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Operating Systems Linux Red Hat High RAM usage, extremely low swapping Post 302624121 by hedkandi on Sunday 15th of April 2012 11:37:01 PM
Old 04-16-2012
High RAM usage, extremely low swapping

Hi team

I have three physical servers running on Red Hat Enterprise Linux Server release 6.2 with the following memory conditions:

Code:
# cat /proc/meminfo | grep -i mem
MemTotal:        8062888 kB
MemFree:          184540 kB
Shmem:               516 kB

and the following swap conditions:

Code:
# cat /proc/meminfo | grep -i swap
SwapCached:          688 kB
SwapTotal:      10305528 kB
SwapFree:       10302584 kB

# cat /proc/sys/vm/swappiness
60

# swapon -s
Filename                                Type            Size    Used    Priority
/dev/dm-1                               partition       10305528        2944    -1

As you can see the swapspace is double the size of memory and yet the swap usage is relatively low compared to actual memory usage:

Code:
# free -mt
                     total       used       free     shared    buffers     cached
Mem:          7873       7693        179          0        380       4241
-/+ buffers/cache:       3071       4802
Swap:        10063          2      10061
Total:       17937       7696      10241

I am trying to understand why the processes are not using swap instead, but relying on RAM until it reached a critical level of 97% last weekend (sorry, haven't got the numbers all I have are charts from nagios) How can I make the process use swap instead of so much of RAM?

Having an aye-karamba moment here
Smilie
 

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SWAPON(8)						     Linux Programmer's Manual							 SWAPON(8)

NAME
swapon, swapoff - enable/disable devices and files for paging and swapping SYNOPSIS
/sbin/swapon [-h -V] /sbin/swapon -a [-v] [-e] /sbin/swapon [-v] [-p priority] specialfile ... /sbin/swapon [-s] /sbin/swapoff [-h -V] /sbin/swapoff -a /sbin/swapoff specialfile ... DESCRIPTION
Swapon is used to specify devices on which paging and swapping are to take place. Calls to swapon normally occur in the system multi-user initialization file /etc/rc making all swap devices available, so that the paging and swapping activity is interleaved across several devices and files. Normally, the first form is used: -h Provide help -V Display version -s Display swap usage summary by device. Equivalent to "cat /proc/swaps". Not available before Linux 2.1.25. -a All devices marked as ``swap'' swap devices in /etc/fstab are made available. Devices that are already running as swap are silently skipped. -e When -a is used with swapon, -e makes swapon silently skip devices that do not exist. -p priority Specify priority for swapon. This option is only available if swapon was compiled under and is used under a 1.3.2 or later kernel. priority is a value between 0 and 32767. See swapon(2) for a full description of swap priorities. Add pri=value to the option field of /etc/fstab for use with swapon -a. Swapoff disables swapping on the specified devices and files. When the -a flag is given, swapping is disabled on all known swap devices and files (as found in /proc/swaps or /etc/fstab). NOTE
You should not use swapon on a file with holes. Swap over NFS may not work. SEE ALSO
swapon(2), swapoff(2), fstab(5), init(8), mkswap(8), rc(8), mount(8) FILES
/dev/hd?? standard paging devices /dev/sd?? standard (SCSI) paging devices /etc/fstab ascii filesystem description table HISTORY
The swapon command appeared in 4.0BSD. Linux 1.x 25 September 1995 SWAPON(8)
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