作者bennylu (减肥)
看板Grad-ProbAsk
标题Re: [理工] [计组]-90台大-average access time
时间Fri Jan 15 17:00:13 2010
※ 引述《steven9374 (steven)》之铭言：
: Virtual memory is often implemented by demand-page.
: Consider an operating system with on-demand paging
: over a single-level page table,where the page table
: of each process always resides in the memory.
: Suspose that the TLB access time,the memory access time,
: and the acerage page-fault service time are 20ns,100ns,25ms,
: respectively.Let the hit ratio of TLB and the page fault
: rate be 98% and 0.0001%,respectively.What is the effective
: access time?
: 答案写=0.98*(20+100)+0.02*(20+100+100)*0.999999+
: 0.02*0.000001*(25+100+25000000)=122.5ns
: 後面实在看不太懂...
: 请求板上大大的教教小弟我
TLB(20)
↙ ↘
Hit(98%) Miss(2%)
↙ ↘
MEM(100) Page Table(100)
↙ ↘
Hit(99.9999%) Miss(0.0001%)
↙ ↘
MEM(100) Page Fault(25000000)
20 + 0.98*100 + 0.02*[ 100 + 99.999%*100 + 0.0001%*25000000 ] = 122.5ns
^^^^^^^=1
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※ 编辑: bennylu 来自: 140.113.207.117 (01/15 17:01)
1F：推 steven9374:那边要直接以1算吗? 01/15 17:19
2F：推 steven9374:感谢这位前辈的热心指导 01/15 17:25