What happens on a TLB miss?

• A. The CPU errors and stops.
• B. The OS resets the TLB to empty without reloading the translation.
• C. The OS performs a page-table walk to obtain the translation, loads it into the TLB, and retries the memory access.
• D. The memory access is retried using the previous translation.

Answer: (C)

When a memory access cannot be translated using the TLB, the system must fetch the missing virtual-to-physical translation from the page tables. This triggers a page-table walk, typically performed by the OS (and sometimes aided by hardware), to locate the page table entry in memory, verify permissions, and then load that translation into the TLB. With the new translation cached, the original memory access is retried using the obtained physical address. If the page isn’t present in memory, a page fault occurs and the OS handles bringing it in. This sequence avoids stalling on a missing translation, instead reusing the faster, cached translation once it’s loaded.