[MERGE] log|less 590% to 727% faster

[John Arbash Meinel]

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Aaron Bentley wrote:
> John Arbash Meinel wrote:
> 
>>> I like it. It is nice and simple, and the whole point is wanting to get
>>> the first screenfull up as soon as possible.
>>>
>>> Did you ever look into creating a long-live (1000+ revs) branch with
>>> actual changes?
> 
> No, I haven't looked at that.  Thanks for the reminder.  log FILENAME
> and log -v haven't really been at the top of my mind.  Worth looking at.
> 
> I think I'm happy with 44 milliseconds for the first screenfull.  Merges
> shouldn't affect that very much.  Now if only we can pull down that
> startup time...
> 
> Aaron

Not really before we change our dirstate format, so that we don't have
to load cElementTree.

Either that, or we hack up ElementTree and copy, and pre-install them.

Actually, we could just mess with the import of 'inspect' for 'copy'.

I just played with something, and I found a way that 'demandload()' can
actually hack-into sys.modules so that other modules actually load a
demandload version.

This semi-evil hack is available from here:
http://bzr.arbash-meinel.com/misc/demandload_through_sys/

Basically, you can do:

demandload(globals(), 'inspect foo bar')
sys.modules['inspect'] = inspect
sys.modules['foo'] = foo
sys.modules['bar'] = bar

And then anyone else who tries to do 'import foo' actually gets the
demandload object until they access an attribute.

If you look at my demandload branch of bzr, I played with it, and I now
have the time for 'bzr --no-plugins root' down to 240 ms
These are the overall timings:

		rocks	root
original	493	504
demandload	148	281

And that is even without '--no-aliases' now that we aren't loading
validate.py. (It still takes 35ms to load configobj, but that is down
from 135ms).

So now that I've played with it some, we might actually want to
considered adding demandload into the core.
I realize it is a little evil to do my monkeypatching demandload, but it
can shave off as much as 100ms from the startup time. Which can be 1/2
the time we spend.

John
=:->
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