Memory Management Tutorial
Section 2.4 - Other Memory Allocation Methods
In addition to sequential-fit and buddy methods, there are many ad hoc approaches to memory management. If the application is sufficiently complex, it might be desirable to break available memory into several memory zones, each with a different memory management scheme. For example, some zones might have a simple memory access pattern of first-in, first-out. This zone can therefore be managed efficiently by using a simple stack. Another zone might allocate only records of fixed size, and so can be managed with a simple freelist. Other zones might need one of the general-purpose memory allocation methods discussed in this section. The advantage of zones is that some portions of memory can be managed more efficiently. The disadvantage is that one zone might fill up while other zones have excess memory if the zone sizes are chosen poorly.
Another approach to memory management is to impose a standard size on all memory requests. We have seen an example of this concept already in disk file management, where all files are allocated in multiples of the cluster size. This approach leads to internal fragmentation, but managing files composed of clusters is easier than managing arbitrarily sized files. The cluster scheme also allows us to relax the restriction that the memory request be serviced by a contiguous block of memory. Most disk file managers and operating system main memory managers work on a cluster or page system. Block management is usually done with a buffer pool to allocate available blocks in main memory efficiently.