Oct04

A memory management system is working with a total memory size of 700K and uses contiguous allocation and variable sized partitions so that no internal fragmentation occurs. It currently has three free blocks available. Their sizes are 50K, 155K, and 100K, respectively, and their location in the memory is as below. The order of the free list is just the increasing order of the beginning addresses of the free blocks.

0      --- increasing addresses -->          700K
+-------+-----+------+------+------+------+------+
| used  | 50K | used | 155K | used | 100K | used |
+-------+-----+------+------+------+------+------+

Show how First-Fit would allocate memory to 3 new processes of size 90K, 100K, and 60K (in that order).
Show how Best-Fit would allocate memory for the same three processes.

Request	First-Fit	Best-Fit
	50,155,100	50,155,100
90	50,65,100	50,155,10
100	50,65	50,55,10
60	50, 5	wait

At the third request (for 60K), both First Fit and Best Fit has a free list with a total size of 115K, more that enough. However, for Best Fit this 115K is broken (fragmented) into three pieces of size 50K, 55K, and 10K. None of these 3 blocks is big enough for the request. So the request must wait until some process terminates and releases more memory.

Example