OS Notes

1.     The minimum number of frames per process (in a demand paged environment) is defined by the computer architecture (or instruction set architecture), whereas the maximum number is defined by the amount of available physical memory.

2.     In any case, we are faced with three major components of the page-fault service time:

1. Service the page-fault interrupt.

2. Read in the page.

3. Restart the process.

3.     The Hardware for demand paging is same as that for paging. Hardware does mapping of logical to physical address plus provides protection and legality of address space.

4.     Number of page faults on a reference string S in LRU is same when S is reversed and LRU is used on it too. Same is the case for optimal page replacement strategy

5.     Dispatcher is looks to see if the desired process to be scheduled by the scheduler is available in memory or not. If not then it swaps out some process and swaps in the desired process.