Single-Level Page Table ·31 ·12·11 ·0 Virtual .value =x Address .value =y 32 bits 单级页表太大， 且需要连续内存存放！ 220 page table 212 entries data entries page frame TTOTTTO Size of page table 8 bits =220 32 bits =4 Mbytes Size of page =212 8 bits =4 Kbytes 2:48-bit canonical form virtual addresses and 4 KB pages.On such a system,it would take 2048 B/2012 B *8 B=2039 B=512 GB of storage just for the page table alone!Single-Level Page Table page frame page frame Virtual Address •31 •12•11 •0 page table page frame data •value = y •y 2 20 entries 32 bits 2 12 entries Size of page table = 220 * 32 bits = 4 Mbytes •value = x •x 8 bits Size of page = 212 * 8 bits = 4 Kbytes 例2：48-bit canonical form virtual addresses and 4 KB pages. On such a system, it would take 2^48 B / 2^12 B * 8 B = 2^39 B = 512 GB of storage just for the page table alone! 单级页表太大， 且需要连续内存存放！