Self Doubt [Effective memory access time]

Question

Page fault rate = p

Main memory access time  = m

Page fault service time = PS

EMAT = (1-p) (m) + (p) (PS + m)

OR

EMAT = (1-p) (m) + (p) (PS)

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which one is right ...if page fault occurs should we consider [ Page fault service time + MM ]  OR [  Page fault service time only  ]

 

Comments

@Ayush Upadhyaya

@Shaik Masthan

 

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it's depend upon definition of page fault service.

if page fault service means, Accessing the page in secondary memory + Loading the page in main memory + Accessing the page in Main memory

then your second formula EMAT = (1-p) (m) + (p) (PS) is right 

 

if page fault service means, Accessing the page in secondary memory + Loading the page in main memory

then your first formula EMAT = (1-p) (m) + (p) (PS+M) is right 

 

but it is not mentioned clearly which one is correct !

while solving the answer, apply Both formulas, one of them should be in the answer,

if both answers in the options, go with you preffered one !

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this will help you https://gateoverflow.in/148292/os-page-fault-service-time-vs-effective-memory-access-time

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WHat about numerical answer type..mostly EMAT questions are numerical answer type

Can you please Check this :

EMAT  =  [ VA  --> PA ] + Memory access after getting PA

 

1) VA --> PA ==> Ht( tlb time ) + (1-Ht)(tlb time + k* m )

After this we will get Page table entry ...At that very moment we can figure out Page fault / not by looking V / I bit \

 

2) If no page fault ==> Memory access after getting PA ==> m

 

3) If page fault Memory access after getting PA =>(1-p) (m) + p(Page fault service time)

| PS = Accessing the page in secondary memory + Loading the page in main memory + Accessing the page in Main memory

 

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i also follow this method only