Processs Address Space Linux Address Space 0x7fffffff Stack Data - - PDF document
10/21/2014 Processes, Address Spaces, and PROCESS Memory Management A running program and its associated data Jonathan Misurda jmisurda@cs.pitt.edu Processs Address Space Linux Address Space 0x7fffffff Stack Data (Heap) Data (Heap)
Jonathan Misurda jmisurda@cs.pitt.edu
Stack Data (Heap) Text (Code) 0x7fffffff Data (Heap) Globals
– Find the first free block, starting from the beginning, that can accommodate the request
– Find the first free block, starting where the last search left off, that can accommodate the request
– Find the free block that is closest in size to the request
– Find the free block with the most left over after fulfilling the allocation request
– Keep several lists of free blocks of common sizes, allocate from the list that nearest matches the request
A B C D
11111100 00111000 01111111 11111000
8 16 24 32 Memory regions Bitmap
A B C D Memory regions
A 6 ‐ 6 4 B 10 3 ‐ 13 4 C 17 9 ‐ 29 3 D 26 3
8 16 24 32
A X B A X X B X A B A B
_end brk $sp Stack Heap Globals Unallocated Space
Size 16 Size 4 Size 4 Size 8 Size 8 Size 8 Size 2 Size 2 Size 4 Size 8 Size 2 Size 2 Size 4 Size 8
Allocation of size 2 in a region of size 16
Size 2 Size 2 Size 4 Size 8
Allocation of size 4 in a region of size 16
Size 2 Size 2 Size 4 Size 8
Size 4 Size 4 Size 8 Size 2 Size 2 Size 4 Size 8 Size 2 Size 2 Size 4 Size 8
Free region of size 2 in a region of size 16 Mark region as free Combine with “buddy”
Size 4 Size 4 Size 8
Free region of size 1 in a region of size 16 Mark region as free Combine with “buddies”
Size 4 Size 4 Size 8 Size 16 Size 8 Size 8