10000 mkdumprd: replace lz4hc with lzma for better compression in squash image by licliu · Pull Request #87 · rhkdump/kdump-utils · GitHub
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mkdumprd: replace lz4hc with lzma for better compression in squash image #87

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Merged
merged 1 commit into from
Jun 4, 2025
Merged

mkdumprd: replace lz4hc with lzma for better compression in squash image #87

merged 1 commit into from
Jun 4, 2025

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licliu
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@licliu licliu commented May 27, 2025 •
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Among the compression algorithms currently enabled in RHEL-10, erofs+lzma has a higher compression ratio than lz4hc, this patch will replace it with lzma.

Testing shows when using erofs+lz4hc in RHEL-10, the size of the initramfs generated for local dump is 47M, and the size for nfs dump is 57M. After using lzma, the size is reduced to 39M and 45M. This is very closely compared to the 38M and 44M when using squashfs+zstd.

Summary by Sourcery

Replace LZ4HC with LZMA for EROFS compression in mkdumprd to reduce squash image sizes

Enhancements:

  • Switch EROFS compression algorithm from lz4hc to lzma in mkdumprd

Documentation:

  • Update script comments and usage text to reference lzma instead of lz4hc

@licliu
mkdumprd: replace lz4hc with lzma for better compression in squash image
41d733e 
Among the compression algorithms currently enabled in RHEL-10,
erofs+lzma has a higher compression ratio than lz4hc, this patch
will replace it with lzma.

Testing shows when using erofs+lz4hc in RHEL-10, the size of the
initramfs generated for local dump is 47M, and the size for nfs
dump is 57M. After using lzma, the size is reduced to 39M and 45M.
This is very closely compared to the 38M and 44M when using
squashfs+zstd.

Signed-off-by: Lichen Liu <lichliu@redhat.com>
@sourcery-ai Sourcery AI
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sourcery-ai bot commented May 27, 2025 •
edited
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Reviewer's Guide

This PR updates the mkdumprd script to switch the default squash image compression from lz4hc to lzma, updating the command invocations, option parsing, and help text accordingly to achieve better compression ratios on RHEL-10.

File-Level Changes

Change Details Files
Swapped default compression algorithm from lz4hc to lzma
  • Replaced ‘lz4hc’ flag with ‘lzma’ in compression command
  • Updated default compression variable to lzma
  • Modified option parsing to recognize lzma instead of lz4hc
 mkdumprd
Updated help and usage documentation for new compression option
  • Changed help text to reference lzma instead of lz4hc
  • Adjusted usage examples to show --compress=lzma
 mkdumprd
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Hey @licliu - I've reviewed your changes and they look great!

Here's what I looked at during the review
  • 🟢 General issues: all looks good
  • 🟢 Security: all looks good
  • 🟢 Testing: all looks good
  • 🟢 Complexity: all looks good
  • 🟢 Documentation: all looks good
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@hsiangkao
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hsiangkao commented May 27, 2025 •
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Hi @licliu, according to https://issues.redhat.com/browse/RHEL-36444, it seems erofs+lzma will be smaller than squashfs+zstd and I've applied -C65536 to dracut as in dracut-ng/dracut-ng#1296 (assuming that you already use the commit I submitted..)

So what's the difference here? In principle, lzma should have smaller image size than zstd.

@Barathrum-Liu
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Hi @hsiangkao, thanks for your attention!
Yes you are right, if we apply dracut-ng/dracut-ng#1296 it will be smaller image size than zstd. But currently that patch is not back-ported to RHEL-10.
I have created a ticket to dracut team for this patch.

@hsiangkao
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Hi @hsiangkao, thanks for your attention! Yes you are right, if we apply dracut-ng/dracut-ng#1296 it will be smaller image size than zstd. But currently that patch is not back-ported to RHEL-10. I have created a ticket to dracut team for this patch.

I do think the kdump use case doesn't need -C4096 as Android, so -C65536 will be useful for you to get even smaller images.

@coiby coiby merged commit 1d40ea3 into rhkdump:main Jun 4, 2025
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@coiby coiby coiby approved these changes

@hsiangkao hsiangkao hsiangkao approved these changes

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@licliu @hsiangkao @Barathrum-Liu @coiby
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