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Unformatted text preview: ce there is no coalescing, allocated blocks do not need an allocated/free ﬂag in the header. Thus allocated blocks require no headers, and since there is no coalescing, they do not require any footers either. Since allocate and free operations insert and delete blocks at the beginning of the free list, the list need only be singly-linked instead of doubly-linked. The bottom line is that the only required ﬁeld in any block is a one-word succ pointer in each free block, and thus the minimum block size is only one word. A signiﬁcant disadvantage is that simple segregated storage is susceptible to internal and external fragmentation. Internal fragmentation is possible because free blocks are never split. Worse, certain reference patterns can cause extreme external fragmentation because free blocks are never coalesced (Problem 10.10). Researchers have proposed a crude form of coalescing to combat external fragmentation. The allocator keeps track of the number of free blocks in each memory chunk returned by the operating system. Whenever a c...
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- Spring '10
- The American