Memory Management Flashcards
Memory divided into allocation units. Each unit is a bit, 0 if the unit is free and 1 if occupied
Memory management with bitmaps
Memory managed via nodes
Memory management with linked lists
Process blocks or holes, indicated via first value in linked list
Memory management with linked lists
Look through all segments until an open hole is found of sufficient size. Use up as much of segment as possible
First fit
Keep pointer to last memory hole and insert into next region (hole or ones after) that can fit memory
Next fit
Take the smallest hole that is adequate
Best fit
Take the largest hole possible
Worst fit
Load first instruction at base address and add base address to all other instructions
Static relocation
Base and limit registers
Intel 8088
Brings program into main memory and runs for certain chunk of time
Swapping
Allows program to run even if only part of program in main memory
Virtual memory
Where virtual addresses are mapped to physical addresses
Memory management unit
What occurs during a page fault
- OS picks page to write with disk
- Bring page with needed address into memory
- Restart instruction
Stores frequently accessed frames in the MMU
Translation Lookaside Buffer
Indicates in TLB that page is in use
valid bit
What occurs during TLB page fault
Page table lookup and evict TLB entry
When page table is not in TLB but is in active memory
Soft miss
Page table is not in TLB but is in disk
Hard miss
Entries = virtual address size / (page size * ram size)
Inverted page table number of entries
2^PT_1 * 2^PT_2 * 2^offset
Total addressable memory in Multi level page table
Each process keeps own page table. Converts virtual page number to physical frame / page address
Regular page table
Virtual page for each occupied physical memory frame
Inverted page table
Easier to map from physical to logical addresses
Inverted page table
Easier to map from logical to physical addresses
Regular page table
If page is written to, before we evict it, must
copy it to disk
