memory management Flashcards
Also known as dynamic partitioning. Only the exact memory space needed by a process is allocated
Variable partition memory allocation strategies
Is a technique wherein only those instructions or data that are currently needed are loaded into main memory
Overlaying
Is a special hardware device used to take care of logical to physical address conversion
Memory management unit
Main memory is divided into 8 fixed, but equal-sized partitions of 4MB each
Fixed equal-sized partitions
Select the smallest partition that will fit an incoming process
Best fit available strategy
32MB main memory is divided into 8 fixed, but unequal-sized partitions
Fixed unequal-sized partitions
If the sized of partition is larger than the size of the process, it leads to wastage of memory known as
Internal fragmentation
It happens when the available partitions are not big enough to accomodate any waiting process
External fragmentation
the OS searches from the beginning of the main memory. The first hole encountered that is large enough for the incoming process will be selected.
First-fit strategy
The operating system searches the entire list of holes for the smallest hole that can accommodate then incoming
process.
Best-fit strategy
the operating system searches the entire list of holes for the largest hole and this will allocated to the incoming
process.
Worst-fit strategy
Strategies used by the operating system in deciding which hole a process will be placed
Firs-fit strategy, Best-fit strategy, Worst-fit strategy
Free memory space
Hole
processes are moved towards the beginning of the main memory. The holes are therefore grouped
together, forming one large block of free memory
Compaction
memory management scheme that allocate the non-contigiuos memory space into process.
Paging
