What is virtual memory in Linux top?

VIRtual column of the top, refers to the super-space (super consumption space) of the process, which the process might not be actually taking at the run time. There is another column RESident , which refers to the actual physical memory/space allocated by the process, at the runtime.

What is RES memory in top command?

RES stands for the resident size, which is an accurate representation of how much actual physical memory a process is consuming. (This also corresponds directly to the %MEM column.) This will virtually always be less than the VIRT size, since most programs depend on the C library.

What is SHR top?

t: SHR — Shared Mem size (kb) The amount of shared memory used by a task. It simply reflects memory that could be potentially shared with other processes. u: nFLT — Page Fault count The number of major page faults that have occurred for a task.

What is virtual memory Htop?

The virtual memory these programs (htop and the like) are counting is just the size of the address space the processes have requested. You have physical memory, actual RAM, and a virtual address space which maps addresses as user space programs see them to physical memory.

Why does Linux use virtual memory?

Linux supports virtual memory, that is, using a disk as an extension of RAM so that the effective size of usable memory grows correspondingly. The kernel will write the contents of a currently unused block of memory to the hard disk so that the memory can be used for another purpose.

How do I find physical and virtual memory in Linux?

How to Check Memory Usage in Linux, 5 Simple Commands

1. cat Command to Show Linux Memory Information.
2. free Command to Display the Amount of Physical and Swap Memory.
3. vmstat Command to Report Virtual Memory Statistics.
4. top Command to Check Memory Use.
5. htop Command to Find Memory Load of Each Process.

Why is virtual memory so high?

Virtual memory is simulated RAM. When all of the RAM in a machine being is used, the computer shifts data to an empty space on the hard drive. The computer swaps data to the hard disk and back to the RAM as needed. When virtual memory is increased, the empty space reserved for RAM overflow increases.

What does virtual memory size in top mean in Linux?

Paging is usually more efficient, and that’s what Linux does, but traditional Linux terminology talks about swapping anyway. “VIRT” just address space, RES is the “real” memory, but the “SHR” (=shared) amount of “RES” is the part of RES that is shared with other processes.

Which is the best command to check memory usage in Linux?

Generally, we look at the memory usage using the free command that provides us the total physical memory and used memory out of total memory. But top command is more useful to check memory usage in Linux. The free command display only physical memory usage but top display virtual memory usages by each process.

How to sort top result on virtual memory on RedHat Linux?

There is an interactive key “M” to sort by memory, which seems to be sorting on resident memory. Is there a way to sort on virtual memory? I happen to be working on Redhat Linux, but the question is not specific to this distribution.

How to sort by memory in Linux howtouselinux?

1 press shift+m after running the top command 2 sort mem usage per process in the interactive menu. More details below. 3 run command top -o +%mem