bzr performance (blitz speed on GNU/Linux compared to M$)

[John Arbash Meinel]

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>>
>> Also, things slow down at some really weird times. When we are building
>> a working tree, we stage it in a limbo area. And add entries to that as
>> we go. When we have finished, for most entries we rename their
>> containing directory into the final location in the workingtree. I've
>> seen it where the "creating new file" portion goes fast, but doing "mv
>> ..bzr/checkout/limbo/dir working-dir" my system actually seems to just
>> hang for about 5-10s not doing anything (that I can see).
> 
> Don't forget: for mv on windows there is fancy_rename trick is used:
> old file renamed to temp name, new file renamed to old name and then
> old file with temp name is deleted. Actually 3 IO operations instead of 1
> atomic on Linux.
> 

That is true in some circumstances, but for building a working tree, we
just use "os.rename" unless it conflicts, when we fallback to something
else.

So this particular work does only do 1 I/O rather than 3.

John
=:->
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