[ale] top and SWAP

[Rev. Johnny Healey]

Memory Mapped files will use virtual memory but may not be loaded entirely
into physical memory.  I'm pretty sure that most shared libraries are loaded
as memory mapped files so that the code is only swapped in as needed.

-Johnny

On 9/7/07, John Wells <jb at sourceillustrated.com> wrote:
>
> Guys,
>
> Would like some help in clarifying the SWAP column under top (you might
> have to add it to your view). For example, currently I see:
>
> Tasks: 147 total,   4 running, 143 sleeping,   0 stopped,   0 zombie
> Cpu(s):  0.2%us,  0.1%sy,  0.0%ni, 99.1%id,  0.0%wa,  0.0%hi,  0.6%si,
> 0.0%st
> Mem:   2074688k total,  1810620k used,   264068k free,   462408k buffers
> Swap:  4104568k total,        0k used,  4104568k free,   585468k cached
>
>   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  SWAP COMMAND
> 10362 wellsj    23   0  851m 222m  27m S    0 11.0   0:44.24 629m java
> 8822 wellsj    18   0  647m  20m 6288 S    0  1.0   0:01.09 627m java
> 6895 www-data  24   0  225m 2304 1004 S    0  0.1   0:00.00 223m apache2
> 6897 www-data  23   0  225m 2308 1008 S    0  0.1   0:00.00 223m apache2
> 7093 wellsj    15   0  153m  30m  15m R    0  1.5   0:10.54 122m
> gnome-panel
> 7394 wellsj    15   0  334m 211m  23m S    0 10.5   7:58.76 122m
> firefox-bin
> 9809 wellsj    15   0  158m  51m  25m S    0  2.5   0:10.71 106m epiphany
> 6452 mysql     25   0  124m  20m 5012 S    0  1.0   0:00.19 104m mysqld
> 7099 wellsj    18   0 87028  18m  14m S    0  0.9   0:08.65  66m nautilus
> 7231 wellsj    15   0 63340 8708 7056 S    0  0.4   0:00.16  53m
> trashapplet
> 7277 wellsj    16   0 65776  11m 9220 S    0  0.6   0:00.33  52m
> gweather-apple
> 7184 wellsj    15   0 58296 6368 5120 S    0  0.3   0:00.08  50m
> evolution-data
> 7444 wellsj    15   0 69272  20m  10m S    0  1.0   0:03.53  47m
> gnome-terminal
>
>
> Ok, so it appears that some processes are doing some heavy swapping. But,
> look above...in the header section. Swap: says there's a lot available, but
> *none* in use? Where's all that memory in SWAP disappearing to?
>
> I suppose the "cached" memory might have something to do with it, but have
> found no good docs describing what it indicates yet. Given that, I'm hoping
> it's something obvious to a person with good virtual memory understanding
> and am off to read on Wikipedia. However, if *you* know, I'd appreciate your
> insight.
>
> Thanks!
> John
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