MaverickCDBuildSpeed

Revision 3 as of 2010-05-18 14:07:59

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Summary

CD build speed has been creeping back up of late; attack it again.

Release Note

Not a user-visible feature, so no release note required.

Rationale

CD build times are a bottleneck in the release process. We have worked on this before, but we build many more images now and the problem has once again become acute. At the moment, live filesystem build times seem to be the worst offenders.

Design

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Implementation

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Code Changes

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

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

Lucid: big `apt-get install` phase in livecd-rootfs: 23min amd64, 9min i386

Total with tmpfs (Ubuntu): amd64 7min, i386 21min -> 16min

dpkg fsync->sync fix helps substantially (as elsewhere!)
 * will also investigate turning off syncing entirely

Cody says that concurrent builds helped them a lot

== Work items ==

 * Log total time for livefs builds [lamont]
 * rsync tree to a safe location following debootstrap, and following non-DVD builds; copy this back as the starting point when necessary, but only if the corresponding archive timestamp is correct [lamont]
  * Requires profiling to determine whether this is actually a win; Cody says this is a win in live-helper for at least the debootstrap stage
  * Union mounts may speed things up further - but probably not for maverick
 * Investigate effects on parallelisation of livefs builds [lamont]
  * (ISO builds are already parallelisable, but we generally don't since our bottlenecks are in livefs builds)
 * Investigate removing /usr/share/doc report and fdupes run from release builds [lamont]
 * Add and use dpkg option to turn off syncing entirely [cjwatson]

== Future (we can start investigating this any time) ==

 * Evaluate live-helper as a replacement for livecd-rootfs [cjwatson]
  * Would want to do file-by-file comparison of output and sign off on any differences


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