[coreboot] Upgrade the 12 years old LZMA libraries - should we do it?

[Carl-Daniel Hailfinger]

Hi Ivan,

On 03.04.2018 20:03, Ivan Ivanov wrote:
> I have noticed that both coreboot and seabios are using the very old
> versions of LZMA SDK.

True. I introduced the lzma code in coreboot (back when it was called
LinuxBIOS) when we were working on OLPC XO-1 support.


> If we will upgrade our LZMA libraries from the
> outdated-by-12-years 4.42 to the current version 18.04 , speed and
> compression ratio should improve and maybe a few bugs will be fixed.

Do you have any numbers for this? An improved compression ratio and
improved speed would be nice indeed, but how does the size of the
decompression code change? If the decompression code grows more than the
size reduction from better compression, it would be a net loss. A
significantly reduced decompression speed would also be a problem.
Decompression speed would have to be measured both for stream
decompression (i.e. the decompressor gets the compressed data in
single-byte or multibyte chunks) as well as full-size decompression
(i.e. the decompressor can access all compressed data at once). We also
have to make sure that stream decompression still works after the change.


> Do you think it should be done, or you are OK with using such an
> outdated version?

A size benefit for the resulting image is a good reason to switch.

Regards,
Carl-Daniel