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Re: The small commit problem

From: <kfogel_at_collab.net>
Date: 2003-07-29 21:38:01 CEST

Philip Martin <philip@codematters.co.uk> writes:
> I have been looking at a cvs2svn conversion and wondering why the
> Subversion repository is so much larger than the CVS one. One of the
> things that occurred to me is that the creation of a directory node in
> the Subversion filesystem might make small commits relatively
> expensive, particularly if the directory has a large number of
> elements.
>
> I have been experimenting with scripts like the one at the end of this
> mail. It creates a simple repository containing a number of files and
> then makes lots of "small" changes to measure how the repository
> grows. I have tried both renaming a file (one rename per commit) and
> editing a file (append a few bytes to one file per commit).

"Thank goodness for Philip."

There, now that that's out of the way:

> Thus a Subversion repository doesn't handle "small" commits
> particularly well, there is a sort of threshold on the minimum size
> for each commit. This could explain why we are getting reports that
> CVS repositories convert to much larger Subversion repositories.
>
> Does that sound plausible? If it does I wonder what we could do to
> change it: make the nodes less expensive, or use some sort of "diffy"
> directory storage, or...

Yes, I think it might be time to turn on directory deltification. It
was turned off here, I think:

   ------------------------------------------------------------------------
   rev 1043: cmpilato | 2002-01-24 10:03:50 (Thu, 24 Jan 2002) | 12 lines
   
   Turning off deltification of directory entries lists (should this be
   wrapped in #ifdef SVN_FS_DELTIFY_DIR_ENTRIES and made into a
   compile-time feature?)
   
   * subversion/libsvn_fs/deltify.c
   
     (deltify): Added 'props_only' argument.
   
     (svn_fs__stable_node): Pass 1 for 'props_only' argument to deltify()
     if node we are stabilizing is a directory.

But undeltification performance is greatly improved since then...

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Received on Fri Aug 22 09:20:56 2003

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