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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