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DefragmentFreeSpace - Defragment all files and move them to the beginning of the filesystem

Description

When working in an emulator, emulator images can grow bigger than they have to be. With Oberon's tiny filesystems this is not a very big problem, but when sharing disk images with others, it can be helpful to remove unneccessary and potentially private information. Also when sharing disk images for my JavaScript emulator, it makes sense to defragment them first.

As the Kernel does not expose the last used sector of the filesystem, a small patch to Kernel.Mod is required (and a rebuild of the inner core) if you want to use the Defragmenter.

After defragmentation, the second step is to trim the filesystem at the last used sector. Therefore, the defragmenter writes an extra sector containing

!!TRIM!!---- … ---!!TRIM!!

after the last used sector. This sector is detected by my emulators to trim the image automatically; if yours does not, you can use the trim_defragmented_image.sh shell script instead.

There are two defragmenters available. The Lite version keeps a list of files in RAM, and can therefore only used if lots of RAM is available or there are only very few files. Also, opening and closing files will allocate buffer records and index records in Files.Mod; therefore even if the file list was stored on disk, garbage would accumulate until the GC runs next time (which only happens as a background task when the system is idle). To slightly reduce this problem, the Lite defragmenter can run in two phases: The first one Defragger.Prepare will copy file contents to the end of the disk, and the second pass Defragger.Defrag will nuke the filesystem and create a fresh one (In case the first pass is not called, the second pass will run the first one as well).

As this is no real option on systems with 1MB RAM and lots of files, there is another version of the Defragmenter available. It keeps a file list on disk (after the end of the filesystem), and uses a custom version of Files.Mod called DefragFiles.Mod, which can only open one file at a time, but does not need to do any allocations at runtime.

Installation

  • Apply DefragSupport.patch to Kernel.Mod.

  • Push the new modules.

  • Recompile Kernel.Mod and rebuild the whole system (including the compiler):

    ORP.Compile Kernel.Mod/s FileDir.Mod/s Files.Mod/s Modules.Mod/s ~
ORL.Link Modules ~
ORL.Load Modules.bin ~

ORP.Compile Input.Mod/s Display.Mod/s Viewers.Mod/s ~
ORP.Compile Fonts.Mod/s Texts.Mod/s ~
ORP.Compile Oberon.Mod/s ~
ORP.Compile MenuViewers.Mod/s ~
ORP.Compile TextFrames.Mod/s ~
ORP.Compile System.Mod/s ~
ORP.Compile Edit.Mod/s ~
ORP.Compile ORS.Mod/s ORB.Mod/s ~
ORP.Compile ORG.Mod/s ORP.Mod/s ~

  • Compile the new modules:

    ORP.Compile DefragFiles.Mod/s Defragger.Mod/s ~

    or

    ORP.Compile Defragger.Lite.Mod/s ~

  • Restart the system.

  • In case you are using the Lite version, run Defragger.Prepare and System.Collect.

  • Run Defragger.Defrag.