Page Faults

07 Oct 2018 | Less than one-minute read

What happens when there is a page fault?

             (start)
                │                ┌───────────┐                ┌───────────┐
                │ VPN            │   ┌───────┴────────┐       │   ┌───────┴────────┐
                │                │   │  Find on disk  │       │   │   TLB update   │
        ┌───────┴────────┐       │   └───────┬────────┘       │   └───────┬────────┘
        │   TLB Lookup   │       │           │                |           │
        └───────┬────────┘       │           │                |           │
                │                │           │                |           │
                │                │   ┌───────┴────────┐       │   ┌───────┴────────┐
                │                │   │ Read page frame│       │   │     Resume     │
        ┌───────┴────────┐       │   └───────┬────────┘       │   └───────┬────────┘
        │   PT Lookup    │       │           │                |           |
        └───────┬────────┘       │           │                |           |
                │                │           │                |         (end)
                │                │   ┌───────┴────────┐       │
                │                │   │    PT update   │       │
                └────────────────┘   └───────┬────────┘       │
                                             └────────────────┘

         Thread local                   System global              Processor local

If each process has at most one thread, then there is no risk of serialization since each process has it’s own page table. But, if the process has multiple threads, then we need a strategy to avoid ensuring that page fault service doesn’t have serialization.