09-25-2013
You can force a process to start out mostly in swap, but if the process runs at all it will wind up in RAM. Running something totally from swap is a bad idea, and if allowed, it results in a real performance drag called thrashing. The swapped process runs 100's of time slower and can seriously degrade the whole system. For every other process on the system.
If you got this idea from seeing how much memory a service is using, you may have misunderstood. A lot of the working set of a process is in shared memory. All processes use this shared memory at the same time. If each of the required system processes (services among them) had nothing but private memory, it likely would have eaten most of system memory before you even logged onto a newly booted box.
You may want to rethink this swap idea.
These 2 Users Gave Thanks to jim mcnamara For This Post:
10 More Discussions You Might Find Interesting
1. Filesystems, Disks and Memory
I need to put a program together to determine the total, available memory and total and available swap on unix machines. I have been searching for weeks and I seem to run into dead ends. Every unix platform I look at has a different way to determine memory info.
Any sugggestions or new... (4 Replies)
Discussion started by: ghe1
4 Replies
2. Solaris
Hi
Can any help me on setting the swap memory ? I would like to set swap memory for installing oracle 9i software.
RAM - 512 Mb
HDD - 40 Gb
OS - Sun Solaris 5.9 (6 Replies)
Discussion started by: sivaramat
6 Replies
3. Solaris
Hi all
Got myself in a pickle here, chasing my own tail and am confused. Im trying to work out memory / swap on my solaris 10 server, that Im using zones on.
Server A has 32Gb of raw memory, ZFS across the root /mirror drives.
# prtdiag -v | grep mem = Memory size: 32768 Megabytes
#... (1 Reply)
Discussion started by: sbk1972
1 Replies
4. UNIX for Dummies Questions & Answers
Hi,
I want to see used swap memory
I know that for this there is command free -m
but this shows Swap: 16383 4529 11854
by top command
while load is 1.05
max CPU % 24 mysqld
why used swap shows 4529
either it is not flushed
there is other command... (2 Replies)
Discussion started by: kaushik02018
2 Replies
5. UNIX for Advanced & Expert Users
Hi,
Please help explain and answer the below:
1. I need to predetermine how much swap will my JVM use if it is started with -Xms 512M and -Xmx 1024M ?
2. Can a JVM process just use the Heap and not the Swap memory ?
3. If the Total physical RAM on my server is 8 GB and current Heap... (6 Replies)
Discussion started by: mohtashims
6 Replies
6. UNIX for Dummies Questions & Answers
hi guys
the monitoring team is using a tool for monitoring linux boxes and they set an alarm for swap memory to 10%(critical) I really has no idea when swap memory usage is high....
Can someone recommend me a threshold for this? when is warning or critical and this parameters can affect... (3 Replies)
Discussion started by: karlochacon
3 Replies
7. UNIX for Dummies Questions & Answers
In Linux, Unix environments Is swap and Shared memory the same ?
In Linux, swap is mounted on /dev/shm ? I am wondering if the naming of 'shm' has anything to do with Shared memory ? (3 Replies)
Discussion started by: kraljic
3 Replies
8. HP-UX
here is the output of swapinfo command
==> swapinfo
Kb Kb Kb PCT START/ Kb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev 8192000 0 8184000 0% 0 - 1 /dev/vg00/swap
reserve - 8184000 -8184000
memory ... (5 Replies)
Discussion started by: mohtashims
5 Replies
9. Linux
Hi,
In our production box i can see the Swap space using the below command
free
total used free shared buffers cached
Mem: 65963232 41041084 24922148 0 877160 35936292
-/+ buffers/cache: 4227632 61735600
Swap: 4192880 ... (6 Replies)
Discussion started by: ratheeshjulk
6 Replies
10. Red Hat
Admins,
How can I configure the server so that it will utilize the swap file as little as possible? Please correct me if I'm wrong, I would say change the value of sysctl - vm.swappiness? And if, how can I keep it permenatly even after rebooting the system? since no related parameters in... (7 Replies)
Discussion started by: leo_ultra_leo
7 Replies
LEARN ABOUT FREEBSD
swapoff
SWAPON(8) BSD System Manager's Manual SWAPON(8)
NAME
swapon, swapoff, swapctl -- specify devices for paging and swapping
SYNOPSIS
swapon [-F fstab] -aLq | file ...
swapoff [-F fstab] -aLq | file ...
swapctl [-AghklmsU] [-a file ... | -d file ...]
DESCRIPTION
The swapon, swapoff and swapctl utilities are used to control swap devices in the system. At boot time all swap entries in /etc/fstab are
added automatically when the system goes multi-user. Swap devices use a fixed interleave; the maximum number of devices is unlimited. There
is no priority mechanism.
The swapon utility adds the specified swap devices to the system. If the -a option is used, all swap devices in /etc/fstab will be added,
unless their ``noauto'' or ``late'' option is also set. If the -L option is specified, swap devices with the ``late'' option will be added
as well as ones with no option. If the -q option is used, informational messages will not be written to standard output when a swap device
is added.
The swapoff utility removes the specified swap devices from the system. If the -a option is used, all swap devices in /etc/fstab will be
removed, unless their ``noauto'' or ``late'' option is also set. If the -L option is specified, swap devices with the ``late'' option will
be removed as well as ones with no option. If the -q option is used, informational messages will not be written to standard output when a
swap device is removed. Note that swapoff will fail and refuse to remove a swap device if there is insufficient VM (memory + remaining swap
devices) to run the system. The swapoff utility must move swapped pages out of the device being removed which could lead to high system
loads for a period of time, depending on how much data has been swapped out to that device.
Other options supported by both swapon and swapoff are as follows:
-F fstab
Specify the fstab file to use.
The swapctl utility exists primarily for those familiar with other BSDs and may be used to add, remove, or list swap devices. Note that the
-a option is used differently in swapctl and indicates that a specific list of devices should be added. The -d option indicates that a spe-
cific list should be removed. The -A and -U options to swapctl operate on all swap entries in /etc/fstab which do not have their ``noauto''
option set.
Swap information can be generated using the swapinfo(8) utility, pstat -s, or swapctl -l. The swapctl utility has the following options for
listing swap:
-h Output values in human-readable form.
-g Output values in gigabytes.
-k Output values in kilobytes.
-m Output values in megabytes.
-l List the devices making up system swap.
-s Print a summary line for system swap.
The BLOCKSIZE environment variable is used if not specifically overridden. 512 byte blocks are used by default.
FILES
/dev/{ada,da}?s?b standard paging devices
/dev/md? memory disk devices
/etc/fstab ASCII file system description table
DIAGNOSTICS
These utilities may fail for the reasons described in swapon(2).
SEE ALSO
swapon(2), fstab(5), init(8), mdconfig(8), pstat(8), rc(8)
HISTORY
The swapon utility appeared in 4.0BSD. The swapoff and swapctl utilities appeared in FreeBSD 5.1.
BSD
November 22, 2013 BSD