Making diff fast (was Re: Some notes on distributed SCM)

[Robert Collins]

On Sun, 2005-04-10 at 18:47 -0400, Aaron Bentley wrote:
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> Daniel Phillips wrote:
> > On Sunday 10 April 2005 18:17, Aaron Bentley wrote:
> 
> >>This is what Arch does, and it's quite slow on large trees.  Robert
> >>Collins has recently improved this in Baz, but it doesn't change the
> >>fact that it's an O(versioned files) operation, rather than O(changed
> >>files).
> > 
> > 
> > But statting the full working copy kernel tree takes less than .1 second if 
> > the dentries are in cache, and it takes less than 5 seconds to get them in 
> > cache.  What is wrong with that?
> 
> 5 seconds isn't fast enough.  There's a huge psychological difference
> between 5-second and subsecond response times.  At 5 seconds, it's still
> an awkward delay.  If you just want a reminder of what you changed, it's
> annoying.
> 
> If we can find ways to make operations O(changed files), then we avoid
> penalizing people with large projects.
> 
> If subsecond is the common case, that's great.  Otherwise, I really do
> believe there's room for improvement.

I like the idea of O (changed files), but not at the cost of a good
interface. I find the 'lock this file for editing' interface really
unpleasant - it was one of the nice things about CVS & Arch that I
didn't need to do that.

Cheers,
Rob

-- 
GPG key available at: <http://www.robertcollins.net/keys.txt>.
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