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Re: Delta combiner stress test results

From: <cmpilato_at_collab.net>
Date: 2002-07-25 23:44:42 CEST

Karl Fogel <kfogel@newton.ch.collab.net> writes:

> Branko ─Œibej <brane@xbc.nu> writes:
> > * After each set of tests, I recursively compared the working copies
> > (except the .svn directories). All the working copes were
> > identical, _except_ that the trunk svn/branch repo combination
> > corrupted files larget than 100k. I assume there's a latent bug in
> > the undeltification code on /trunk that shows up when trying to
> > undeltify files larger than the window size. We didn't notice it
> > because there are no such files in our repositories. The branch
> > sbuversion doesn't have this problem.
>
> Heh. Nice discovery.

I'm confused. Does large_file_integrity() in fs-test.c not do an
adequate job of testing?

> > Conclusion: The combiner is ready to be merged on the mainline. Please
> > test the code in /branches/issue-531-dev on your repositories, and let
> > me know the results. I'd be especially interested in results from
> > really huge repositores, e.g., the Linux kernel archives I know some
> > of you have created.
>
> I'd be *most* interested in results for repositories versioning huge
> files (~100MB), in two separate ways:
>
> - Huge file, but each revision is a small delta to it (like adding
> the string "fish" inside a giant image file)
>
> - Huge file, and each revision touches a lot of its bytes

In fact, large_file_integrity() does exactly this sort of thing. Here
are the in-line comments from the helper function:

  /* Create a big, ugly, pseudo-random-filled file and commit it. */

  /* Now, let's make some edits to the beginning of our file, and
     commit those. */

  /* Now, let's make some edits to the end of our file. */

  /* How about some edits to both the beginning and the end of the
     file? */

  /* Alright, now we're just going to go crazy. Let's make many more
     edits -- pseudo-random numbers and offsets of bytes changed to
     more pseudo-random values. */

> Our showstopper scalability issue had been that we didn't deltify
> files larger than the delta window size (~100k). Now that Brane's
> fixed that, wouldn't be interesting to see where our limits are? :-)

Ooh...perhaps these big files in large_file_integrity() weren't
actually being deltified... ?

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Received on Thu Jul 25 23:44:30 2002

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