Why is the SWAP listed in the detailed list of the TOP command larger than in the summary?
TOP command result:
Mem: 3991840k total, 1496328k used, 2495512k free, 156752k buffers **Swap**: 3905528k total, **3980k** used, 3901548k free, 447860k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ **SWAP** COMMAND 28250 www-data 20 0 430m 210m 21m R 63 5.4 0:07.29 **219m** apache2 28266 www-data 20 0 256m 40m 21m S 30 1.0 0:01.94 **216m** apache2 28206 www-data 20 0 260m 44m 21m S 27 1.1 0:10.27 **215m** apache2 28259 www-data 20 0 256m 40m 21m S 26 1.0 0:02.21 **216m** apache2
The details list shows that a group of apache2 processes are using approximately 210m+ of SWAP memory, but the summary report is only using 3980k. The total SWAP memory in the detailed list is much larger than in the summary. Do these two swaps refer to the same thing?
Solution
Quote from http://www.linuxforums.org/articles/using-top-more-efficiently_89.html :
VIRT=RES+SWAP
As explained previously, VIRT includes anything inside task’s
address space, no matter it is in RAM,
swapped out or still not loaded from
disk. While RES represents total RAM
consumed by this task. So, SWAP here
means it represents the total amount
of data being swapped out OR still not
loaded from disk. Don’t be fooled by
the name, it doesn’t just represent
the swapped out data.