NEXT_FIRST_BEST_WORST

• In First-Fit, the operating system searches through the list of free blocks of memory, starting from the beginning of the list, until it finds a block that is large enough to accommodate the memory request from the process.
• Advantages of First-Fit Allocation include its simplicity and efficiency, as the search for a suitable block of memory can be performed quickly and easily.
• First-Fit can also help to minimize memory fragmentation, as it tends to allocate memory in larger blocks.
• Disadvantages of First-Fit Allocation include poor performance in situations where the memory is highly fragmented, as the search for a suitable block of memory can become time-consuming and inefficient.
• First-Fit can also lead to poor memory utilization, as it may allocate larger blocks of memory than are actually needed by a process.
• These are Contiguous memory allocation techniques.
• In First-Fit Memory Allocation, the free/busy list of jobs is organized by memory location, low-ordered to high-ordered memory.
• The first job claims the first available memory with space more than or equal to its size.
• The operating system doesn’t search for appropriate partition but just allocates the job to the nearest memory partition available with sufficient size.
• In Best-Fit, the operating system searches through the list of free blocks of memory to find the block that is closest in size to the memory request from the process.
• Once a suitable block is found, the operating system splits the block into two parts: the portion that will be allocated to the process, and the remaining free block.
• Advantages of Best-Fit Allocation include improved memory utilization, as it allocates the smallest block of memory that is sufficient to accommodate the memory request from the process.
• Best-Fit can also help to reduce memory fragmentation, as it tends to allocate smaller blocks of memory that are less likely to become fragmented.
• Disadvantages of Best-Fit Allocation include increased computational overhead, as the search for the best-fit block of memory can be time-consuming and requires a more complex search algorithm.
• Best-Fit may also result in increased fragmentation, as it may leave smaller blocks of memory scattered throughout the memory space.
• Worst-Fit Memory Allocation is a process where the process traverses the whole memory and always searches for the largest hole/partition, then the process is placed in that hole/partition.
• The disadvantage of Worst-Fit Allocation is that it is a slow process because it has to traverse the entire memory to search the largest hole.
• The advantage of Worst-Fit Allocation is that it chooses the largest hole/partition, therefore there will be large internal fragmentation.
• The internal fragmentation in Worst-Fit Allocation will be quite big so that other small processes can also be placed in that leftover partition.
• Next fit is a modified version of ‘first fit’.
• Next fit begins as the first fit to find a free partition but when called next time it starts searching from where it left off, not from the beginning.
• This policy of next fit makes use of a roving pointer.
• The pointer in next fit moves along the memory chain to search for the next fit.
• This helps in avoiding the usage of memory always from the head (beginning) of the free blockchain.