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Swap usage by top and free command doesn't match

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# 1  
Old 02-08-2012
Swap usage by top and free command doesn't match
Its rather confusing, the output of top command is below:

Quote:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ SWAP COMMAND
25303 mysql 15 0 2968m 708m 4948 S 38.2 9.0 225:26.20 2.2g mysqld

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:

Quote:
[root@server ~]# free
total used free shared buffers cached
Mem: 8046000 7476800 569200 0 296012 5291468
-/+ buffers/cache: 1889320 6156680
Swap: 4192956 61320 4131636

[root@server ~]# swapon -s
Filename Type Size Used Priority
/dev/cciss/c0d0p2 partition 4192956 61320 -1


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.. Smilie
# 2  
Old 02-08-2012
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:
Code:
grep "VmSwap" /proc/PID_OF_PROCESS/status

The output is in bytes. Smilie
# 3  
Old 02-08-2012
Yes it is RHEL. But why is the discrepancy between the top and free command output?
# 4  
Old 02-08-2012
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.
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