[Bug 1627190] Re: livecd-rootfs: .pyc files stripped from desktop ISO livefs, makes python startup slower

[Iain Lane]

Please review the merge proposal.

Draft email to -release.

---
Dear flavours,

For a long time, we've been stripping .pyc files from live images in
order to save space. This is a speed-vs-space tradeoff, as in the
absence of .pyc files, applications need to either perform the byte
compilation on first startup or suffer a speed penalty.

Towards the end of the 16.10 cycle, we reviewed our position to see if
it still made sense in an era where most of our images are less space
constrained. On an Ubuntu Desktop live CD, the saving is approximately
19 MB. Unfortunately I don't have good numbers for the speed gain, but
it is noticable. We consider this an acceptable cost for faster app
startup, and so for Zesty we will invert this default and make .pyc
stripping opt-in instead of opt-out.

This is an announcement to make flavours aware. If you wish to opt back
in, please reply to this email or raise a merge proposal against livecd-
rootfs.

Cheers,
---

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https://bugs.launchpad.net/bugs/1627190

Title:
  livecd-rootfs: .pyc files stripped from desktop ISO livefs, makes
  python startup slower

Status in livecd-rootfs package in Ubuntu:
  New

Bug description:
  It seems we've had code in livecd-rootfs for roughly forever to strip
  .pyc files out of the squashfs included on desktop images.  There is
  an override to skip this for server and cloud images, but we
  discovered this recently because the missing .pyc files on ubuntu-core
  images causes very long start-up times for python apps on some armhf
  systems.

  So the question is, is this still a sensible optimization on Ubuntu
  Desktop images?  It was done at a time when space was tight; that's
  much less of a concern now than it was.

  If this does still make sense for Desktop, we should probably at least
  invert the logic to make this opt-in rather than opt-out so that new
  image types on ARM don't get caught out with the problem.

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