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

Sam Drinkard sam at wa4phy.net
Tue Jun 6 18:46:45 UTC 2006



William L. Maltby wrote:

>
>
>Regardless of that, it sounds like your situation indicates a need to
>run SAR. Turn on your system accounting collection and the reports will
>let you see exactly what's happening with memory, swap, HD, ... and
>when. I presume that these are as good or better than the old UNIX ones
>I remember.
>
>Once you have the bullets, I'm not sure what you might shoot, but you
>ought to kill *something* just for the aggravation you've been
>caused! ;-)
>  
>
Bill,

    After running sar, I'm not sure I'm confused as I was.  I tend to 
think sar might be correct in what it records and sees.  Looking at 
memory usage and swap, I find the system *is* using all of the available 
memory, especially at 0420, most likely when the updatedb and slocate 
crons run.   % memory used is averaging 94.26% and swap peaked at about 
21%, which sort of relates to the 221mb shown by free this morning.  
When the machine is quiescent as it gets, mem usage drops to 72% and 
swap drops to 0.20 %, again, which corresponds with what is reported by 
free and the system monitor applet.  To make a long story short, the 
machine apparetly does need the swap at times, and while it's not using 
much during model run time, the cron jobs do turn it loose!

    Sar can report *alot* of things, and I suspect I'll be using it more 
to see if there is anything I can do to tweak the thing to get a bit 
more performance out of it.  Bad enough that it takes so long for my 
jobs to run, but the number crunching the model does IS pretty tough on 
things I suppose.    Guess we've beat up the swap thing enough.. I'll 
try to learn more about how to use the additional info at my disposal now.

Sam




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