranges enabled:
>  0 base 0CFF00000 mask FFFF00000 uncachable
>  1 base 0D0000000 mask FF0000000 uncachable
>  2 base 0E0000000 mask FE0000000 uncachable
>  3 base 0CFEA6000 mask FFFFFF000 write-back
>  4 disabled
>  5 disabled
>  6 disabled
>  7 disabled

interesting, the default type is write-back.

YH
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