real / virtual memroy

[j773303]

What's the meaning of real memory and virtual memory? Does virtual memory is swap? Thanks.

[Mark Grant]

Real memory is physical memory i.e. Those little black chips inside the computer. virtual memory is real memory plus anything else that the system can access as if it was real memory. Practically this really means swap but theoretically could include anything, even a tape if you could persuade the kernel to think a tape was an area of RAM though this would be very slow memory :)

[Sanjay Kumar Suri]

Real/Physical memory is the RAM installed.

Physical memory may be supplemented by specially configured space on disk known as swap/Virtual memory.

sks

[John Carr_2]

Hi

real is something you can physically hold in your hand ( RAM) while virtual is something you have configured for memory usually swap on a disk

:-) John.

[j773303]

So, virutual memory in top command is the swap space?

[Mark Grant]

yes, practically speaking.

[Sanjay Kumar Suri]

Yes.

Memory Data Includes virtual and real memory in use (with the amount of memory considered "active" in parentheses) and the amount of free memory.

sks

[Elmar P. Kolkman]

Some things to bear in mind:
1) virtual memory includes the real/physical memory. So if you have 1Gb physical and 3 Gb swap, virtual would be about 4 Gb (see point 2).
2) top and other commands might report real/physical memory excluding the memory that's used by the kernel. So if you have 1 Gb physical memory and your kernel is 300 Mb, it will report as 724Mb real.

To be sure about the physical parameters of a system, use tools like stm or print_manifest.