How To Configure Swappiness
hadoop linux swappiness swap sysctl config
Swappiness is a Linux kernel parameter that controls the relative weight given to swapping out runtime memory, as opposed to dropping pages from the system page cache. Swappiness can be set to values between 0 and 100 inclusive. A low value causes the kernel to avoid swapping, a higher value causes the kernel to try to use swap space. The default value is 60, and for most desktop systems, setting it to 100 may affect the overall performance, whereas setting it lower (even 0) may decrease response latency.
Value Strategy vm.swappiness = 0 The kernel will swap only to avoid an out of memory condition. See the "VM Sysctl documentation". vm.swappiness = 1 Kernel version 3.5 and over, as well as kernel version 2.6.32-303 and over: Minimum amount of swapping without disabling it entirely. vm.swappiness = 10 This value is sometimes recommended to improve performance when sufficient memory exists in a system. vm.swappiness = 60 The default value. vm.swappiness = 100 The kernel will swap aggressively.
With kernel version
3.5 and over, as well as kernel version
2.6.32-303 and over, it is likely better to use
1 for cases where
0 used to be optimal.
To temporarily set the swappiness in Linux, write the desired value (e.g. 10) to
/proc/sys/vm/swappiness using the following command, running as root user.
# Set the swappiness value as root echo 10 > /proc/sys/vm/swappiness # Alternatively, run this sysctl -w vm.swappiness=10 # Verify the change cat /proc/sys/vm/swappiness 10 # Alternatively, verify the change sysctl vm.swappiness vm.swappiness = 10
To find the current swappiness settings, type:
cat /proc/sys/vm/swappiness 60
Swapiness can be a value from 0 to 100.
- Swappiness near 100 means that the operating system will swap often and usually, too soon.
- Although swap provides extra resources, RAM is much faster than swap space. Any time something is moved from RAM to swap, it slows down.
A swappiness value of 0 means that the operating will only rely on swap when it absolutely needs to. We can adjust the swappiness with the sysctl command:
sysctl vm.swappiness=10 vm.swappiness=10
If we check the system swappiness again, we can confirm that the setting was applied:
cat /proc/sys/vm/swappiness 10
To make changes permanent, you can add the setting to the /etc/sysctl.conf file:
sudo nano /etc/sysctl.conf
Add the below line.
# Search for the vm.swappiness setting. Uncomment and change it as necessary. vm.swappiness=10