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Comment by andrewstuart | Hacker News Reader

This is 20x faster build time to create the initramfs image, is that correct?

It's not 20x faster to boot?

Yes, 20x faster build of initramfs image. But boot is also a bit faster due to the faster go-based initial init process, I'd guess:

> Measuring early boot time using qemu, I measured the dracut-generated initramfs taking 588ms to display the full disk encryption passphrase prompt, whereas minitrd took only 195ms.

Is that an interesting difference, though? At least on my machine, boot time is dominated by... grub loading the kernel and initramfs. Which is actually ridiculous when you consider it's a few dozen megabytes on a NVMe. I have't inveatigated what's up yet.

On a VM, where you don't have to deal with the incredible slowness of pre-boot hardware, that's a big speedup.

On a physical computer where you have to wait 15 seconds for the machine to post anyway, yeah it's not a big difference.

BIOS I/O calls are extremely slow. EFI boot-time services are significantly faster.

That's on a machine with EFI.

fyi a quick way to see this is with systemd-analyze

  systemd-analyze plot > bootplot.svg

  systemd-analyze critical-chain

  systemd-analyze blame

Systemd-analyze doesn't know about grub.

Certainly is to me! I build embedded Linux devices. Our current boottime from cold-boot to fully functioning is roughly 3 seconds. I would really like to get it lower and shaving off almost half a second would be amazing.

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