9 votes 9 votes Suppose: TLB lookup time = 20 ns TLB hit ratio = 80% memory access time = 75 ns swap page time = 500,000 ns 75% of pages are dirty OS uses a 3 level page table What is the effective access time (EAT) if we assume the page fault rate is 15% ? Operating System operating-system demand-paging memory-management multilevel-paging + – biranchi asked Jan 25, 2017 • retagged May 22, 2020 by soujanyareddy13 biranchi 4.7k views answer comment Share Follow See 1 comment See all 1 1 comment reply Bikram commented Aug 26, 2017 reply Follow Share Indeed 75140 is correct answer .. see this why it is correct http://www.cs.jhu.edu/~yairamir/cs418/os5/tsld028.htm 0 votes 0 votes Please log in or register to add a comment.
Best answer 13 votes 13 votes EAT=No Page Fault(TLB hit+TLB miss)+ Page Fault (TLB hit+TLB miss+ Page swap time) =0.85(0.8(20+75)+0.2(20+3$\times$75+75))+0.15(0.8(20+75)+0.2(20+3$\times$75+75)+500000) =119+75021=75140 ns srestha answered Jan 25, 2017 • edited Apr 27, 2019 by srestha srestha comment Share Follow See all 41 Comments See all 41 41 Comments reply Show 38 previous comments srestha commented Nov 25, 2019 reply Follow Share How much r u getting then? 0 votes 0 votes suvradip das commented Mar 13, 2020 reply Follow Share @baljeetkaur you are absolutely on point. Since the page is dirty we need two spaps and one swap for a non dirty page. @sreshtha youre answer may have matched but you did like this for otyher test series question. 0 votes 0 votes sachin486 commented Sep 5, 2020 reply Follow Share I don’t understand why in page fault (0.15) TLB hit time is considered….because in case of page fault obviously 100% there will be TLB miss 0 votes 0 votes Please log in or register to add a comment.
4 votes 4 votes we can also solve like this - Prateek Raghuvanshi answered Aug 26, 2018 • edited Aug 26, 2018 by Prateek Raghuvanshi Prateek Raghuvanshi comment Share Follow See all 8 Comments See all 8 8 Comments reply Show 5 previous comments Prateek Raghuvanshi commented Nov 5, 2018 reply Follow Share Why are you relating this to page fault ??we need page tables for address translation,we are not considering page fault . 0 votes 0 votes 3lurryface commented Dec 31, 2019 reply Follow Share @Gurdeep Saini that is my doubt for almost one year from now that why there is no page fault while accessing multi-level page tables. It is only possible if all the pages of inner page tables are present in memory all the time but then what is the use of multilevel paging when we need to store whole inner page tables in memory it makes no sense at all. 0 votes 0 votes suvradip das commented Mar 13, 2020 reply Follow Share @prateek since the page is dirty the definitely we need two swaps, one swap for writing the page onto the secondary memory and another onr for getting the new page into the main memory. Hence the effective Page fault service time = (dirty page *(time to service a dirty page main memory access time) + no dirty page( time to service a non dirty page + main memory access time) =(0.75( 2*500,000 + 75) + 0.25(500,000 + 75)) ns 0 votes 0 votes Please log in or register to add a comment.
0 votes 0 votes https://gateoverflow.in/?qa=blob&qa_blobid=2405338696923312454 ayushsomani answered Jul 26, 2019 ayushsomani comment Share Follow See all 0 reply Please log in or register to add a comment.
0 votes 0 votes EAT=No Page Fault(TLB hit+TLB miss)+ Page Fault (TLB hit+TLB miss+ Page swap time + dirty pages x page swap time) =0.85[ 0.8(20+75)+0.2(20+3×75+75) ]+0.15[ 0.8(20+75)+0.2(20+3×75+75)+500000 +.75x500000 ] =93890 ns reference question – https://gateoverflow.in/77917/testbook-os-test sachin486 answered Sep 12, 2020 • edited Sep 13, 2020 by sachin486 sachin486 comment Share Follow See all 0 reply Please log in or register to add a comment.