import tariffs

[John Arbash Meinel]

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Martin Pool wrote:
> One way we can speed up Bazaar is to load less code at startup: this
> particularly helps on machines with magnetic disks and cold caches,
> but it's a good idea everywhere.  There are various things we can do
> including making things lazily loaded from registries and trimming
> unnecessary imports.  People have patched these in the past but it is
> easy for them to regress.
> 
> <https://code.edge.launchpad.net/~mbp/bzr/tariff/+merge/18970> adds a
> framework for checking what is loaded and some documentation;
> <https://code.edge.launchpad.net/~mbp/bzr/trim-imports/+merge/18971>
> is a small example of using it.
> 
> The next big step is probably to make more commands be lazily loaded.
> 

We also have to consider plugins, etc. I think getting the commands
setup refactored a bit would be good, and push us in the right direction.

But right now, some of the code that gets imported is because of:

1) Overriding an existing command in a plugin. Probably could be done
with a lazy registry.

2) Needing to register a Hook, which requires importing the module that
has the HookPoint. One option would be to move to a 'all HookPoints are
defined in module hookpoint.py'. At least, we ran into that for the
per-file merge hooks. We now always have to load 'merge.py' which is a
fairly involved module, and isn't needed for a lot of commands.

John
=:->

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