lioumens / cs310_heap_manager Goto Github PK

CS310: Operating Systems
Project 0: Heap Manager
Group Number: 18
Group Members: Michael Liou, Reyina Senatus, Steven Pierre
Time spent on project: ~20 hours total


Implementation Details:

********* Block Metadata: Headers **********

We use the default header provided in dmm.c for the project. Each header
contains size, *prev, and *next. Headers are added to both the free and allocated blocks. No footer is added. For allocated blocks,
space for *next and *prev pointers are still available for simplicity of
implementation. For more efficient results, allocated block header sizes can be
decreased.


************ Initialization: sbrk ***********

dmalloc is initialized once with 1kb of heap size. The beginning of the heap is
initialized to the start of the free list, and no additional heap size is
requested by sbrk.

************ dmalloc and dfree *************

dmalloc returns the pointer past the header part of the block. If there is no
more room on the heap, dmalloc will return NULL. dmalloc updates the static
variable freelist depending on which block becomes allocated. The freelist is
implemented as a linked list.

dfree takes a pointer argument pointing to the beginning of the allocated block,
just past the header. After freeing the block, the block is added back onto the
freelist and coalesce is called within dfree for every call to dfree. Note: coalesce does not defragment any
of the blocks to make additional room. coalesce method does not return anything
and takes no argument. coalesce only combines blocks when address spaces are
touching either at the end or beginning. Freelist updated for each coalesce call
if necessary.


********* Testing **********

basicdmmtest -- Our implementation will NOT pass this test with an initial slab
of 1kb. The initial heap size request must be increased. The requested dmalloc(940) will fail because we have initial dataspace
of 1000 bytes with a 24 byte initial header. After the first dmalloc(10) call,
this will allocate a block of 24 + 16 = 40 bytes, leaving 960 bytes. For the
dmalloc(940) call, we would need 24 + 944 = 968 > 960 bytes.

Tests were written during development to test the functionality of dmalloc, free,
coalesce independently. A general test was also created to test all
functionality together.

Final versions of all files are on master branch of compsci310-fall15-group18