Linux Tuning The VM (memory) Subsystem

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Tuning the VM (Virtual Memory) subsystem in Linux can help improve performance in systems with memory-intensive workloads. Here are some general tips to help tune the VM subsystem:

  1. Adjust the swappiness value: The swappiness value determines how aggressively the kernel will swap out memory pages to disk. A value of 0 disables swapping, while a value of 100 will aggressively swap out memory. A good starting point is usually around 10, but you should experiment with different values to find the optimal setting for your workload. You can adjust the swappiness value by running the following command:
sudo sysctl vm.swappiness=10

This will set the swappiness value to 10. To make the change permanent, add the following line to the /etc/sysctl.conf file:

vm.swappiness = 10
  1. Adjust the cache pressure: The vfs_cache_pressure value determines how aggressively the kernel will reclaim memory used by the page cache. A value of 100 will prefer to keep the cache in memory, while a value of 0 will aggressively free up memory used by the cache. A good starting point is usually around 50. You can adjust the vfs_cache_pressure value by running the following command:
sudo sysctl vm.vfs_cache_pressure=50

To make the change permanent, add the following line to the /etc/sysctl.conf file:

vm.vfs_cache_pressure = 50
  1. Adjust the memory allocation: If you have enough memory available, you may want to increase the memory allocation for the kernel by adding the following line to the /etc/sysctl.conf file:
vm.min_free_kbytes = 262144

This sets the minimum amount of free memory that the kernel should maintain to 256MB.

  1. Adjust the I/O scheduler: Depending on your workload, you may want to use a different I/O scheduler. For example, the deadline scheduler is good for database workloads, while the cfq scheduler is good for general-purpose workloads. You can view the current I/O scheduler by running the following command:
cat /sys/block/<DEVICE>/queue/scheduler

Replace <DEVICE> with the name of your disk device (e.g. sda). To change the I/O scheduler, you can add the following line to the /etc/rc.local file:

echo <SCHEDULER> > /sys/block/<DEVICE>/queue/scheduler

Replace <SCHEDULER> with the name of the scheduler you want to use (e.g. deadline), and <DEVICE> with the name of your disk device.

These are just a few examples of how to tune the VM subsystem in Linux. The optimal settings will depend on your workload and hardware, so you should experiment with different values to find the best performance for your system.

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