Performance Example (cont).
So: What is a good page fault rate?
Effective Access Time = 107* (1-p) +( 100,000+ 10,000,000+0.5*10,000,000+20,000+205)*p
EAT = 107 *(1-p) + 15,120,205*p.
Suppose p is 1% ? EAT = 151,309
Talking about a slowdown of 1414!!!
For the luxury of Virtual Memory to cost only 10% overhead, we need p to be around 0.00000066 !!!!.
This means one page fault for every 1,500,000 memory accesses !!!