[merge] use os._exit

[John Arbash Meinel]

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John Arbash Meinel wrote:
> Martin Pool wrote:
>>> This changes bzr to exit through os._exit when it's done.  This function
>>> differs from sys.exit in that it does not finalize or gc any objects
>>> that still exist.  That has two benefits:
>>>
>>> It suppresses the intermittent failure of the smartserver 
>>> tests that I wrote about yesterday -- python never goes into
>>> the terrible state of modules disappearing while in use
>>>
>>> By avoiding gc of things that are about to be destroyed we save some
>>> time at shutdown -- about 50ms in my test, or 14% of the time to do bzr
>>> status in a bzr tree.
> 
> I like the performance improvements, but avoiding finalization and gc
> seems a little unclean.


After looking closer, I'm probably +0, since this is occuring only in
the main 'bzr' script, and not in any of the bzrlib code.

I did try the gc.disable() trick that was mentioned in IRC, and it
dropped the 'bzr rocks' time down to 148ms, so between os._exit() and
gc.disable() we spend 50ms in 'bzr rocks' just doing cleanup.

John
=:->
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