Swapping(cont) ☆ Context switch Swapped in out cost too much Assume: process size 1MB, disk transfer rate 5MB/sec, average latency 8ms O Transfer time =IMB/(SMB/sec)=1/5 sec=200 ms Swap time =208 ms ● Swap out&i=416 958 Major part of swap time is transfer time For rr scheduling, time quantum should > 416ms Problems exist for pending 1/0 processes swapping 嵌入式系统实验室 EM目 EDDED SYSTEM LA口RAT口RYSwapping (cont.) ❖ Context switch ➢ Swapped in & out cost too much ➢ Assume: process size 1MB, disk transfer rate 5MB/sec, average latency 8ms ⚫ Transfer time =1MB / (5MB/sec) = 1/5 sec = 200 ms ⚫ Swap time = 208 ms ⚫ Swap out & in = 416 ➢ Major part of swap time is transfer time ❖ For RR scheduling, time quantum should >> 416ms ❖ Problems exist for pending I/O processes swapping