程序的地址空间：虚地址空间 USTC Virtual address space Physical address space 0x00000000 swap out 0☐1☐ 2☐3☐ 0x00010000 4白5白6白7白 text 0x00000000 program A 8☐9☐10☐11☐ 0x10000000 12☐13☐14☐15☐ data swap in 16☐17日1819日 program 20☐21☐22☐23■ B 虚存：磁盘交换区(swap space) MainMemory 换入/换出时机？ Oxooffffff Demand Paging策略 stack Bring a page into memory only page belonging to process when it is needed 0x游 page not belonging to process 1.Less I/O needed 2.Less memory needed 3.Faster response 4.More users程序的地址空间：虚地址空间 虚存：磁盘交换区（swap space） 换入/换出时机？ Demand Paging策略 Bring a page into memory only when it is needed 1. Less I/O needed 2. Less memory needed 3. Faster response 4. More users