RAM
Linux Memory Types
- physical memory - resource containing code and data.
- swap file - optional. Keeps (dirty) modified memory for later use if too many demands are made on physical memory.
- virtual memory - "unlimited" (...)
No matter the memory type - all are managed as pages (typically 4096 bytes)
free (-m to show in MB)
| Header |
Description |
| total |
indicates memory/physical RAM available for your machine. By default these numbers are in KB's |
| used |
indicates memory/RAM used by system. This includes buffers and cached data size as well |
| free |
indicates total unused RAM available for new process to run |
| shared |
indicates shared memory. This column is obsolete and may be removed in future releases of free |
| buffers |
indicates total RAM buffered by different applications in Linux |
| cached |
indicates total RAM used for Caching of data for future purpose |
| -/+ buffers/cache |
shows used column minus (buffers+cached) and free column plus (buffers+cached). Why is that? Because when memory used is getting up to limit, the buffers + cache will be freed and used by demanding applications. This show most accurate memory usage. |
New version of free: |
|
| - buff/cache: sum of buffers and cached |
|
| - available: not exactly free column plus (buffers+cached) |
|
top
| Header |
Description |
| virt |
|
| res |
|
| shr |
|
| %mem |
|