Public bug reported:
Changing the default compression method of initramfs to zstd using
hardcoded compression flag "-19 -T0" takes 200MB memory in return for
40MB reduction of disk IO. I think it is too much memory usage for some
fraction of seconds while booting.
The default compression method of initramfs was changed in Bug #1931725 for
impish but the runtime memory usage was not discussed well.
the test results by modifying compression command in /usr/sbin/mkinitramfs on a
small VM (amd64, 512MB RAM, 1vCPU, with 5.13.0-16-generic image)
| RSSmax | initrd size
zstd -q -19 -T0 | 214MB | 64MB (+-0MB)
zstd -q -3 -T1 | 44MB | 84MB (+20MB)
lz4 -9 -l | 15MB | 107MB (+43MB)
Since the hardcoded flag uses "-T0", more memory will be used if more CPU
threads are available.
Please reconsider the default compression method or patch the hardcoded flag to
"-3 -T1" (=zstd default).
** Affects: initramfs-tools (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1944082
Title:
initramfs-tools: zstd uses too much memory in mkinitramfs
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