Using memory maps

Virtual memory is a representation of the combined physical memory and swap space in a system. It enables running processes to access more than the existing physical memory by mapping locations in physical memory to files on disk. When the system needs more pages of memory than are available, some of the existing pages will be paged out or written to the swap space.

The memory map displays the total virtual memory use of the process, and can be used to determine the memory cost of running a single or multiple instances of the program, to ensure the use of the correct shared libraries, to see the results of adjusting various performance tuning parameters the program may have, or to diagnose issues such as memory leaks.

Reading the memory map

Addresses are diplayed in hexadecimal (base 16).

Sizes are displayed in IEC binary prefixes.

At runtime the process can allocate more memory dynamically into an area called the heap, and store arguments and variables into another area called the stack.

The program itself and each of the shared libraries has three entries each, one for the read-execute text segment, one for the read-write data segment and one for a read-only data segment. Both data segments need to be paged out at swap time.

Properties

Numele fișierului	Locația bibliotecii comune care este folosită în prezent de proces. Dacă acest câmp este liber, informațiile despre memorie din acest rând descriu memoria care este deținută de procesul al cărui nume este afișat deasupra tabelului hartă de memorie.
VM Start	The address at which the memory segment begins. VM Start, VM End and VM Offset together specify the location on disk to which the shared library is mapped.
VM Sfârșit	Adresa la care segmentul de memorie se termină.
VM Dimensiune	Dimensiunea segmentului de memorie.
Steaguri	Următoarele opțiuni descriu modurile diferite ale accesului memoriei-segment pe care procesul le poate avea: <gui>p</gui> Segmentul de memorie este privat față de proces și nu este accesibil altor procese. <gui>r</gui> Procesul are permisiunea de a citi din segmentul de memorie. <gui>s</gui> Segmentul de memorie este partajat cu alte procese. <gui>w</gui> Procesul are permisiunea de a scrie în segmentul de memorie. <gui>x</gui> Procesul are permisiunea de a executa instrucțiunile care sunt conținute în segmentul de memorie.
VM Compensație	The location of the address within the memory segment, measured from VM Start.
Private, Shared, Clean, Dirty	private pages are accessed by one process shared pages can be accessed by more than one process clean pages have not yet been modified while in memory and can be discarded when designated to be swapped out dirty pages have been modified while in memory and must be written to disk when designated to be swapped out
Dispozitiv	The major and minor numbers of the device on which the shared library filename is located. Together these specify a partition on the system.
Inode	The inode on the device from which the shared library location is loaded into memory. An inode is the structure the filesystem uses to store a file, and the number assigned to it is unique.