伙伴系统:avail[0..m]为可利用空间表, n为申请分配量, 若有不小于n的空闲块, 则分配相应的存储块, 并返回其首地址,否则返回NULL -Partner system: avail [0 .. m] can be used for table space, n for the distribution of the volume of applications, if n is not less than the free block, then the distribution of the corresponding storage block, and return to its first address, otherwise return NULL