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Translation Lookaside Buffer-1
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Performance Of Paging

Performance of simple  paging:The  main memory access time is  ='m'.

  • page table are stored in main memory then formulae for Effective main memory access time =2*m
  • The tanslation look aside buffer(T.L.B) is added to improve the performance of paging
  • T.L.B  contains the frequently reffered page numbers and corresponding frame numbers.

TLB  access time ='c'

TLB hit ratio='x'

Then the formulae for effective main memory access time =x\ast \left ( c+m )+\left ( 1-x )\left ( c+2m )

Ques : consider a system which has  main memory access time is 100ns and TLB access time is 20ns and TLB hit ratio is 95% then what is the EMMAT with TLB and without TLB.

solution:

with TLB 

EMMAT=x\ast \left ( c+m )+\left ( 1-x )\left ( c+2m )

=0.95\ast \left ( 20+100 \right )+0.05(20+2\ast 100)

=125ns

without TLB

EMMAT=2\ast m

=2\ast 100 ns

=200ns

With TLB the performance is increased in paging

 

Performance of Multilevel  paging:

The  main memory access time is  ='m'.

  • page table are stored in main memory then formulae for Effective main memory access time =3*m
  • The tanslation look aside buffer(T.L.B) is added to improve the performance of paging
  • T.L.B  contains the frequently reffered page numbers and corresponding frame numbers.

TLB  access time ='c'

TLB hit ratio='x'

Then the formulae for effective main memory access time=

x\ast \left ( c+m \right )+\left ( 1-x \right )(c+3m)

For 'n' level paging

EMMAT=x\ast \left ( c+m \right )+\left ( 1-x \right )(c+(n+1)m)

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