Virtual Memory and Page Tables

Question 1

TLB?

Answer 1

translation look-aside buffer (TLB), to keep recent results of virtual page number translations, so that if we need to look up the same virtual page number again, we can look it up quickly in the TLB instead of performing three slow RAM accesses

Question 2

What is trashing?

Answer 2

A situation when a system is spending most of the time in servicing page faults (swapping), than executing the actual process.

Question 3

Whats the purpose of sfence.vma instruction?

Answer 3

When CPU switches to a different process, the content of satp is replaced with the address of the new process’es page table. When it happens, the content of TLB needs to be cleared.
● That is the purpose of RISC-V sfence.vma instruction.