Memory allocation strategies, Data Structure & Algorithms

Q. Explain the various memory allocation strategies.                                                          

Ans.

Memory Allocation Strategies are given as follows

If it is not required to move blocks of allocated storage from one area of memory to the other area of memory,  it may be possible to relocate memory blocks that have been freed dynamically. Each time a request is made for storage or saving, the free area large enough to accommodate the size needed must be allocated. The most obvious methods for keeping track of the free blocks is to make use of linear linked list. Each free block contains a field comprising the size of the blocks and a field containing a pointer to be next free block. A global P for free block points to the 1st free block on this list. There are several methods or techniques of selecting the free block to use at when requesting storage.

The First - Fit Method:-       The free list is traversed sequentially or in order  to find the 1st free block whose size is greater than or equal to the amount requested. Once the block is found it is removed from the list (if it is greater than the amount requested). The 1st of these portions remains on the list and the 2nd is allocated.

The Best - Fit Method:- This method obtains the smallest free block whose size is greater than or equal to obtain such a block by traversing the full free list follows.
The Worst Fit method:- In this the system every time allocate a portion of the largest free block in memory. The philosophy at the back of this method is that by using small number of a very big block repeatedly to satisfy the majority of requested, many moderately sized blocks would be left un-fragmented.

The Free Storage List

 

The First fit method is as follows

294_memory allocation strategies.png

 

Best Fit method is as follows


 

1409_memory allocation strategies1.png

 Worst Fit Strategy is as follows

2008_memory allocation strategies2.png

Posted Date: 7/12/2012 8:56:27 AM | Location : United States







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