Implementation of malloc(), free(), realloc(), calloc() in C.

There are three versions of the memory allocator. The mm-naive.c is the naive implementation of the memory allocator. It just uses the virtual memory as a large array of bytes to allocate memory and never frees memory. This approach achieves a high throughput (number of requests per time) at the expense of memory utilization. The second implementation mm-implicit.c uses an implicit list to store both allocated and free blocks. This version can reuse allocated blocks, thus achieving better memory utilization. However, since we keep a long list of allocated and free blocks, the running time of malloc() will be much longer. The third implementation mm-explicit.c balances throughput and memory utilization. It uses an explicit free list to store only free blocks since we don't care about allocated blocks. Memory utilization of mm-implicit.c and mm-explicit.c is roughly the same, but the explicit free list version has better throughput.

These implementations of malloc also impose a minimum block size of 4 words for each allocated block (header, footer, payload, and padding). With the free block in the explicit free list version, we can use the payload to store the predecessor and successor free blocks in the explicit free list.

Implement the memory allocator using a segregated free list. This is a more sophisticated version of the explicit free list one since it will keep track of many explicit free lists with different size classes. This design of the dynamic memory allocator achieves both high throughput and memory utilization.