For both fixed and dynamic memory allocation schemes, the operating system must keep list of each memory location noting which are free and which are busy. Then as new jobs come into the system, the free partitions must be allocated.
These partitions may be allocated by 4 ways:
1. First-Fit Memory Allocation 2. Best-Fit Memory Allocation 3. Worst-Fit Memory Allocation 4. Next-Fit Memory Allocation
These are Contiguous memory allocation techniques.
Best-Fit Memory Allocation:
This method keeps the free/busy list in order by size – smallest to largest. In this method, the operating system first searches the whole of the memory according to the size of the given job and allocates it to the closest-fitting free partition in the memory, making it able to use memory efficiently. Here the jobs are in the order from smallest job to largest job.
As illustrated in above figure, the operating system first search throughout the memory and allocates the job to the minimum possible memory partition, making the memory allocation efficient.
Advantages of Best-Fit Allocation :
Memory Efficient. The operating system allocates the job minimum possible space in the memory, making memory management very efficient. To save memory from getting wasted, it is the best method.
Disadvantages of Best-Fit Allocation :
It is a Slow Process. Checking the whole memory for each job makes the working of the operating system very slow. It takes a lot of time to complete the work.
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