Slow load from CD or DVD

  • All,

    I have created a simple dialog application that needs to be run from a CD or DVD. The application is written using Qt 4.7.4 and is running on Windows 7. If I launch the application from the HDD it loads immediately, but if I launch it from a CD or DVD it seems to take a very long time, on the order of 10-15 seconds to display the UI.

    I thought maybe reading settings from an INI file using QSettings in the contructor of my dialog was taking too long, but I moved the loading of the settings into a seperate thread and it didn't have any affect.

    My dialog only has 3 check boxs and two push buttons, so it really is not much to load.

    Anyone run into performance problems when running an application from Disc as opposed to from HDD or memory stick?


  • Moderators

    Do you load Qt dynamically? I would suspect it takes the OS a lot of time to load QtCore and - especially - QtGui. 2 things that might help here are:

    • make sure to deploy Qt release dlls (they are much, much smaller in size)
    • try to make them reside close to the application, so that CD/DVD head does not need to jump around too much

    Alternatively, you can compile statically just to be sure.

  • Well, The DVD/CD is much much much slower in operation then a HDD! It always is. So when having a complete program on a CD is will be hard to load into memory before execution. As sierdzio says is very much so. Make the program as small as possible by using the dynamic linked methode and copy the used dll's into the program dir on the CD. That might do the trick.

  • All the DLLs are in the same directory as the program, and the program is only 81KB so it is pretty small already. I am going to try the static compile option.

  • I built Qt statically, and statically linked my app against it, and it didn't seem to make much difference.

  • something is not right here. An 81 KiB file on CD should be loaded into memory nearly instantly. Even the ~12 MiB of the Qt so's should be in memory in no time.

    Is it a modern CD drive (52x or something like that?), does other data of that magnitude copy fast to your HDD?

  • Yes this has been run on a few different machines. All either i5 or i7 machines with modern DVD and Blu-Ray drives.

  • Another strange behavior that is being is seen is the first time run from the DVD or CD there is a crash when you exit the application, but if you launch the application again,leaving the disc in and exit there is no crash.

  • the crash was unrelated to this slowdown. I have resolved the crash.

  • do you have resolved the problem?

  • i have the same problem, can you help me?

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