Memory Partitioning

Buddy System

The buddy system is based on dividing the memory into fixed-size blocks, and whenever a process requests memory, the system finds the smallest available block that can accommodate the requested memory size.

  • Entire space available is treated as a single block of
  • If a request of size such that then the entire block will be allocated
    • Otherwise the block is split into two equal sized buddies
    • Process continues until smallest block greater than or equal to is generated

It's not that complicated

Split memory into 2, until splitting more would not fit.


void get_hole(int i) {
    if (i == (U + 1)) <failure>;
    if (<i_list empty>) {
    get_hole(i + 1);
    <split hole into buddies>;
    <put buddies on i_list>;
    <take first hole on i_list>;


We can represent this as a tree: