Assignment: Heap Memory

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Heap Memory

This assignment is a Xinu assignment allowing the student to more firmly understanding of how an operating system works. This assignment is part of the Student Built Xinu track for professors that are Teaching With Xinu. The entire working directory containing your Xinu operating system will be submission for this assignment.


First, make a fresh copy of your work thus far.

  cp -R <old Xinu directory> <new Xinu directory>

Untar the new project files on top of this new directory:

  tar xvzf <tar-ball location>

You should now see the new project files in with your old files. Be certain to make clean before compiling for the first time.

Getmem and Freemem

The files include/memory.h and system/initialize.c define and initialize a free list of available memory blocks on the heap. Implement system/getmem.c and system/freemem.c to dole out blocks of requested memory and properly maintain the free list. Use First Fit with simple compaction. (Compaction is the "stretch" problem in this assignment -- get everything else working first.)

Delete the file system/getstk.c and replace the lone call to this function in system/create.c with a proper call to getmem() instead. Modify system/kill.c to call freemem() to deallocate a process stack when a process dies.


Project credit will be divvied up evenly between getting memory, freeing memory, and compaction. By now, you should be aware that rigorous testing is the key to success in these projects. Our test cases will include at least:

  • Verifying that your getmem() and freemem() functions operate correctly over a variety of request sizes
  • Checking your memory free list under a wide variety of conditions; if you are not writing a helper function to print out your free list, you are probably not serious about understanding what your system is doing
  • Allocating and freeing as much memory as possible, (How can you tell whether you have a memory leak?)
  • Verifying that your freemem() compaction works.