Swap usage by top and free command doesn't match

proactiveaditya · February 8, 2012, 5:40pm

Its rather confusing, the output of top command is below:

The "swap" field of top is described by the manpage as: "The swapped out portion of a task's total virtual memory image."

But the output of free command suggests something else and it does tally with the output of swapon command:

So why is this discrepancy? How would i determine which process is using how much swap?

---------- Post updated at 05:40 PM ---------- Previous update was at 03:05 AM ----------

Any help will be highly appreciated..

admin_xor · February 8, 2012, 5:56pm

What is the OS you are using?
If it's a Linux operating system, you can easily find the swap memory used by a process with the following:

grep "VmSwap" /proc/PID_OF_PROCESS/status

The output is in bytes.

proactiveaditya · February 8, 2012, 6:01pm

Yes it is RHEL. But why is the discrepancy between the top and free command output?

admin_xor · February 8, 2012, 6:14pm

This entirely depends on the perspective the program is looking from. Not only free top, people found discrepancies among the outputs of sar -r, vmstat, ps aux.

But, as far as my knowledge goes, free command shows output using /proc/meminfo file. That's a direct output from kernel and ought to be more correct one.