x86_32: trim memory by updating e820

when MTRRs are not covering the whole e820 table, we need to trim the
RAM and need to update e820.

reuse some code on 64-bit as well.

here need to add early_get_cap and use it in early_cpu_detect, and move
mtrr_bp_init early.

The code successfully trimmed the memory map on Justin's system:

from:

 [    0.000000]  BIOS-e820: 0000000100000000 - 000000022c000000 (usable)

to:

 [    0.000000]   modified: 0000000100000000 - 0000000228000000 (usable)
 [    0.000000]   modified: 0000000228000000 - 000000022c000000 (reserved)

According to Justin it makes quite a difference:

|  When I boot the box without any trimming it acts like a 286 or 386,
|  takes about 10 minutes to boot (using raptor disks).

Signed-off-by: Yinghai Lu <[email protected]>
Tested-by: Justin Piszcz <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
This commit is contained in:
Yinghai Lu 2008-01-30 13:33:32 +01:00 • committed by Ingo Molnar
commit 093af8d7f0
6 changed files with 64 additions and 10 deletions

View file

@ -583,7 +583,7 @@ and is between 256 and 4096 characters. It is defined in the file
See drivers/char/README.epca and
Documentation/digiepca.txt.
disable_mtrr_trim [X86-64, Intel only]
disable_mtrr_trim [X86, Intel and AMD only]
By default the kernel will trim any uncacheable
memory out of your available memory pool based on
MTRR settings. This parameter disables that behavior,