ymalloc

Yet another implementation of malloc and free

Heap visualization of glibc malloc (left) vs ymalloc (right) after many iterations

mapper.rb visualization by Jacob Sorber on youtube

Implementation Details

Some notable details about the internal representation

• Allocated memory comes from the data segment using sbrk
• An implicit list of blocks is maintained by storing block sizes in (8 byte) headers and footers immediately before and after each allocation
• An explicit free list is maintained by doubly linked pointers in freed blocks
  • The minimum allocation therefore must be at least the size of two pointers (16 bytes)
• Adjacent freed blocks are coalesced and appended to the free list

Improvements

• Use mmap instead of sbrk
• Slightly more space can be used to store a checksum of block sizes and pointers in order to detect block corruption