typedef struct {

    //当前slab_class的最大item大小
    unsigned int size;      /* sizes of items */
    //当前slab_class每一个slab的item数
    unsigned int perslab;   /* how many items per slab */
    //被释放过的item的list
    void **slots;           /* list of item ptrs */
    //free list大小
    unsigned int sl_total;  /* size of previous array */
    //free list下标 
    unsigned int sl_curr;   /* first free slot */
    //最近申请的page(slab)的指针
    void *end_page_ptr;         /* pointer to next free item at end of page, or 0 */
    //最近申请的page(slab)所剩的item个数
    unsigned int end_page_free; /* number of items remaining at end of last alloced page */
    //当前slab_class申请了多少slab(page)
    unsigned int slabs;     /* how many slabs were allocated for this class */
    //申请的slab的指针数组
    void **slab_list;       /* array of slab pointers */
    unsigned int list_size; /* size of prev array */
    //没用到？
    unsigned int killing;  /* index+1 of dying slab, or zero if none */
    size_t requested; /* The number of requested bytes */

} slabclass_t;