Copy-on-Write Page Fault Count

Problem

Count copy-on-write faults after a process fork.

fork_pages is the set of pages shared by parent and child at fork time, operations contains "read" or "write", and pages gives the page referenced. A write to a shared page faults only the first time, because it then becomes private; reads and non-shared writes never cause a copy fault.

Return the number of copy-on-write faults.

Hint

Once a shared page is copied it is private, so later writes do not fault.

Test cases

case 1

in: [[1,2],["read","write","write","write"],[1,1,1,2]]

expected: 2

case 2

in: [[1],["write","write"],[1,1]]

expected: 1

case 3

in: [[],["write"],[5]]

expected: 0

case 4

in: [[1,2],["read","read"],[1,2]]

expected: 0

case 5

in: [[1],["write"],[2]]

expected: 0

Starter codePython

def cow_page_faults(fork_pages, operations, pages):
    # Your code here
    pass

5 test cases · run your code against them in the editor