PartitionerOptimisation

Revision 2 as of 2009-11-25 16:38:28

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Summary

ubiquity's partitioner is kind of slow, especially with lots of disks/partitions. This is partly due to slowness in the underlying partitioner that's also visible in d-i (though less annoying there) and partly due to inefficiencies in the ubiquity integration. Let's make it be more pleasant to use.

(Note that this is mainly about the manual partitioner, although some effects would likely ripple out to the automatic partitioner as well.)

Release Note

This section should include a paragraph describing the end-user impact of this change. It is meant to be included in the release notes of the first release in which it is implemented. (Not all of these will actually be included in the release notes, at the release manager's discretion; but writing them is a useful exercise.)

It is mandatory.

Rationale

This has been an ever-increasing source of user complaints, and it would be lovely to spend some time optimising it. We just need to make sure that the time spent doing so isn't open-ended, of course.

User stories

Assumptions

Design

You can have subsections that better describe specific parts of the issue.

Implementation

This section should describe a plan of action (the "how") to implement the changes discussed. Could include subsections like:

UI Changes

Should cover changes required to the UI, or specific UI that is required to implement this

Code Changes

Code changes should include an overview of what needs to change, and in some cases even the specific details.

Migration

Include:

  • data migration, if any
  • redirects from old URLs to new ones, if any
  • how users will be pointed to the new way of doing things, if necessary.

Test/Demo Plan

It's important that we are able to test new features, and demonstrate them to users. Use this section to describe a short plan that anybody can follow that demonstrates the feature is working. This can then be used during testing, and to show off after release. Please add an entry to http://testcases.qa.ubuntu.com/Coverage/NewFeatures for tracking test coverage.

This need not be added or completed until the specification is nearing beta.

Unresolved issues

This should highlight any issues that should be addressed in further specifications, and not problems with the specification itself; since any specification with problems cannot be approved.

BoF agenda and discussion

"Scanning disks"
Equivalent to pressing Enter on each partition and going back, in d-i
This clearly involves redisplaying the partition tree at each step, so may be able to cache that part

bootchart for shell profiling?
focus on 'choices' scripts in /lib/partman/; slowness here will be noticeable on generating menus in partman

cdebconf:
 * last time Colin tried, didn't make a significant speed difference; should recheck this
 * doesn't support 'seen' flag, so be careful about semantics (particularly around language/timezone/keymap)

Use bootchart for all of d-i, or all of the live CD.
Bootchart times out; will need magic runes to keep it running.

Use python bindings to libparted?

We're calling ntfsresize multiple times.

Unrelated, but worth noting:
 * Use a status bar rather than a pop-up progress window.

Partition bar construction in cairo is fairly slow (evand)
 * repeated calls out to `os-prober`, which is slow

Big pause after partitioner while a check script runs du
 * Find out the size of /rofs when ubiquity starts, and plug that into the sufficient free space check and the total_size variable in scripts/install.py
 * if df is reporting incorrect sizes, it should be fixed and ubiquity should use that for determining sizes.

Goal: 20% of current time for two disks with eight partitions each (*handwave*)

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