Slab allocation is a memory management mechanism intended for the efficient memory allocation of objects. In comparison with earlier mechanisms, it reduces fragmentation caused by allocations and deallocations. This technique is used for retaining allocated memory containing a data object of a certain type for reuse upon subsequent allocations of objects of the same type. It is analogous to an object pool, but only applies to memory, not other resources. Slab allocation was first introduced in the Solaris 2.4 kernel by Jeff Bonwick. It is now widely used by many Unix and Unix-like operating systems including FreeBSD and Linux. Basis Slab allocation renders infrequent the very costly practice (in CPU time) of initialization and destruction of kernel data-objects, which can outweigh the cost of allocating memory for them. When the kernel creates and deletes objects often, overhead costs of initialization can result in significant performance drops. Object caching leads to less frequent invocation of functions which initialize object state: when a slab-allocated object is released after use, the slab allocation system typically keeps it cached (rather than doing the work of destroying it) ready for re-use next time an object of that type is needed (thus avoiding the work of constructing and initialising a new object). With slab allocation, a cache for a certain type or size of data object has a number of pre-allocated "slabs" of memory; within each slab there are memory chunks of fixed size suitable for the objects. The slab allocator keeps track of these chunks, so that when it receives a request to allocate memory for a data object of a certain type, usually it can satisfy the request with a free slot (chunk) from an existing slab. When the allocator is asked to free the object's memory, it just adds the slot to the containing slab's list of free (unused) slots. The next call to create an object of the same type (or allocate memory of the same size) will return that memory slot (or some other free slot) and remove it from the list of free slots. This process eliminates the need to search for suitable memory space and greatly alleviates memory fragmentation. In this context, a slab is one or more contiguous pages in the memory containing pre-allocated memory chunks. Implementation Understanding the slab allocation algorithm requires defining and explaining some terms: Cache: cache represents a small amount of very fast memory.