[CentOS] Swap memory: I can't reconcile this stuff.

[Feizhou]

Sam Drinkard wrote:
> 
> 
> William L. Maltby wrote:
> 
>> I need to look more into it, but before I start the long and arduous
>> "googling my life away" process, I figured someone might know the
>> answer. I've read the man pages several times and they didn't change!
>> :-(
>>
>> As normal, while looking at one thing, something else bites my butt. I
>> tuned on the swap field in top and sort on it. Here's an edited snippet
>> of the results.
>>
>> Mem:    775708k total,   764752k used,    10956k free,    60780k buffers
>> Swap:  1572856k total,      160k used,  1572696k free,   377324k cached
>>
>>  PID  VIRT  RES  SHR %MEM SWAP COMMAND
>> 24729  127m  32m  15m  4.3  94m evolution
>> 3409 97220 5268 4304  0.7  89m evolution-data-
>> 2851  115m  36m 7120  4.8  79m X
>> 10937  109m  45m  14m  6.0  63m firefox-bin
>> 3417 63076 7876 6756  1.0  53m evolution-alarm
>> 3363 40332 7284 6228  0.9  32m eggcups
>> 24745 37480 8176 6876  1.1  28m evolution-excha
>> 3736 53272  29m 8660  3.9  22m gnome-terminal
>> 3361 44404  21m  10m  2.9  21m nautilus
>> 3357 39868  21m  10m  2.8  17m gnome-panel
>> 4096 25460 7600 5960  1.0  17m gkrellm
>> 3373 20488 3492 2944  0.5  16m gnome-vfs-daemo
>> 3367 43608  26m  10m  3.4  16m rhn-applet-gui
>> 3359 19904 6128 5316  0.8  13m gnome-volume-ma
>> 3387 20904 8068 6696  1.0  12m clock-applet
>> 3389 19456 6648 5696  0.9  12m notification-ar
>> 3316 19080 7140 5960  0.9  11m gnome-settings-
>> 3385 22304  10m 7576  1.4  11m mixer_applet2
>> 3244 21508 9960 6868  1.3  11m gnome-session
>> 4144 22476  10m 7456  1.4  11m wnck-applet
>> 2587 12412 2364 1940  0.3 9.8m gdm-binary
>> 2846 13220 3340 2728  0.4 9880 gdm-binary
>> 3365 13812 4532 3920  0.6 9280 pam-panel-icon
>> 3355 14768 7524 5984  1.0 7244 metacity
>> 7182 10328 3436 2280  0.4 6892 sendmail
>> 18501 11080 4248 1912  0.5 6832 cupsd
>>
>> Note that the summary line says 160k of swap is used. The man pages say
>> the summary and the details under "SWAP" are both reported in "k". No
>> mention of "m" is made, I presume that it means "megabytes"?
>>
>> If so, I can't reconcile what I'm seeing. Free seems to support the
>> summary lines.
>>
>>             total       used       free...
>> Mem:        775708     764772      10936...
>> -/+ buffers/cache:     326584     449124
>> Swap:      1572856        160    1572696
>>
>> Cat of /proc/meminfo also seems to support the summary lines.
>>
>> SwapTotal:     1572856 kB
>> SwapFree:      1572696 kB
>>
>>
> Looked at the same top info, and I don't understand what I see either.  
> With processes running, I'm seeing close to 500mb of stuff swapped out, 
> but according to free, only the 2.2 mb is swapped.  There's gotta be 
> more to this than meets the eye, or something is lying about the swap.  
> The system monitor also shows only 2.2mb of swap in use, so where is top 
> getting this 500+ mb of swap data from?

most of the 'swapped' data is probably sitting in the cache or buffers?

Here is an example:

https://bugzilla.redhat.com/bugzilla/attachment.cgi?id=129064