Set virtual memory in Linux-create and enable Swap zone and linuxswap

Set virtual memory in Linux-create and enable Swap zone and linuxswap

If your server always reports insufficient memory and the service is forced to kill due to insufficient memory, enabling the swap area is a good choice for virtual memory. If it is an SSD hard disk, the normal read/write speed is above 300 MB/S. After swap is enabled, the performance has improved a lot, especially in processing scripts that consume a large amount of memory.

Principle for creating a swap zone:
1. The size of the created swap zone should be greater than the actual physical memory capacity, but not too large, to avoid wasting hard disk space.
2. If memory I/O requests are frequent, and the wait time of the I/O queue in a single swap zone is too long, you can create several more swap zones.
3. In principle, priority should be given to the device with the fastest I/O speed.

Procedure:
1. Create blank files for hard disk storage in the swap area.

12	# Create a 1G blank SWAP swap zone file dd if =/dev/zero of =/SWAP bs = 1 M count = 1024

Generally, 2 ~ physical memory is created ~ 2.5 times the size of the file as the swap area.

2. format the file as a swap file system using mkswap

12	Mkswap-f/swap #-f uses the file as the swap Zone

3. Enable the created Swap file

1	swapon /swap

4. If necessary, you can enable the swap file exchange zone automatically upon startup, modify/etc/fstab, and add a line

1	/Swap defaults 0 0 # enable swap upon startup

5. If you do not need to enable swap or adjust the swap size, you can use the swapoff command to disable swap.

1	swapoff /swap

After swap is disabled, delete the corresponding swap file to delete the swap area. To adjust the size of the swap area, create a new one from the first part.