Launchpad Entry: lpia-versus-i386
Is the lpia architecture a necessary pain or is i386 good enough? How many lpia specific changes do we still carry? Can we provide a tool to upgrade existing lpia installs to i386 (or i386 to amd64 or arm to armel...)? What can we do with the lpia architecture right now?
Probably not release notes worthy in the current state.
The lpia architecture is a maintenance burden for Ubuntu; we need to make sure it's useful enough or dropped: either by asserting that it is useful enough, or by changing it into something more useful. The lpia architecture also creates problems of its own (incompatibility with third party .debs).
Review of the lpia architecture
- Little perceived performance gain
- Some delta with Debian
- Incompatibility with third party i386-only .debs
- Not a clear use case
Changes which might warrant keeping lpia
- Additional changes to the toolchain to improve performance for upcoming new
- CPU generation
- Expected future architecture changes that may benefit from optimisation
- Incompatible future architectures: actually wont happen anytime soon as
- Moorestown will be binary compatible
Compiler flags considerations
On some the Moblin list, an Intel person suggested to use:
- -O3: does not show significant improvement in testing: modprobe is counter-example with -Os
- SSE: several applications are expected to benefit
- -static: performance improvements do not justify additional maintenance efforts
- -march=nocona: implies OOE which Atom is documented not to support - unlikely to be adopted
However the correct flags to use as explained by Rusty Lynch (Moblin) are:
[ citation needed! ]
Arch conversion tools
- Tools would generally need lots of love, and aren't ready yet, but there are some good use cases.
- archtakeover / debtakeover
arm -> armel, but could be repurposed
- Not complete in Debian, fragile
Consider for i386 -> amd64
- Leverage ubiquity-preserve-home for cross-arch applications
- Keep the lpia architecture in maintenance mode. Discuss the use of the best compiler flags for lpia with the Ubuntu Foundations Team.