Re: Hideously slow VC status queries fixed

[Alexandru Harsanyi]

On 27 Dec 2007, at 11:41 AM, Dan Nicolaescu wrote:

> "Eric S. Raymond" <address@hidden> writes:
>
> > It gives me great pleasure to be able to announce that I have found,
> > and fixed, the bug that made C-x v d so godawful much slower than the
> > underlying commands.
>
> Thank you so much for doing this!
>
> There's still one source of inefficiency: files that are not vc- 
> registered
> at all. For example object files in a build tree.
>
> Try this:
>
> cd emacs/lisp/term   (because it is a small subdir)
>
> for FF in `seq 1 1000`; do touch obj${FF}.o; done
>
> (just create 1000 .o files)
>
> emacs -q
> M-x elp-instrument-package RET vc RET
> C-x v d emacs/lisp/term RET
> M-x elp-results RET
>
> That will show  1000 calls to vc-bzr-registered, vc-git-registered,
> vc-arch-registered, vc-svn-registered etc etc.

One way to reduce the number of calls is to use the `vc-BACKEND- 
responsible-p' functions to determine which backends are responsible  
for files in a directory.  It will than only call the `vc-BACKEND- 
registered' function for the responsible backends only.

The speed of the vc-BACKEND-registered call be improved by having the  
`vc-BACKEND-dir-state' function set a property meaning 'not- 
registered' for every file that is not registered with that BACKEND.   
vc-BACKEND-registered will than check for that property before  
invoking the BACKEND command.

Best Regards,
Alex.