Hi,
I am a big fan of ZSTD - here version 1.5.6 on Debian/unstable AMD64.
When playing with CONFIG_MODULE_COMPRESS_ZSTD=y I observed a 35MiB
greater linux-image Debian file.
Debian: ~100MiB <--- CONFIG_MODULE_COMPRESS_XZ=y
Selfmade: ~135MiB <--- CONFIG_MODULE_COMPRESS_ZSTD=y
So, I checked the used compression-level of ZSTD in the build-process:
[ vmlinux.bin.zst ]
$ grep zstd build-log_6.10.1-1-amd64-clang18-kcfi.txt | grep vmlinux.bin.zst
{ cat arch/x86/boot/compressed/vmlinux.bin
arch/x86/boot/compressed/vmlinux.relocs | zstd -22 --ultra; printf
\370\040\157\003; } > arch/x86/boot/compressed/vmlinux.
bin.zst
[ amdgpu.ko.zst ]
$ grep zstd build-log_6.10.1-1-amd64-clang18-kcfi.txt | grep '\-T0' |
grep amdgpu
zstd -T0 --rm -f -q
debian/linux-image-6.10.1-1-amd64-clang18-kcfi/lib/modules/6.10.1-1-amd64-clang18-kcfi/kernel/drivers/gpu/drm/amd/amdgpu/amdgpu.ko
Here some numbers:
[ Values in KiB ]
$ du -k amdgpu.ko*
29264 amdgpu.ko
5672 amdgpu.ko.zst <--- XXX: -T0
4264 amdgpu.ko.zst_T0-19 <--- XXX: -T0 -19
4260 amdgpu.ko.zst_T0-22
4308 amdgpu.ko.zst_T0-22-ultra
$ time zstd -T0 -v amdgpu.ko
*** Zstandard CLI (64-bit) v1.5.6, by Yann Collet ***
Note: 2 physical core(s) detected
zstd: amdgpu.ko.zst already exists; overwrite (y/n) ? y
amdgpu.ko : 19.38% ( 28.6 MiB => 5.54 MiB, amdgpu.ko.zst)
real 0m2,496s
user 0m0,448s
sys 0m0,064s
$ time zstd -T0 -19 -v amdgpu.ko
*** Zstandard CLI (64-bit) v1.5.6, by Yann Collet ***
Note: 2 physical core(s) detected
amdgpu.ko : 14.56% ( 28.6 MiB => 4.16 MiB, amdgpu.ko.zst)
real 0m22,821s
user 0m22,759s
sys 0m0,080s
My wish is to use the zstd-option "-T0" (see vmlinux.bin.zst) everywhere.
For CONFIG_MODULE_COMPRESS_ZSTD=y: Add compress-level = -19
NOTE: -22 w/ or w/o ultra has no big effect here and increases even
more build-time.
What do you think?
Thanks.
Best regards,
-Sedat-
