OPERATING SYSTEMS LESSON 3 Flashcards
is a technique that allows the execution of processes that may not be completely
in memory.
VIRTUAL MEMORY
The main visible advantage of this scheme is that programs can be larger than physical memory.
VIRTUAL MEMORY
Further, Virtual Memory abstracts main memory into mainly __________________ as viewed by the user from physical memory.
extremely large, uniform array of storage separating logical memory
This technique frees programmers from concern over memory storage limitations.
Virtual Memory
This technique frees programmers from concern over __________________________
memory storage limitations.
Virtual memory is not easy to implement,
however and may substantially _____________ if used carelessly
DECREASE PERFORMANCE
This is the separation of use logical memory from physical memory
Virtual Memory
Virtual Memory separation allows an
extremely large virtual memory to be provided for programmers when only a _________________
smaller physical memory is
available.
Virtual memory is commonly implemented by __________________
Demand Paging
Virtual memory can also commonly be implemented by __________________
Segmentation System
Several systems provide a paged segmentation scheme where segments are broken into _____________________
Pages
_________________is similar to a paging system but with swapping.
Demand-Paging System
In this virtual memory implementation, processes reside in ________________ ( which is usually a ___________)
Secondary Memory, Disk
. When we want to execute a process, we ________it into __________
Swap, Memory
When a _____________is to be swapped in, the __________ guesses which page will be used before the process is swapped out again.
Process, Pager
Instead of swapping in a whole process, the pager brings only those ________ Into memory.
necessary pages
Demand Paging avoids reading into _______________ that will not be used anyway, decreasing the swap time and the amount of _________________ needed.
memory pages , physical memory
With __________________, we need some form of _____________ support to distinguish between those pages that are on the disk.
Demand Paging, hardware
When this bit is set to “_______”, this value indicates that the page is either __________ or _________ but not currently in disk
Valid, Not Valid, Valid
Meaning of:
Valid Bit and Not Valid Bit
a Not in the logical address space of the process.
b currently on the disk.
The _________________ for a page that is brought into memory is set
as usual,
page table entry