[CentOS] 2.6 memory management question

[William Warren]

Linux uses all ram for file caching if applications don't use it. 
That's how it works.  If you aren't using swap and your mahcine is 
running fine everything's cool

tblader wrote:
> Hello all.
> I have a centos 4.4 box (2.6.9-42.0.10.ELsmp) with 7gig of ram that
> doesn't seem to be using swap (also 7gig now).  I say "seem" because
> I've noticed ram utilization run around 95% (with oracle and friends
> running) and then firing up a couple apps to use that last 5% will
> stop the machine dead in it's tracks.
> 
> I ran across some reading[0] about /proc/sys/vm/swappiness and how it
> affects the kernels decisions when dealing with swap, but it's not
> all that clear to me whether this is the source of the problem.
> It seems like the kernel just isn't using swap at all.
> 
> I've double checked my swap partition in fstab, ran mkswap again,
> double checked it's availability with vmstat -s  but still it's
> just not getting used.  Sunday, the box died around 3am and sar
> seems to show memory use on the rise right up till it hurled[1]
> (I just stuck another gig in the box monday, so sar only shows
> 6gig on sunday)
> 
> 
> Anyone know whats up with this?
> PS: swap is an LVM partition.
> 
> Thanks
> Thomas
> 
> 
> 
> [0] - http://lwn.net/Articles/83588/
> [1] - sar -A
> 12:00:01 AM kbmemfree kbmemused  %memused kbbuffers  kbcached kbswpfree 
> kbswpused  %swpused  kbswpcad
> ...
> 02:40:01 AM    197656   5909384     96.76    203308   4066344  
> 16383992         0      0.00         0
> 02:50:01 AM    191728   5915312     96.86    203320   4066400  
> 16383992         0      0.00         0
> 03:00:01 AM    185584   5921456     96.96    203336   4067132  
> 16383992         0      0.00         0
> 03:10:01 AM    185712   5921328     96.96    203344   4067872  
> 16383992         0      0.00         0
> Average:       191895   5915145     96.86    203221   4063819  
> 16383992         0      0.00         0
> 
> 
> 12:00:01 AM  pswpin/s pswpout/s
> ...
> 02:00:01 AM      0.00      0.00
> 02:10:01 AM      0.00      0.00
> 02:20:01 AM      0.00      0.00
> 02:30:01 AM      0.00      0.00
> 02:40:01 AM      0.00      0.00
> 02:50:01 AM      0.00      0.00
> 03:00:01 AM      0.00      0.00
> 03:10:01 AM      0.00      0.00
> Average:         0.00      0.00
> 
> 
> 
> 

-- 
My "Foundation" verse:
Isa 54:17  No weapon that is formed against thee shall prosper; and 
every tongue that shall rise against thee in judgment thou shalt 
condemn. This is the heritage of the servants of the LORD, and their 
righteousness is of me, saith the LORD.

-- carpe ductum -- "Grab the tape"
CDTT (Certified Duct Tape Technician)

Linux user #322099
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