physical and virtual memory management
physical memory(DRAM)
virtual vs. Physical memory
allocate
– allocation replacement
arbitrate
– address translation and validation
Page-based memory management
Allocate => pages -> page frames
Arbitrate => page tables
Segment-based memory management
Allocate segment
Arbitrate segment registers
CPU package (cpu, mmu) => main memory
MMU
-> translate virtual to physical addresses
-> reports faults: illegal access, permission
Cache – translation lookaside buffer
– valid VA-PA translations:TLB
pages(VPN:offset) – page table “map” (PEN:offset) – DRAM
Page Table Entry
page frame number x w r a d p
Flags
– present(valid/invalid), Dirty(written to), accessed(for read or write)
Page Fault
32-bit architecture
– page table entry
=> 4 bytes, including PEN + flags
– virtural page number(VPN)
=> 2^32 / page size
– page size
=> 4 KB
