I need a step-by-step, simple and easy way to configure swappiness.

  • 24
    One liner sudo bash -c "echo 'vm.swappiness = 15' >> /etc/sysctl.conf" May 7, 2014 at 20:45
  • 17
    @redanimalwar you also need to run sudo sysctl -p to load the new swappiness value from the sysctl.conf file, otherwise the change just applies on the next reboot.
    – waldyrious
    Jun 29, 2015 at 14:16

2 Answers 2


The Linux kernel provides a tweakable setting that controls how often the swap file is used, called swappiness.

A swappiness setting of zero means that the disk will be avoided unless absolutely necessary (you run out of memory), while a swappiness setting of 100 means that programs will be swapped to disk almost instantly.

Ubuntu system comes with a default of 60, meaning that the swap file will be used fairly often if the memory usage is around half of my RAM. You can check your own system's swappiness value by running:

one@onezero:~$ cat /proc/sys/vm/swappiness

As I have 4 GB of RAM I'd like to turn that down to 10 or 15. The swap file will then only be used when my RAM usage is around 80 or 90 percent. To change the system swappiness value, open /etc/sysctl.conf as root. Then, change or add this line to the file:

vm.swappiness = 10

Apply the change.

sudo sysctl -p

You can also change the value while your system is still running with:

sysctl vm.swappiness=10

You can also clear your swap by running swapoff -a and then swapon -a as root instead of rebooting to achieve the same effect.

To calculate your swap Formula:

free -m (total) / 100 = A

A * 10

root@onezero:/home/one# free -m
             total       used       free     shared    buffers     cached
Mem:          3950       2262       1687          0        407        952
-/+ buffers/cache:        903       3047
Swap:         1953          0       1953

so total is 3950 / 100 = 39.5 * 10 = 395

So what it mean is that when 10 % (395 MB) of ram is left then it will start using swap.

                                          Help . Ubuntu . Swap

                                           What is swappiness

The swappiness parameter controls the tendency of the kernel to move processes out of physical memory and onto the swap disk. Because disks are much slower than RAM, this can lead to slower response times for system and applications if processes are too aggressively moved out of memory.

  • swappiness can have a value between 0 and 100.
  • swappiness=0:
    • Kernel version 3.5 and newer: disables swapiness.
    • Kernel version older than 3.5: avoids swapping processes out of physical memory for as long as possible.
  • swappiness=1:
    • Kernel version 3.5 and over: minimum swappiness without disabling it entirely.
  • swappiness=100:
    • Tells the kernel to aggressively swap processes out of physical memory and move them to swap cache.

See http://en.wikipedia.org/wiki/Swappiness.

The default setting in Ubuntu is swappiness=60. Reducing the default value of swappiness will probably improve overall performance for a typical Ubuntu desktop installation. A value of swappiness=10 is recommended, but feel free to experiment.


Started using swap at 91%:

enter image description here As I have configured my system & vm to make use of RAM at 90%, at 90% there was no swapping.

After that I opened some applications like Firefox & Shutter, and it started swapping because RAM usage is above 90%.

  • 146
    Swappiness of 100 does not make programs get swapped out immediately, nor does a value of 60 or 90 mean swap gets used when ram is 60 or 90% full. It is a ratio of preference for stealing pages from cache vs. swapping things out to free up some memory when there isn't enough. A low value will strongly prefer stealing pages from the cache, and a high value strongly prefers to try and swap pages out. The setting only has any effect once memory is ( nearly ) all used, and the kernel has to choose how to free some up.
    – psusi
    Feb 13, 2012 at 19:15
  • 77
    You need to point out that the RAM which is NOT occupied by running programs is used as disk cache... so, by decreasing swappiness, you increase the chance of a program not to be swapped out, but at the same time decrease the size of disk cache, which can make disk access slower. So the effects of this setting on the actual performance are not that straightforward... you're welcome to experiment of course but I suspect the defaults are set by people who understand enough in the subject :)
    – Sergey
    Feb 14, 2012 at 0:42
  • 21
    @Sergey and the irony of it is that those with small RAM are most likely to try every trick they can come across to boost performance and are more likely to be the people for whom 60 or even higher would be the best figure. Those of us setting it to 10 because we've tonnes of RAM aren't gaining as much as they'll lose if they do so.
    – Jon Hanna
    Aug 7, 2012 at 1:35
  • 8
    @Freedom_Ben: See linuxatemyram.com :)
    – Sergey
    May 14, 2014 at 7:16
  • 9
    Just leaving a similar discussion here - unix.stackexchange.com/questions/88693/… Nov 4, 2015 at 13:59

For ZRAM swap without any actual swap partitions/files, use 100. It'll pre-compress everything what can be pre-compressed, leaving cache intact and quickly decompress data as needed (also, without real swap you'll need to increase admin_reserve_kbytes x2 or even x4 to avoid whole system freezing on low RAM instead of dropping a hungry application).

For SSD with actual swap partition, use 1. It'll prevent from swapping as long as possible, sacrificing the cache (but cache can be easily re-read from SSD).

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