Use pixz for compressing images

Bug #2038449 reported by Heinrich Schuchardt

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6
This bug affects 1 person
Affects Status Importance Assigned to Milestone
livecd-rootfs (Ubuntu)
Incomplete
Undecided
Unassigned

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.

tags: added: fr-5579
Revision history for this message
Steve Langasek (vorlon) wrote :

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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