[Bug 2038449] Re: Use pixz for compressing images

[Steve Langasek]

You say "We should pixz to parallelize the compression," but we are
passing -T4, which already parallelizes with xz.  And I believe we've
had previous discussions where the options were discussed, and a
conscious decision was made to use xz -T4 instead of pxz because the
implementation has to be in main as a runtime dependency of livecd-
rootfs (LP: #1701132); the same argument would apply to pixz (which
seems to be a completely different implementation from pxz for the same
purpose).

So why do you expect to see different performance from pixz than from xz
-T4?  Is -T4 the wrong number of threads, can we improve behavior using
-T0?

** Changed in: livecd-rootfs (Ubuntu)
       Status: New => Incomplete

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Title:
  Use pixz for compressing images

Status in livecd-rootfs package in Ubuntu:
  Incomplete

Bug description:
  We currently use xz for compression.

  live-build/ubuntu-cpc/hooks.d/base/disk1-img-xz.binary:14:    xz -T4 -c binary/boot/disk-uefi.ext4 > livecd.ubuntu-cpc.disk1.img.xz
  live-build/ubuntu-cpc/hooks.d/base/disk1-img-xz.binary:16:    xz -T4 -c binary/boot/disk.ext4 > livecd.ubuntu-cpc.disk1.img.xz

  At least on riscv64 this is a major driver for the build time. We
  should pixz to parallelize the compression.

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