CSE 120 Lecture Notes - Lecture 9: Logical Address
Document Summary
Problems w/ sharing memory: addressing problem - generates memory references, protection - modifying another process" memory. A process executing might actually run some other process (because it"s sharing memory: space - the more processes there are, the less memory each individual can have. The more sharing, the less each gets! (so sharing is not caring) Address spaces - set of addresses for memory. Problem: some addresses don"t exist at the time when the processes start running! Only when you actually need to access the physical memory, convert it. Adder adds base of these logical addresses to translate to physical. Add to base : invalid address, trap (invoke the kernel!) Processes can"t reach back (which is why the kernel is placed at the beginning) Kernel must be protected from all processes (i. e. put it at 0) Each segment has an identifier, s , and a size n s. Logical addresses are of the form (s, i)