in Variable Partitions Hardware requirements base register and limit register

Solve the external fragmentation problem by making the units small

Page size is often a power of 2

in Address translation physical address is PFN+offset

The (M) Modify bit says whether the page has been accessed

The(V) Valid bit says whether or not the PTE can be used

The virtual page number (VPN) determines physical page

A simple technique is a three-level page table

in Two-Level Page Tables Virtual addresses (VAs) have three parts

in Paging Limitations Can still have External fragmentation

segmentation = 1 segment/process

segmentation = many segments/process

page (logical) => page frame (physical)

in Hardware support multiple base/limit pairs, two per segment

Cooperative Process: One process's execution has an effect on the execution of other processes.

Independent Process: the execution of one process has impact on the execution of the others

Processes can execute concurrently or in series

multi-core processor allows parallel execution of different processes

Process Synchronization is the task of coordinating the execution of processes in such a way that two processes can have access to the same shared data and resources

Race Condition is Several processes access and manipulate the same data concurrently may lead to incorrect shared data.

The Producer-Consumer problem is a classic multi-process synchronization problem.