[ROS] Compiling packages packages encounters slow progress or stuck, use swap

Linux: Ubuntu 18.04 (Bionic Beaver)
ROS: ROS Melodic Morenia

I encounter slow progress or freeze when compiling ROS packages, what should I do?

   When our ROS master is Raspberry Pi, Jetson, etc., the hardware configuration is limited, especially when compiling large programs and running complex algorithms, the 1G and 4G memory on the master control board may not be enough.This is why we need swap (swap swap partition is virtual memory in windows, virtualizing the physical hard disk into memory) to solve the problem of insufficient memory.

swap: is an area on the hard disk.It is part of the machine's virtual memory, which is a combination of accessible physical memory (RAM) and swap space.Swap holds temporarily inactive memory pages.Swap space is used when your OS decides that it needs physical memory for an active process and there is not enough available (unused) physical memory.When this happens, inactive pages in physical memory are moved into swap space, freeing that physical memory for other uses.Note that swap has slower access times (about 10³) depending on the speed of the hard drive.Don't think of it as a complete replacement for physical memory.Swap space can be a dedicated swap partition (recommended), a swap file, or a combination of swap partition and swap file.

Note: There are many guides on how much to swap, often wrong.A common misconception is that swap should be double the ram.This is old advice that worked for Windows 98.

  Ubuntu's default swap space (swap space) is 2G, enter free -m in the terminal to view swap, if the physical memory is enough, it is unnecessaryAdded more.If necessary, before compiling, perform the following operations to temporarily increase the swap space.

1. Create a swap file

The total size of files created by dd is equal to bs * count.This example is 1M*4096 = 4GB.Doing this will take some time.

sudo dd if=/dev/zero of=/swapfile bs=1M count=4096

dd: Copies a file in chunks of the specified size, and performs the specified conversion while copying.

2. Convert Interchange File Format

   Formats the file as swap.

sudo mkswap /swapfile

3. Set swap file permissions

   We need to set the swap file permissions to 600 to prevent other users from being able to read potentially sensitive information from the swap file.

sudo chmod 600 /swapfile

4. Enable swap file

  Open swap

sudo swapon -a /swapfile

5. Mount at boot (not necessary)

   If your device performance is not good, you need to permanently increase the swap space.Take action:

sudo gedit /etc/fstab

Then add /swapfile swap swap defaults 0 0 to the fstab file to automatically start the system at boot.