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SnapshotCM Newsletter for March, 2012


  • Editor's Blog
    • New Release
    • Subversion Import
  • Trends: CPU Performance and Implications for Version Control
  • Recommended Releases
  • Links We Like

Editor's Blog

New Release

We've had an accumulation of changes, two of which we wanted to get out quickly, and which are now posted in the 1.85.5 release. The first change is an important fix to the resolve-to-target resolution when copying changes between snapshots. If your source revision is derived from the target revision and not on a branch, then the source is copied to the target rather than the target revision being kept. This defect is in the client, not the server, so all users should update to avoid this occurring.

The second change improves the robustness of the server. We recently had a customer whose server would become unresponsive. After restarting, it would run for a while, then again become unresponsive. Eventually, we discovered that someone was running many parallel wls commands on many snapshots to see if anything had changed. The 100+ commands starting in an instant were overloading the server and putting it into a state where it thrashed without doing much real work. The result was that normal user activity became impossible. Of course they stopped running the overloading commands, but we also wanted to better handle this situation in the server. The new release does that by queuing the excess requests until they can be handled efficiently. With the change, the server throughput remains high under heavy load, and hundreds of parallel commands can complete efficiently.

New Feature

A third change is that the Compare Browser now shows a check in comment summary for each file. I've already greatly appreciated how this helps quickly understand what changes I am copying. Which points out how even "little" features can have a big impact. By improving understanding of actions being taken, users are more confident, make fewer mistakes and ultimately are more productive. And that is always our goal.

For a complete list of user-visible changes, see the Change List.

Subversion Import

In the past month, we've also added the ability to import revision history from subversion. All revisions, comments, change dates and SVN states are imported, with the SVN states mapped to release snapshots with sequential relationships. Branches and file merges are also correctly imported. If you have an SVN repository to import, let me know. We are looking for more repositories to test on.

As always, we welcome your feedback and ideas.

Scott Kramer

Trends: CPU Performance

In past columns, we looked at how the changes in disk capacity, disk performance and network performance affect version control. Now we examine CPU performance trends and implications.

Faster, More

The mantra of faster, smaller, cheaper hardware, true for so many years, doesn't hold so universally any more. Yes, hardware is faster, but with a caveat: the speed is only available to applications designed to use the multiple cores of the newer hardware. Single threaded application still benefit from moving up to 64-bits, as well as from faster memory subsystems, smarter CPU implementations, better and larger caches, but dramatic performance gains require applications to use multi-threading. In short, the free increases in performance experienced by all software applications in the past are unlikely to continue without some changes to the application software itself.

Benefits Today

Many applications are fast enough to seemingly have little need to parallelize or adopt other changes necessary to make full use of the newest systems. Yet, inevitably the creative among us will identify uses for all those spare CPU cycles. Here are a few uses that come to mind for version control:

  • background compression of files stored in a version control repository,
  • compression of network traffic to improve effective client-server throughput,
  • multi-threading to better handle greater numbers of users and requests,
  • improved responsiveness in the GUI driven by real-time external events (such as file system changes), and
  • managing workspace file state based on file content check sums rather than date-time modified.

Some of these improve user experience, while others save space or time—which also improves user experience. All of these techniques are in use today in SnapshotCM, and provide a more robust user experience with no negative down-side—possible because of the excess CPU performance available.

Benefits Tomorrow

What else could we do in version control because of the additional CPU power available? What new paradigms might be enabled? Send me your thoughts...

Do you see other fundamental technological changes affecting past version control assumptions? I welcome your thoughts.

Recommended Releases

The following releases are recommended:

  • - The newest features and fixes.
  • 1.84.2 / - A known stable release.
  • 1.82.06 / 1.82.07 / 1.82.08 - stable version with the old (single mount) workspace model.

If you are running any other release, we recommend that you update to the latest recommended version that your license allows.

For a complete list of user-visible changes, see the Change List.

Links We Like

Links we find interesting, fun, or occasionally useful.

Have an interesting link to share? Please send it to

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