This adds zstd support to cbfstool. The code is taken from zstd-1.5.7
with modifications:
- renaming bits.h to zstd_bits.h to avoid conflicts with coreboot's
bits.h used on riscv
- renaming compiler.h to zstd_compiler.h to avoid conflicts with
coreboot's compiler.h
- Dropped all streaming API functions
- Dropped multithreaded support, since it's now unused
- Dropped local DDict support
zstd offers similar compression ratios to LZMA, but a vastly fast
decompress speed. Typically zstd results in slightly larger binaries
than LZMA. Whether zstd should then be preferred over LZMA depends on
a few things:
- Caching: When loading from memory mapped boot devices, zstd will read
the boot medium multiple times, while LZMA will not. If the memory
mapped boot medium is not cached zstd results in much slower
decompression.
- Boot medium speed: Often, but not always LZMA results in smaller
binaries. If the boot medium is the bottleneck, than loading smaller
binaries might actually be faster. On a fast boot medium (high spi
freq, using quad/dual io), the performance benefits from zstd might be
more substantial
- zstd decompression code has a much larger footprint than LZMA. If the
stage (postcar) is loaded in uncached memory the size increase might
slow things down.
On QEMU Q35 postcar .text section size doubled, while heap section
has growen by 50%.
- zstd uses a lot of .bss (CTX is about 32KiB large). This might not be
available in some environments.
Orignal commit from 2022 was using zstd-1.5.2. Updated to zstd-1.5.7.
Change-Id: I34508268f8767008ef25cb9e466d201345881232
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/69753
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
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