Accelerate build_tree by using working tree files

Aaron Bentley aaron.bentley at utoronto.ca
Wed Dec 19 15:16:49 GMT 2007


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Ian Clatworthy wrote:
> Aaron Bentley wrote:
> Together with the hard link patch, the results are pretty nice IMO:
> 
> * creating a local branch: 63.9 -> 33.1

Could you send me the callgrind.out for that?  I would have expected
better.  This is still using a shared-repo, right?  It's barely reading
or writing any files, so what's it doing?

> * disk usage drops a lot as well: 1.53G to 1.21G

The additional usage of a hardlinked branch in a shared repo should be
close to zero.  Branches are extremely cheap, as are hard links.  The
dirstate file is probably the biggest file that would be *created*.

> The disk usage is the total of a repo + 2 branches + checkout + a
> lightweight checkout, i.e. mostly 4 working trees.
> 
> Note that checkout and lightweight checkout performance drop slightly
> though: 64 -> 66 seconds.

Are you using --files-from?  (You're not branching or checking out
*from* a lightweight checkout, are you?  That case wasn't handled by
that version.)

> I benchmarked with both so I don't have figures without this yet. It's
> great for the space efficiency gain regardless isn't it?

It is valuable for that alone.  But I don't expect to turn hardlinking
on by default.  So it would be useful to know how much of an additional
gain it is.

Aaron
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