Re: [PATCH] LZMA support in i386-pc kernel

[Vesa Jääskeläinen]

Bean wrote:
> Hi,
>
> This patch add support for lzma decompression. The assembly code
> lzma_decode.S is manually optimized to reduce size. The result decoder
> is tiny, only 416 bytes longer than the lzo version.

Not bad.

> I also include lzma encode from the LZMA SDK. grub needs to use the
> ANSI-C version of encoder, which is only present in the latest 4.58
> beta. I can't find ready to use shared library in most distro.
> Including the encoder/decoder has advantages as well. We don't need to
> worry about the host os, and lzma encoder/decoder can be used in other
> place, like font compression.

We can load more complete decoder module after we can load modules and 
leave more optimized version in boot code.

> I use lzma as default, it's still possible to use the old lzo
> compression, you just need to add --enable-lzo option when running
> configure.
>
> PS, here are some information about the lzma decoder:
>
> properties: lc = 3 lp = 0 pb = 2
> memory requirement for the decoder: 15980 bytes

Can we probe for best values and then use always the best? Perhaps embed 
them as constants to boot code?

> Result of
> ./grub-mkimage -o core.img biosdisk pc ext2 lvm raid
>
> lzma version: 27,776 bytes
> lzo version: 32,768 bytes

Not bad. Not bad at all.