[coreboot] [PATCH] Add option 'compress ramstage'

Eric W. Biederman ebiederm at xmission.com
Mon May 2 22:00:29 CEST 2011


Sven Schnelle <svens at stackframe.org> writes:

> Add an option to make compression of ramstage configurable. Right now
> it is always compressed. On my Thinkpad, the complete boot to grub takes
> 4s, with around 1s required for decompressing ramstage. This is probably
> caused by the fact the decompression does a lot of single byte/word/qword
> accesses, which are really slow on SPI buses. So give the user the option
> to store ramstage uncompressed, if he has enough memory.

Odd. Historically this has been solved by simply putting an mtrr over
the compressed area.  So that you would still get full cache block
transfers during the decompression.  I am fuzzy about the appropriate
mode.  Write protect I think.

Have you tried setting up an mtrr over the area that will be
decompressed.  That should result in something that is even faster
than copying non-compressed data.

Eric




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