Test 2 Flashcards
Linux Memory Area
- a chunk of virtual memory mapped to a VM area space structure
task_struct
- The OS stores process state in a data structure called process control block. There is one per process
called task_struct in linux
Difference between segmentation fault and protection fault?
- segmentation fault occurs when request and address is not in the VMA
- protection fault occurs when you don’t have permissions to access that address
memory mapping
- structure of data indicating how memory is laid out
demand zero page
- physical page fill of 0’s
swap file
- same as swap space
- portion of the memory used for virtual memory
swap space
- same as a swap file
- portion of the memory used for virtual memory
copy on write
- copy file and save new only when wrote to otherwise access the same file
demand zero page
- physical page fill with 0’s
What does the mmap function do?
- allows you to comb through a file like it is an array
What is a dynamic memory allocator and what are the two types of memory allocators?
- memory allocator that all allocate explicitly
- there are two types: explicit and implicit
shared object
- a file that contains binary code and data that can be loaded into memory and linked dynamically
shared area
- virtual memory that are shared by more than one process and then can be used by multiple programs simultaneously. Although virtual memory allows processes to have separate address spaces, there are times when you need processes to share memory.
private object
blank
throughput (with respect to memory alloactors)
- how many commands per second
aggregate payload
- this is all the payloads added together
What are the two types of fragmentation?
- internal and external fragmentation
internal fragmentation
- type of fragmentation where the payload is smaller than the block size it is going into
external fragmentation
- type of fragmentation where the payload…space cannot be filled
- to explain more the area that is free in the block cannot be filled by the payload
What are the two types of memory blocks?
- allocated memory and free memory
allocated memory
- allocated memory is memory that is filled
free memory
- free memory is memory that is not yet filled and waiting to be filled
allocated and free blocks
- allocated blocks are blocks that are used up in the memory while free blocks are block that are waiting to be filled in the memory
What are some implementation issues? (just a list for this flash card)
- header, payload, padding, free block organization, block placement, block splitting, block coalescing
What does the malloc do when it cannot satisfy memory requests?
- it returns a NULL
explicit allocator
- explicit allocators explicitly allocates memory
- frees the space
implicit allocator
- implicit allocators explicitly allocates memory
- does not free the space
