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 *
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 *
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 * The slab allocator supports per-CPU caches ('magazines') to facilitate
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 * The slab allocator supports per-CPU caches ('magazines') to facilitate
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 * good SMP scaling.
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 * good SMP scaling.
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 *
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 *
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 * When a new object is being allocated, it is first checked, if it is
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 * When a new object is being allocated, it is first checked, if it is
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 * available in CPU-bound magazine. If it is not found there, it is
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 * available in a CPU-bound magazine. If it is not found there, it is
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 * allocated from CPU-shared slab - if partial full is found, it is used,
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 * allocated from a CPU-shared slab - if a partially full one is found,
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 * otherwise a new one is allocated.
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 * it is used, otherwise a new one is allocated.
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 *
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 *
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 * When an object is being deallocated, it is put to CPU-bound magazine.
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 * When an object is being deallocated, it is put to a CPU-bound magazine.
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 * If there is no such magazine, new one is allocated (if it fails,
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 * If there is no such magazine, a new one is allocated (if this fails,
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 * the object is deallocated into slab). If the magazine is full, it is
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 * the object is deallocated into slab). If the magazine is full, it is
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 * put into cpu-shared list of magazines and new one is allocated.
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 * put into cpu-shared list of magazines and a new one is allocated.
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 *
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 *
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 * The CPU-bound magazine is actually a pair of magazine to avoid
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 * The CPU-bound magazine is actually a pair of magazines in order to avoid
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 * thrashing when somebody is allocating/deallocating 1 item at the magazine
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 * thrashing when somebody is allocating/deallocating 1 item at the magazine
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 * size boundary. LIFO order is enforced, which should avoid fragmentation
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 * size boundary. LIFO order is enforced, which should avoid fragmentation
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 * as much as possible.
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 * as much as possible.
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 *  
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 *  
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 * Every cache contains list of full slabs and list of partialy full slabs.
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 * Every cache contains list of full slabs and list of partially full slabs.
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 * Empty slabs are immediately freed (thrashing will be avoided because
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 * Empty slabs are immediately freed (thrashing will be avoided because
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 * of magazines).
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 * of magazines).
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 *
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 *
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 * The slab information structure is kept inside the data area, if possible.
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 * The slab information structure is kept inside the data area, if possible.
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 * The cache can be marked that it should not use magazines. This is used
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 * The cache can be marked that it should not use magazines. This is used
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 * only for slab related caches to avoid deadlocks and infinite recursion
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 * only for slab related caches to avoid deadlocks and infinite recursion
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 * (the slab allocator uses itself for allocating all it's control structures).
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 * (the slab allocator uses itself for allocating all it's control structures).
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 *
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 *
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 * The slab allocator allocates lot of space and does not free it. When
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 * The slab allocator allocates a lot of space and does not free it. When
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 * frame allocator fails to allocate the frame, it calls slab_reclaim().
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 * the frame allocator fails to allocate a frame, it calls slab_reclaim().
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 * It tries 'light reclaim' first, then brutal reclaim. The light reclaim
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 * It tries 'light reclaim' first, then brutal reclaim. The light reclaim
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 * releases slabs from cpu-shared magazine-list, until at least 1 slab
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 * releases slabs from cpu-shared magazine-list, until at least 1 slab
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 * is deallocated in each cache (this algorithm should probably change).
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 * is deallocated in each cache (this algorithm should probably change).
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 * The brutal reclaim removes all cached objects, even from CPU-bound
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 * The brutal reclaim removes all cached objects, even from CPU-bound
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 * magazines.
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 * magazines.