GATE CS 2015 Set 2 Q30 — Memory Management and Virtual Memory

The Best-Fit memory allocation policy assigns a process to the smallest available memory partition that is large enough to accommodate it. This minimizes the leftover wasted space (internal fragmentation) in the allocated partition.

Let the initial set of available partition sizes be:

$$\{200\text{ KB}, 400\text{ KB}, 600\text{ KB}, 500\text{ KB}, 300\text{ KB}, 250\text{ KB}\}$$

We allocate the processes of sizes $357\text{ KB}$, $210\text{ KB}$, $468\text{ KB}$, and $491\text{ KB}$ sequentially:

1. Process 1 ($357\text{ KB}$):
   • Partitions large enough: $400\text{ KB}$, $500\text{ KB}$, $600\text{ KB}$.
   • The smallest among these is $400\text{ KB}$.
   • Allocation: $400\text{ KB}$ partition is allocated.
2. Process 2 ($210\text{ KB}$):
   • Partitions large enough: $250\text{ KB}$, $300\text{ KB}$, $500\text{ KB}$, $600\text{ KB}$.
   • The smallest among these is $250\text{ KB}$.
   • Allocation: $250\text{ KB}$ partition is allocated.
3. Process 3 ($468\text{ KB}$):
   • Partitions large enough: $500\text{ KB}$, $600\text{ KB}$.
   • The smallest among these is $500\text{ KB}$.
   • Allocation: $500\text{ KB}$ partition is allocated.
4. Process 4 ($491\text{ KB}$):
   • Partitions large enough: $600\text{ KB}$.
   • Allocation: $600\text{ KB}$ partition is allocated.

After allocating all four processes, the partitions that remain unallocated are:

$$\mathbf{200\text{ KB}} \quad \text{and} \quad \mathbf{300\text{ KB}}$$

Thus, the correct option is A.